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Hier aufgeführte Forschungsartikel:
Biogeochemistry - Verlag: Springer
Die Zeitschrift behandelt die globalen Aspekte der Biogeochemie in Form von Arbeiten zum Beispiel über den globalen Kohlenstoff-Zyklus oder den Schwefel-Zyklus. Studien über natürliche und künstliche Ökosysteme werden veröffentlicht, wenn sie zu einem allgemeinen Verständnis der Biogeochemie beitragen.
Bacterial species associated with the dimethylsulfoniopropionate (DMSP)-producing phytoplankton Scrippsiella trochoidea were cultured and identified, with the aim of establishing their ability to metabolise DMSP, dimethylsulfide (DMS) and dimethylsulfoxide
(DMSO). Results demonstrate that of the cultivable bacteria only ?-Proteobacteria were capable of producing DMS from DMSP.
The concentration of DMSP was shown to affect the amount of DMS produced. Lower DMSP concentrations (1.5 ?mol dm?3) were completely assimilated, whereas higher concentrations (10 ?mol dm?3) resulted in increasing amounts of DMS being produced. By contrast to the restricted set of bacteria that metabolised DMSP, ~ 70%
of the bacterial isolates were able to ‘consume’ DMS. However, 98-100% of the DMS removed was accounted for as DMSO. Notably,
a number of these bacteria would only oxidise DMS in the presence of glucose, including members of the ?-Proteobacteria and
Bacteroidetes. The observations from this study, coupled with published field data, identify DMS oxidation to DMSO as a major
transformation pathway for DMS, and we speculate that the fate of DMS and DMSP in the field are tightly coupled to the available
carbon produced by phytoplankton.
Content Type Journal Article
Pages 1-16
DOI 10.1007/s10533-012-9702-7
Authors
Angela D. Hatton, Department of Biogeochemistry & Earth Science, Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll PA37 1QA, UK
Damodar M. Shenoy, Department of Microbial & Molecular Biology, Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll PA37 1QA, UK
Mark C. Hart, Department of Microbial & Molecular Biology, Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll PA37 1QA, UK
Andrew Mogg, Department of Biogeochemistry & Earth Science, Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll PA37 1QA, UK
David H. Green, Department of Microbial & Molecular Biology, Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll PA37 1QA, UK
Dinoflagellates are recognised as one of the major phytoplankton groups that produce dimethylsulphoniopropionate (DMSP), the
precursor of the marine trace gas dimethylsulphide (DMS) which has climate-cooling potential. To improve the prospects for
including dinoflagellates in global climate models that include DMSP-related processes, we increased the data base for this
group by measuring DMSP, DMS-producing enzyme activity (DPEA), carbon, nitrogen and Chl a in nine clonal dinoflagellate cultures (1 heterotrophic and 8 phototrophic strains). Growth rates ranged from 0.11 to 1.92 day?1 with the highest value being for the heterotroph Crypthecodinium cohnii. Overall, we observed two orders of magnitude variability in DMSP content (11–364 mM) and detected DPEA in five of the nine
strains (0.61–59.73 fmol cell?1 h?1). Cell volume varied between 454 and 18,439 ?m3 and whilst C and N content were proportional to the cell volume, DMSP content was not. The first DMSP measurements for a
dinoflagellate from Antarctic waters and a species with diatom-like plastids are included. Lower DMSP concentrations were
found in three small athecate species and a dinoflagellate with haptophyte-like plastids. The highest concentrations and production
rates tended to be in globally distributed dinoflagellates and the heterotroph. Photosynthetic species that are distributed
in temperate to tropical waters showed low DMSP concentrations and production rates and the polar representative showed moderate
concentration and a low production rate. Estuarine species had the lowest concentrations and production rates. These data
should help refine the inclusion of dinoflagellates as a functional group in future global climate models.
Content Type Journal Article
Pages 1-21
DOI 10.1007/s10533-012-9705-4
Authors
A. M. N. Caruana, Laboratory for Global Marine and Atmospheric Chemistry, School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ UK
M. Steinke, Department of Biological Sciences, University of Essex, Colchester, CO4 3SQ UK
S. M. Turner, Laboratory for Global Marine and Atmospheric Chemistry, School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ UK
Gill Malin, Laboratory for Global Marine and Atmospheric Chemistry, School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ UK
The influence of solar ultraviolet radiation and photosynthetically active radiation (PAR) on summertime marine bacterial
uptake and assimilation of sulfur from radiolabeled dimethlysulfoniopropionate (35S-DMSP) was studied at four Arctic and two Antarctic stations. Incubations with 3H-leucine were also conducted for comparative purposes as a measurement of bacterial activity. Arctic waters were characterized
by large numbers of colonial Phaeocystis pouchetii and higher DMSP concentrations than in the two diatom-dominated Antarctic samples. Exposure to full sunlight radiation (280–700 nm),
and to a lesser extent to PAR + UVA (320–700 nm), generally decreased the bacterial assimilation of 3H-leucine with respect to darkness, and caused variable effects on 35S-DMSP assimilation. By using a single-cell approach involving microautoradiography we found high percentages of sulfur assimilating
cells within the bacterial groups Gammaproteobacteria, Bacteroidetes, SAR11 and Roseobacter despite the varying DMSP concentrations between Arctic and Antarctic samples. The dominant SAR11 clade contributed 50–70%
of the cells assimilating both substrates in the Arctic stations, whereas either Gammaproteobacteria or SAR11 were the largest contributors to 3H-leucine uptake in samples from the two Antarctic stations. Only one station was analyzed for single-cell 35S-DMSP assimilation in Antarctica, and Gammaproteobacteria were major contributors to its uptake, providing the first evidence for Antarctic bacteria actively taking up 35S-DMSP. PAR + UVA repeatedly increased the number of SAR11 cells assimilating 3H-leucine. This pattern also occurred with other 35S-DMSP assimilating groups, though not so consistently. Our results support a widespread capability of polar bacteria to assimilate
DMSP-sulfur during the season of maximum DMSP concentrations, and show for the first time that all major polar taxa can be
highly active at this assimilation under the appropriate circumstances. Our findings further confirm the role of sunlight
as a modulator of heterotrophic carbon and sulfur fluxes in the surface ocean.
Content Type Journal Article
Pages 1-18
DOI 10.1007/s10533-012-9699-y
Authors
Clara Ruiz-González, Institut de Ciències del Mar-CSIC, Pg. Marítim de la Barceloneta 37-49, 08003 Barcelona, Catalunya, Spain
Martí Galí, Institut de Ciències del Mar-CSIC, Pg. Marítim de la Barceloneta 37-49, 08003 Barcelona, Catalunya, Spain
Josep M. Gasol, Institut de Ciències del Mar-CSIC, Pg. Marítim de la Barceloneta 37-49, 08003 Barcelona, Catalunya, Spain
Rafel Simó, Institut de Ciències del Mar-CSIC, Pg. Marítim de la Barceloneta 37-49, 08003 Barcelona, Catalunya, Spain
Rapid rainfall events can be responsible for a large proportion of annual nutrient and carbon loading from a watershed. The
bioavailability of organic matter during these rapid loading events increases, suggesting that storms play a relevant role
in the mobilization of potentially labile terrestrial carbon. A high correlation between river discharge rates and dissolved
and particulate nutrient and carbon concentrations during autumn and winter storms was observed in several temperate Pacific
Northwest rivers. Dissolved and particulate lignin concentrations also increased with river discharge; for example, in October
2009 dissolved lignin concentrations increased roughly 240% with a 200% increase in river discharge. During these storms a
unique phenolic composition was observed for dissolved lignin that was rapidly mobilized from surface soils relative to the
base flow of dissolved lignin. The observed increase in Ad/Al ratios with discharge indicates that rapidly mobilized dissolved
lignin is more degraded than the base flow of dissolved lignin. Similarly, a marked increase in C/V ratios and decrease in
the S/V ratio of dissolved lignin phenols with increasing river discharge was observed. These results may indicate a difference
in source between mobilized and base flow pools, or, more likely, preferential degradation and mobilization/retention of specific
lignin phenols. The cumulative results from this year-long data set indicate that a shallow nutrient-rich pool of particulate
and dissolved organic matter accumulates in watersheds during periods of soil-saturation deficiency (summer). Autumn and winter
storms mobilize this pool of accumulated nutrients from surface soils, which is exhausted with successive winter storms.
Content Type Journal Article
Pages 1-17
DOI 10.1007/s10533-012-9700-9
Authors
Nicholas D. Ward, School of Oceanography, University of Washington, P. O. Box 355351, Seattle, WA 98195-5351, USA
Jeffrey E. Richey, School of Oceanography, University of Washington, P. O. Box 355351, Seattle, WA 98195-5351, USA
Richard G. Keil, School of Oceanography, University of Washington, P. O. Box 355351, Seattle, WA 98195-5351, USA
The climatically-important compound dimethylsulfide (DMS) has been reported to be abundant in the Arctic, particularly in
the marginal sea ice zone. Due to these high concentrations, it may play an important role in climate control. A DMS monthly
climatology for July through October was created employing various ocean characteristics and spatial modeling techniques commonly
used for describing species distributions in ecology. Comparisons between observed and predicted values of surface seawater
DMS concentrations led to r2 values of 0.61, 0.87, 0.66, and 0.37 for July, August, September, and October, respectively. Measurement data used for model
development for July through October were variably distributed spatially. For October only, data were sparse and clustered,
resulting in the poor results obtained for this month. Mean sea ice concentration and surface nitrate concentrations were
found to be important predictors of surface seawater DMS concentrations. A negative relationship between sea ice concentration
and DMS, and a two-phase relationship between nitrate and DMS were found. The two-phase relationship may be indicative of
how DMS concentrations are affected when nitrate is the limiting nutrient. From July to September, predicted DMS concentrations
were generally lowest under the sea ice. High monthly DMS concentrations (up to 10.7 nM) were predicted in the seasonal ice
zone. The highest DMS concentrations in September (~2.6 nM) were predicted along the ice edge. In order to create more accurate
climatologies and to increase our understanding of sulfur cycling in the Arctic, a higher spatial and temporal distribution
of DMS measurements is required.
Content Type Journal Article
Pages 1-15
DOI 10.1007/s10533-011-9683-y
Authors
Grant R. W. Humphries, Center for Sustainability: Agriculture, Food, Energy and Environment, University of Otago, Dunedin, New Zealand
Clara J. Deal, International Arctic Research Center, University of Alaska Fairbanks, Fairbanks, AK, USA
Scott Elliott, Division of Computational Sciences, Climate Ocean Sea Ice Modeling, Los Alamos National Laboratory, Los Alamos, NM, USA
Falk Huettmann, EWHALE Lab, Institute of Arctic Biology, Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, USA
The influence of the seasonal development of microplankton communities on the cycling of dimethylsulfide (DMS) and its precursor
dimethylsulfoniopropionate (DMSP) was investigated along a South–North gradient (36–59°N) in the Northwest (NW) Atlantic Ocean. Three surveys allowed the sampling of surface mixed layer (SML) waters at stations
extending from the subtropical gyre to the Greenland Current during May, July and October 2003. Pools and transformation rates
of DMSP and DMS were quantified and related to prevailing physical and biochemical conditions, phytoplankton abundance and
taxonomic composition, as well as bacterioplankton abundance and leucine uptake. The South–North progression of the diatom
bloom, a prominent feature in the NW Atlantic, did not influence the production of DMS whereas conditions in the N Atlantic
Drift lead to a persistent bloom of DMSP-rich flagellate-dominated phytoplankton community and high net DMS production rates.
Macroscale patterns of the observed variables were further explored using principal component analysis (PCA). The first axis
of the PCA showed a strong association between the spatio-temporal distribution of DMSP and the abundance of several phytoplankton
groups including dinoflagellates and prymnesiophytes, as well as with microbial-mediated DMSPd consumption and yields and rates of the conversion of DMSP into DMS. The second axis revealed a strong association between
concentrations of DMS and SML depth and photosynthetically active radiation, a result supporting the prominent role of solar
radiation as a driver of DMS dynamics.
Content Type Journal Article
Pages 1-18
DOI 10.1007/s10533-011-9698-4
Authors
Martine Lizotte, Département de biologie, Québec-Océan, Université Laval, Quebec, QC G1V 0A6, Canada
Maurice Levasseur, Département de biologie, Québec-Océan, Université Laval, Quebec, QC G1V 0A6, Canada
Sonia Michaud, Fisheries and Oceans Canada, Maurice Lamontagne Institute, Mont-Joli, QC G5H 3Z4, Canada
Michael G. Scarratt, Fisheries and Oceans Canada, Maurice Lamontagne Institute, Mont-Joli, QC G5H 3Z4, Canada
Anissa Merzouk, Département de biologie, Québec-Océan, Université Laval, Quebec, QC G1V 0A6, Canada
Michel Gosselin, Institut des sciences de la mer de Rimouski, Université du Québec à Rimouski, 310 Allée des Ursulines, Rimouski, QC G5L 3A1, Canada
Julien Pommier, Laboratoire de Radioécologie de Cherbourg-Octeville, Institut de Radioprotection et de Sureté Nucléaire, Cherbourg-Octeville, 50130 France
Richard B. Rivkin, Ocean Sciences Center, Memorial University of Newfoundland, St-John’s, NF A1C 5S7, Canada
Ronald P. Kiene, Department of Marine Sciences, University of South Alabama, Mobile, AL 36688, USA
Both solar irradiance and primary production have been proposed as independent controls on seawater dimethyl sulphide (DMS)
and dimethylsulphoniopropionate (DMSP) concentrations. However, irradiance also drives photosynthesis, and thus influences
a complex set of inter-related processes that modulate marine DMS. We investigate the potential inter-relationships between
the rate of primary production (carbon assimilation), water-attenuated irradiance and DMS/DMSP dynamics by applying correlation
analysis to a high resolution, concurrently sampled in situ data set from a range of latitudes covering multiple biogeochemical
provinces from 3 of the 4 Longhurst biogeochemical domains. The combination of primary production (PP) and underwater irradiance
(Iz) within a multivariate regression model is able to explain 55% of the variance in DMS concentrations from all depths within
the euphotic zone and 66% of the variance in surface DMS concentrations. Contrary to some previous studies we find a variable
representing biological processes is necessary to better account for the variance in DMS. We find that the inclusion of Iz
accounts for variance in DMS that is independent from the variance explained by PP. This suggests an important role for solar
irradiance (beyond the influence of irradiance upon primary production) in mediating the relationship between the productivity
of the ecosystem, DMS/DMSP production and ambient seawater DMS concentrations.
Content Type Journal Article
Pages 1-13
DOI 10.1007/s10533-011-9697-5
Authors
C. J. Miles, Laboratory for Global Marine and Atmospheric Chemistry (LGMAC), School of Environmental Sciences, University of East Anglia (UEA), Norwich, NR4 7TJ UK
T. G. Bell, Laboratory for Global Marine and Atmospheric Chemistry (LGMAC), School of Environmental Sciences, University of East Anglia (UEA), Norwich, NR4 7TJ UK
P. Suntharalingam, Laboratory for Global Marine and Atmospheric Chemistry (LGMAC), School of Environmental Sciences, University of East Anglia (UEA), Norwich, NR4 7TJ UK
Forest biogeochemical cycles are shaped by effects of dominant tree species on soils, but the underlying mechanisms are not
well understood. We investigated effects of temperate tree species on interactions among carbon (C), nitrogen (N), and acidity
in mineral soils from an experiment with replicated monocultures of 14 tree species. To identify how trees affected these
soil properties, we evaluated correlations among species-level characteristics (e.g. nutrient concentrations in leaf litter,
wood, and roots), stand-level properties (e.g. nutrient fluxes through leaf litterfall, nutrient pools in stemwood), and components
of soil C, N, and cation cycles. Total extractable acidity (aciditytot) was correlated positively with mineral soil C stocks (R2 = 0.72, P < 0.001), such that a nearly two-fold increase in aciditytot was associated with a more than two-fold increase of organic C. We attribute this correlation to effects of tree species
on soil acidification and subsequent mineral weathering reactions, which make hydrolyzing cations available for stabilization
of soil organic matter. The effects of tree species on soil acidity were better understood by measuring multiple components
of soil acidity, including pH, the abundance of hydrolyzing cations in soil solutions and on cation exchange sites, and aciditytot. Soil pH and aciditytot were correlated with proton-producing components of the soil N cycle (e.g. nitrification), which were positively correlated
with species-level variability in fine root N concentrations. Soluble components of soil acidity, such as aluminum in saturated
paste extracts, were more strongly related to plant traits associated with calcium cycling, including leaf and root calcium
concentrations. Our results suggest conceptual models of plant impacts on soil biogeochemistry should be revised to account
for underappreciated plant traits and biogeochemical processes.
Content Type Journal Article
Pages 1-14
DOI 10.1007/s10533-011-9695-7
Authors
Kevin E. Mueller, Intercollege Program in Ecology and Department of Horticulture, Pennsylvania State University, University Park, State College, PA 16802, USA
David M. Eissenstat, Intercollege Program in Ecology and Department of Horticulture, Pennsylvania State University, University Park, State College, PA 16802, USA
Sarah E. Hobbie, Department of Ecology, Evolution and Behavior, University of Minnesota, Saint Paul, MN 55108, USA
Jacek Oleksyn, Institute of Dendrology, Polish Academy of Sciences, 62-035 Kornik, Poland
Andrzej M. Jagodzinski, Institute of Dendrology, Polish Academy of Sciences, 62-035 Kornik, Poland
Peter B. Reich, Department of Forest Resources, University of Minnesota, Saint Paul, MN 55108, USA
Oliver A. Chadwick, Department of Geography, University of California-Santa Barbara, Santa Barbara, CA 93106, USA
Jon Chorover, Department of Soil, Water and Environmental Science, University of Arizona, Tucson, AZ 85721, USA
Atmospheric carbon dioxide (CO2) has increased since the pre-industrial period and is predicted to continue to increase throughout the twenty-first century.
The ocean is a sink for atmospheric CO2 and increased CO2 concentration will change the carbonate equilibrium of seawater and result in lower carbonate ion concentration and lower
pH. This may affect the entire marine biota but in particular calcifying organisms. In this study we investigated the effect
of increased CO2 on the virus host interaction of Emiliania huxleyi as a calcifying organism and of Phaeocystis poucheti as a non- calcifying organism. Both algae were grown in laboratory controlled conditions under past (280 ppmv), present (350 ppmv) and future (700 ppmv)
CO2 concentrations with and without added virus. Increased CO2 had a negative effect on the growth rate of P. pouchetii, but not of E. huxleyi. No impact was found on viral lysis of P. pouchetii while increased burst size and slightly delayed lysis was observed for E. huxleyi with increased CO2. We conclude that this short time study could not confirm earlier reports and our hypothesis of a negative effect of high
CO2 on E. huxleyi growth and E. huxleyi virus production.
Content Type Journal Article
Pages 1-7
DOI 10.1007/s10533-011-9692-x
Authors
Cátia Carreira, Department Biological Oceanography, Royal Netherlands Institute for Sea Research, P.O. Box 59, 1790AB Den Burg, The Netherlands
Mikal Heldal, Department of Biology, University of Bergen, Thormøhlensgt. 53 A/B, P.O. Box 7803, 5020 Bergen, Norway
Gunnar Bratbak, Department of Biology, University of Bergen, Thormøhlensgt. 53 A/B, P.O. Box 7803, 5020 Bergen, Norway
We examined the net exchange of total mercury (THg) and methylmercury (MeHg) between a tidal marsh and its adjacent estuary
over a 1-year period from August 2007 to July 2008. Our objectives were to estimate the importance of tidal salt marshes as
sources and sinks of mercury within the Chesapeake Bay system, and to examine the hydrologic and biogeochemical controls on
mercury fate and transport in tidal marshes. Tidal flows and water chemistry were measured at an established tidal flume at
the mouth of the principal tidal creek of a 3-ha marsh section at the Smithsonian Environmental Research Center. Fluxes were
estimated by combining continuous tidal flow measurement for the entire study year, with discrete, hourly, flow-weighted measurements
of filterable and particulate THg and MeHg, dissolved organic carbon (DOC), and suspended particulate matter (SPM) made over
20 tidal cycles during the year. We found that the marsh was a relatively small net tidal source of MeHg, mainly during the
warmer growing season. We also confirmed that the marsh was a substantial source of DOC to the adjacent estuary. DOC was a
significant predictor of both filterable THg and MeHg fluxes. However, although the marsh was a source of filterable THg,
it was overall a net sink for THg because of particulate trapping. The net per-area annual flux of MeHg from tidal marshes
is greater than other MeHg pathways within Chesapeake Bay. The annual load of MeHg from tidal marshes into Chesapeake Bay,
however, is likely small relative to fluvial fluxes and efflux from bottom sediment. This study suggests that MeHg production
within the tidal marsh has greater consequences for biota inhabiting the marsh than for the efflux of MeHg from the marsh.
Content Type Journal Article
Pages 1-18
DOI 10.1007/s10533-011-9691-y
Authors
Carl P. J. Mitchell, Department of Physical and Environmental Sciences, University of Toronto-Scarborough, 1265 Military Trail, Toronto, ON M1C 1A4, Canada
Thomas E. Jordan, Smithsonian Environmental Research Center, 647 Contees Wharf Road, P.O. Box 28, Edgewater, MD 21037-0028, USA
Andrew Heyes, Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, 1 Williams Street, Solomons, MD 20688, USA
Cynthia C. Gilmour, Smithsonian Environmental Research Center, 647 Contees Wharf Road, P.O. Box 28, Edgewater, MD 21037-0028, USA
Nitrogen (N) and sulphur (S) deposition, as well as altered soil moisture dynamics due to climate change can have large effects
on fen meadow biogeochemistry and vegetation. Their combined effects may differ strongly from their separate effects, since
each process affects different nutrients through different mechanisms. However, the impacts of these environmental problems
are rarely studied in combination. We therefore investigated the separate and interactive effects of current levels of N-
and S-deposition and changes in soil moisture dynamics on fen meadow vegetation. We focused on vegetation biomass and N:P
stoichiometry, including access to soil P through root surface phosphatase activity, in a 3-year factorial addition experiment
in an N-limited rich fen meadow in the Biebrza valley in Poland. We applied 29.5 kg N ha?1 year?1 and 32.1 kg S ha?1 year?1, which correspond to current deposition levels in Western Europe. Changes in soil moisture dynamics due to climate change
were mimicked by amplified drying of the soil in summer. This level of N-deposition had limited effects on plant biomass production
in this rich fen, despite low foliar N:P ratios that suggest N limitation. This level of S-deposition, however, resulted in
decreased vegetation P-uptake and biomass. We also showed that increased summer drought resulted in considerable increases
in vegetation biomass. We found no interactive effects on vegetation biomass or N:P stoichiometry, possibly as a result of
the limited main effects of the separate processes.
Content Type Journal Article
Pages 1-12
DOI 10.1007/s10533-011-9694-8
Authors
Jerry van Dijk, Department of Innovation and Environmental Sciences, Faculty of Geosciences, Utrecht University, P.O. Box 80115, 3508 TC Utrecht, The Netherlands
Bjorn Robroek, Department of Innovation and Environmental Sciences, Faculty of Geosciences, Utrecht University, P.O. Box 80115, 3508 TC Utrecht, The Netherlands
Ignacy Kardel, Department of Hydraulic Engineering, Faculty of Civil and Environmental Engineering, Warsaw University of Life Sciences, ul. Nowoursynowska 159, 02-776 Warsaw, Poland
Martin Wassen, Department of Innovation and Environmental Sciences, Faculty of Geosciences, Utrecht University, P.O. Box 80115, 3508 TC Utrecht, The Netherlands
We measured CO2 concentration and determined evasion rate and piston velocity across the water–air interface in flow-through chambers at
eight stations along two 20 km long streams in agricultural landscapes in Zealand, Denmark. Both streams were 9–18-fold supersaturated
in CO2 with daily means of 240 and 340 ?M in January–March and 130 and 180 ?M in June–August. Annual CO2 medians were 212 ?M in six other streams and 460 ?M in four groundwater wells, while seven lakes were weakly supersaturated
(29 ?M). Air concentrations immediately above stream surfaces were close to mean atmospheric conditions except during calm
summer nights. Piston velocity from 0.4 to 21.6 cm h?1 was closely related to current velocity permitting calculation of evasion rates for entire streams. CO2 evasion rates were highest in midstream reaches (170–1,200 mmol m?2 day?1) where CO2-rich soil water entered fast stream flow, while rates were tenfold lower (25–100 mmol m?2 day?1) in slow-flowing lower reaches. CO2 evasion mainly derived from the input of CO2 in soil water. The variability of CO2 evasion along the two lowland streams covered much of the range in sub-Arctic and temperate streams reported previously.
In budgets for the two stream catchments, loss of carbon from soils via the hydrological cycle was substantial (3.2–5.7 mmol m?2 day?1) and dominated by CO2 consumed to form HCO3? by mineral dissolution (69–76%) and export of organic carbon (15–23%) relative to dissolved CO2 export (7–9%).
Content Type Journal Article
Pages 1-14
DOI 10.1007/s10533-011-9696-6
Authors
Kaj Sand-Jensen, Freshwater Biological Laboratory, Biological Institute, University of Copenhagen, Helsingørsgade 51, 3400 Hillerød, Denmark
Peter Anton Staehr, Freshwater Biological Laboratory, Biological Institute, University of Copenhagen, Helsingørsgade 51, 3400 Hillerød, Denmark
Recent investigations have shown macromolecules, such as cutins, and suberins as effective markers for above and belowground
plant tissues. These biopolyesters contain structural units specific for different litter components and for root biomass.
The aim of this work was to understand the fate of plant organic matter (OM) in Mediterranean forest soils by evaluating the
incorporation of cutin and suberin by measuring specific biomarkers. Soil and plant tissue (leaves, woods and roots) samples
were collected in two mixed Mediterranean forests of Quercus ilex (holm oak) in costal stands in Tuscany (central Italy), which have different ecological and edaphic features. Ester-bound
lipids of mineral and organic horizons and the overlying vegetation were analysed using the saponification method in order
to depolymerise cutins and suberins and release their specific structural units. Cutin and suberin specific aliphatic monomers
were identified and quantified by gas chromatographic techniques. The distribution of cutin and suberin specific monomers
in plant tissue suggested that mid-chain hydroxy acids can be used as leaf-specific markers and ?,?-alkanedioic acids and
?C18:1 as root-specific markers. Differences in the distributions of biomarkers specific for above and belowground plant-derived
OM was observed in the two types of soils, suggesting contrasted degradation, stabilisation and transport mechanisms that
may be related to soil physico-chemical properties. The acidic and dry soil appeared to inhibit microbial activity, favouring
stabilization of leaf-derived compounds, while, in the more fertile soil, protection within aggregates appeared to better
preserve root-derived compounds.
Content Type Journal Article
Pages 1-18
DOI 10.1007/s10533-011-9693-9
Authors
Anna Andreetta, Di.P.S.A. Scienze delle Produzioni Vegetali, del Suolo e dell’Ambiente Agroforestale, Piazzale delle Cascine, 18, 50144 Firenze, Italy
Marie-France Dignac, INRA, Laboratory of Biogeochemistry and Ecology of Continental Ecosystems, UMR Bioemco, CNRS, UPMC, 78850 Thiverval-Grignon, France
Stefano Carnicelli, Di.P.S.A. Scienze delle Produzioni Vegetali, del Suolo e dell’Ambiente Agroforestale, Piazzale delle Cascine, 18, 50144 Firenze, Italy
In Northern Alaska (AK), large variation in biogeochemical cycling exists among landscapes underlain by different aged geologic
substrates deposited throughout the Pleistocene. Younger, less weathered landscapes have higher pH (6.5 vs. 4.5), ten-fold
higher exchangeable cation concentrations, and slower rates of microbial activity than older, more weathered landscapes. To
tease apart the effects of polyvalent cations vs. pH on microbial activity and organic matter solubility and stabilization,
we conducted a soil incubation experiment. We collected soils near Toolik Lake, Alaska from replicated sites along a chronosequence
of landscape ages ranging from 11,000 to 4.8 million years since glaciation and manipulated soil pH and calcium (Ca, the dominant
polyvalent cation across all landscape ages) using a factorial experimental design. As expected, microbial respiration was
inhibited by high Ca concentrations at both pH 6.5 and 4.5. In contrast, soils with circumneutral pH (but similar Ca concentrations)
exhibited higher rates of microbial respiration than soils with acidic pH, opposite of in situ patterns. Manipulated soils
with acidic (4.5) pH (but similar Ca concentrations) exhibited higher cumulative dissolved organic nitrogen (DON) in leachates
than soils with circumneutral (6.5) pH, similar to in situ patterns of leaching among landscape ages, but there was no consistent
effect of pH on dissolved organic carbon (DOC) in leachates across landscape ages. Increasing Ca concentration inhibited cumulative
DOC in leachates at circumneutral pH as expected, but had no effect on DOC or DON in leachates at acidic pH. Our results indicate
that both polyvalent cation concentration and pH likely influence microbial activity in tundra soils, suggesting that heterogeneity
in geochemical factors associated with landscape age should be considered in models of tundra biogeochemistry.
Content Type Journal Article
Pages 1-13
DOI 10.1007/s10533-011-9688-6
Authors
Kyle A. Whittinghill, Department of Ecology, Evolution, and Behavior, University of Minnesota, 100 Ecology, 1987 Upper Buford Circle, Saint Paul, MN 55108, USA
Sarah E. Hobbie, Department of Ecology, Evolution, and Behavior, University of Minnesota, 100 Ecology, 1987 Upper Buford Circle, Saint Paul, MN 55108, USA
We investigated the regulatory effect of salinity on the production of dimethylsulfide (DMS) and methanethiol (MeSH) in estuarine
sediments and the potential interactions with the nitrous oxide (N2O) reductase step of the denitrification pathway. This was achieved by monitoring DMS, MeSH and N2O accumulation in sediment slurries retrieved from a temperate estuary (Ave, NW Portugal). Treatments were performed with
and without amendments of potential sulfur gas precursors, DMSP (0–50 ?M) or methionine (0–500 ?M) at different salinities
(0, 15 and 30 ppt). Experimental increases of salinity inhibited DMS accumulation under both oxic and anoxic incubation conditions,
and the pattern was observed whether DMSP or methionine was added or not, i.e. lower salinities stimulated DMS net production.
In contrast, MeSH tended to accumulate to higher concentrations in higher salinity treatments (15 and 30 ppt). Our results
also suggest that while salinity had a direct influence on N2O accumulation, it also may modulated N2O production through its regulatory effect on the formation of MeSH, a compound previously shown to inhibit N2O reduction activity. Overall, our results suggest that changes in salinity may have an important regulatory role in net production
of DMS, MeSH and N2O and their potential emissions to the atmosphere.
Content Type Journal Article
Pages 1-12
DOI 10.1007/s10533-011-9690-z
Authors
C. Magalhães, CIMAR/CIIMAR—Centre of Marine and Environmental Research, University of Porto, Rua dos Bragas, no 289, 4050-123 Porto, Portugal
P. Salgado, CIMAR/CIIMAR—Centre of Marine and Environmental Research, University of Porto, Rua dos Bragas, no 289, 4050-123 Porto, Portugal
R. P. Kiene, Department of Marine Sciences, University of South Alabama, LSCB 25, Mobile, AL 36688, USA
A. A. Bordalo, CIMAR/CIIMAR—Centre of Marine and Environmental Research, University of Porto, Rua dos Bragas, no 289, 4050-123 Porto, Portugal
Grasslands store substantial amounts of carbon in the form of organic matter in soil and roots. At high latitudes and elevation,
turnover of these materials is slow due to various interacting biotic and abiotic constraints. Reliable estimates on the future
of belowground carbon storage in cold grassland soils thus require quantitative understanding of these factors. We studied
carbon turnover of roots, labile coarse particulate organic matter (cPOM) and older non-cPOM along a natural pH gradient (3.9–5.9)
in a subalpine grassland by utilizing soil fractionation and radiocarbon dating. Soil carbon stocks and root biomass, turnover,
and decomposability did not scale with soil pH whereas mean residence times of both soil organic matter fractions significantly
increased with declining pH. The effect was twice as strong for non-cPOM, which was also stronger enriched in 15N at low pH. Considering roots as important precursors for cPOM, the weaker soil pH effect on cPOM turnover may have been
driven by comparably high root pH values. At pH < 5, long non-cPOM mean residence times were probably related to pH dependent
changes in substrate availability. Differences in turnover along the pH gradient were not reflected in soil carbon stocks
because aboveground productivity was lower under acidic conditions and, in turn, higher inputs from aboveground plant residues
compensated for faster soil carbon turnover at less acidic pH. In summary, the study provides evidence for a strong and differential
regulatory role of pH on the turnover of soil organic matter that needs consideration in studies aiming to quantify effects
of changing environmental conditions on belowground carbon storage.
Content Type Journal Article
Pages 1-11
DOI 10.1007/s10533-011-9689-5
Authors
Jens Leifeld, Agroscope Reckenholz-Tänikon Research Station ART, Air Pollution/Climate Group, Reckenholzstrasse 191, 8046 Zurich, Switzerland
Seraina Bassin, Agroscope Reckenholz-Tänikon Research Station ART, Air Pollution/Climate Group, Reckenholzstrasse 191, 8046 Zurich, Switzerland
Franz Conen, Institute for Environmental Geosciences, University of Basel, Bernoullistrasse 30, 4056 Basel, Switzerland
Irka Hajdas, Laboratory of Ion Beam Physics ETH, Schafmattstr. 20, 8093 Zurich, Switzerland
Markus Egli, Department of Geography, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
Jürg Fuhrer, Agroscope Reckenholz-Tänikon Research Station ART, Air Pollution/Climate Group, Reckenholzstrasse 191, 8046 Zurich, Switzerland
Dissolved and particulate organic matter (POM) of three Quebec boreal reservoirs of different ages (Laforge-1, 7 years; Robert-Bourassa,
25 years and Cabonga, 70 years at the time of sampling) and sets of lakes from the same watersheds was analyzed using organic
carbon concentrations, C/N and C/P elemental composition, ?13C and ?15N isotopic values. The reservoirs are characterized by lower dissolved organic carbon concentrations with lower C/N ratios
and by lower ?13C and higher ?15N in POM. They contain more autochthonous dissolved organic matter and less terrigenous organic matter than the lakes. Some
of those characteristics are more pronounced in the younger than in the older reservoirs. The differences can be attributed
to two causes: (1) more extended degradation of terrigenous organic matter, caused by an increase in residence time; and (2)
differences in food web structure resulting from the phenomenon known as trophic upsurge, in newly flooded reservoirs. The
results indicate that some effects of reservoir creation on the carbon cycle are short term perturbations, others however
long term features of those reservoirs. The implications of these findings for CO2 emissions from reservoirs are discussed.
Content Type Journal Article
Pages 1-14
DOI 10.1007/s10533-011-9687-7
Authors
Sebastian Weissenberger, Institut des Sciences de l’Environnement, Université du Québec à Montréal, C.P. 8888, Succursale Centre-Ville, Montreal, QC H3C 3P8, Canada
Marc Lucotte, Institut des Sciences de l’Environnement, Université du Québec à Montréal, C.P. 8888, Succursale Centre-Ville, Montreal, QC H3C 3P8, Canada
René Canuel, Institut des Sciences de l’Environnement, Université du Québec à Montréal, C.P. 8888, Succursale Centre-Ville, Montreal, QC H3C 3P8, Canada
Production of dimethyl sulfide (DMS) from marine samples is often quantified using gas chromatography techniques. Typically,
these are labour intensive and have a slow sample turnover rate. Here we demonstrate the use of a portable fast DMS sensor
(FDS) that utilises the chemiluminescent reaction of DMS and ozone to measure DMS production in aqueous samples, with a maximum
frequency of 10 Hz. We have developed a protocol for quantifying DMS production that removes potential signal interference
from other biogenic trace gases such as isoprene (2-methyl-1,3-butadiene) and hydrogen sulfide. The detection limit was 0.89 pM
(0.02 ppbv) when using a DMS standard gas mixture. The lowest DMS production rates quantified with the FDS and verified using
conventional gas chromatography with flame photometric detection (GC-FPD) were around 0.01 nmol min?1. There was a strong correlation in DMS production when comparing the FDS and GC-FPD techniques with a range of marine samples
(e.g., r2 = 0.94 for Emiliania huxleyi). However, the combined dataset showed the FDS measured 22% higher DMS production than the GC-FPD, with the differences in
rates likely due to interfering gases, for example hydrogen sulfide and isoprene. This possible overestimation of DMS production
is smaller than the two-fold difference in DMS production between day and night samples from a culture of E. huxleyi. The response time of the instrument to changes in DMS production is method dependent (e.g., geometry of incubation vessel,
bubble size) and was approximately 4 min under our conditions when using a culture of E.huxleyi (800 ml) with aeration at 100 ml min?1. We suggest the FDS can reduce sample handling, is suitable for short- and long-term measurements of DMS production in algal
cultures, and will widen the range of DMS research in marine environments.
Content Type Journal Article
Pages 1-10
DOI 10.1007/s10533-011-9678-8
Authors
Benjamin C. Green, Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK
David J. Suggett, Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK
Alan Hills, Hills-Scientific, Boulder, CO 80302, USA
Michael Steinke, Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK
Carbon dynamics during litter decomposition have been described in a variety of forest ecosystems and provided insights into
carbon flow in soils. To quantitatively assess how decomposition processes vary between litter types, solid-state 13C cross-polarization and magic-angle spinning nuclear magnetic resonance (CPMAS NMR) technique was applied to analyze conifer
(cedar, cypress) and hardwood (chinquapin, beech, oak, birch) litter which had degraded during a 3 year litterbag experiment
throughout Japan. The results were used to identify compositional changes and estimate decomposition constants (k values) in exponential equations. Total litter and carbon type mass losses during decomposition varied significantly between
litter types, being affected by the initial physicochemical litter quality. Concomitant increases and decreases in carbonyl
and O/N-alkyl C compositions, respectively, were observed for all litter types, but aromatic and aliphatic C dynamics were less consistent.
In hardwoods, [aromatic/aliphatic C ratio] was generally stable during decomposition, suggesting that, in hardwoods, the decomposabilities
of aromatic and aliphatic C were similar. In the conifers, an increasing [aromatic/aliphatic C ratio] during decomposition
suggested that aromatic C was more recalcitrant than aliphatic C. These results suggest that different decomposition processes
between litter types might be related to different aromatic and aliphatic C behaviors, as affected by lignin stability and
lipid leachability and biosynthesis. Variations in the k values for total litter and carbon types were not obvious between litter types, although the mass loss patterns differed
significantly. The k values estimated in this study may contribute to predictions of soil carbon dynamics and the validation of carbon compartment
models in forest ecosystems.
Content Type Journal Article
Pages 1-15
DOI 10.1007/s10533-011-9682-z
Authors
Kenji Ono, Tohoku Research Center, Forestry and Forest Products Research Institute, 92-25, Shimokuriyagawa, Morioka, Iwate 020-0123, Japan
Syuntaro Hiradate, National Institute for Agro-Environmental Sciences, 3-1-3 Kan-nondai, Tsukuba, Ibaraki 305-8604, Japan
Sayaka Morita, National Institute for Agro-Environmental Sciences, 3-1-3 Kan-nondai, Tsukuba, Ibaraki 305-8604, Japan
Keizo Hirai, Tohoku Research Center, Forestry and Forest Products Research Institute, 92-25, Shimokuriyagawa, Morioka, Iwate 020-0123, Japan
Atmospheric deposition of nitrogen (N) compounds is the major source of anthropogenic N to most upland ecosystems, where leaching
of nitrate (NO3?) into surface waters contributes to eutrophication and acidification as well as indicating an excess of N in the terrestrial
catchment ecosystems. Natural abundance stable isotopes ratios, 15N/14N and 18O/16O (the “dual isotope” technique) have previously been used in biogeochemical studies of alpine and forested ecosystems to
demonstrate that most of the NO3? in upland surface waters has been microbially produced. Here we present an application of the technique to four moorland
catchments in the British uplands including a comparison of lakes and their stream inflows at two sites. The NO3? concentrations of bulk deposition and surface waters at three sites are very similar. While noting the constraints imposed
by uncertainty in the precise ?18O value for microbial NO3?, however, we estimate that 79–98% of the annual mean NO3? has been microbially produced. Direct leaching of atmospheric NO3? is a minor component of catchment NO3? export, although greater than in many similar studies in forested watersheds. A greater proportion of atmospheric NO3? is seen in the two lake sites relative to their inflow streams, demonstrating the importance of direct NO3? deposition to lake surfaces in catchments where terrestrial ecosystems intercept a large proportion of deposited N. The dominance
of microbial sources of NO3? in upland waters suggests that reduced and oxidised N deposition may have similar implications in terms of contributing to
NO3? leaching.
Content Type Journal Article
Pages 1-20
DOI 10.1007/s10533-011-9686-8
Authors
Chris J. Curtis, Environmental Change Research Centre, Geography Department, University College London, Gower Street, London, WC1E 6BT UK
Timothy H. E. Heaton, NERC Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Nottingham, NG12 5GG UK
Gavin L. Simpson, Environmental Change Research Centre, Geography Department, University College London, Gower Street, London, WC1E 6BT UK
Chris D. Evans, Centre for Ecology and Hydrology, Environment Centre Wales, Deiniol Road, Bangor, Wales, LL57 2UW UK
James Shilland, Environmental Change Research Centre, Geography Department, University College London, Gower Street, London, WC1E 6BT UK
Simon Turner, Environmental Change Research Centre, Geography Department, University College London, Gower Street, London, WC1E 6BT UK
Ambient aerosols collected from the marine atmospheric boundary layer of the Bay of Bengal and the Arabian Sea have been studied
to assess the fractional solubility of aerosol iron, defined as Fews (%) = Fews/FeTot × 100; where FeTot is total aerosol iron and Fews is water soluble iron. The mass concentration of FeTot over the two oceanic regions is not significantly different. However, the fractional solubility is 1–2 orders of magnitude
higher over the Bay of Bengal (1.4–24%) compared to that over the Arabian Sea (0.02–0.4%). The spatio-temporal variability
in Fews (%) is attributed to differences in the nature of the mineral dust over the two oceanic regions. The Arabian Sea receives
coarse dust from desert regions; whereas transport of alluvial dust from the Indo-Gangetic Plain is a dominant source to the
Bay of Bengal. The poor fractional solubility (<1%) of Fe from mineral dust, hitherto overestimated in the literature, is
documented for the Arabian Sea. A significant linear relationship (P-value < 0.001) between Fews (%), FeTot and nss-SO42? over the Bay of Bengal provides evidence for the chemical processing of mineral dust. Furthermore, the role of anthropogenic
sources (biomass burning and fossil-fuel combustion) in enhancing the Fews (%) is discernible from the chemical composition of fine mode (PM2.5) aerosols over the Bay of Bengal. The potential impact of these Fe-dust depositions on phytoplankton carbon fixation and
surface ocean biogeochemistry is discussed.
Content Type Journal Article
Pages 1-12
DOI 10.1007/s10533-011-9680-1
Authors
Bikkina Srinivas, Physical Research Laboratory, Ahmedabad, 380 009 India
M. M. Sarin, Physical Research Laboratory, Ahmedabad, 380 009 India
Ashwini Kumar, Physical Research Laboratory, Ahmedabad, 380 009 India
The carbon pool of peatlands has been considered as potentially unstable in a changing climate. This study is the first presenting
carbon dioxide (CO2) net ecosystem exchange, CO2 efflux due to ecosystem respiration and CO2 uptake by gross primary production over a complete growing season for different microforms of a boreal peatland in Russia
(61°56?N, 50°13?E). CO2 fluxes were measured using the closed chamber technique from the 25th April in the period of snow melt until the end of the
vegetation period and the first frost on the 20th October 2008 at seven different microform types: minerogenous and ombrogenous
hollows, lawns and hummocks, respectively, and Carex lawns situated in a transition zone between minerogenous and ombrogenous mire parts. The total number of chamber flux measurements
was 5,517. Ombrogenous hummocks and lawns were sources of CO2 over the investigation period whereas hollows and minerogenous lawns were CO2 sinks. Some plots of Carex lawns and minerogenous hummocks were sinks while other plots of these microform types were sources. The CO2 fluxes were characterised by large variability not only between the microform types but also within the respective microform
types. Of all microform types, the Carex, ombrogenous, and minerogenous lawns showed the highest variability in CO2 fluxes, which is probably related to a stronger within-microform heterogeneity in vegetation composition and coverage as
well as in the water table level. Air temperature was one of the dominant controls on the CO2 flux dynamics. Water table and green area index were found to have strong influence on CO2 fluxes both within different patches of the same microform type as well as between different microforms.
Content Type Journal Article
Pages 1-29
DOI 10.1007/s10533-011-9684-x
Authors
Julia Schneider, Institute of Botany and Landscape Ecology, Ernst Moritz Arndt University Greifswald, Grimmer Straße 88, 17487 Greifswald, Germany
Lars Kutzbach, Institute of Soil Science, KlimaCampus, University of Hamburg, Allende-Platz 2, 20146 Hamburg, Germany
Martin Wilmking, Institute of Botany and Landscape Ecology, Ernst Moritz Arndt University Greifswald, Grimmer Straße 88, 17487 Greifswald, Germany
Land use changes such as savannah afforestation with eucalypts impact the soil carbon (C) balance, therefore affecting soil
CO2 efflux (Fs), a major flux in the global C cycle. We tested the hypothesis that Fs increases with stand age after afforestation, due to an increasing input of fresh organic matter to the forest floor. In
a Eucalyptus plantation established on coastal savannahs in Congo, bimonthly measurements of Fs were carried out for 1 year on three adjacent stands aged 0.9, 4.4 and 13.7 years and presenting similar growth patterns.
Litterfall and litter accumulation on the forest floor were quantified over a chronosequence. Equations were derived to estimate
the contribution of litter decomposition to Fs throughout the rotation. Litterfall increased with stand age after savannah afforestation. Fs, that was strongly correlated on a seasonal basis with soil water content (SWC) in all stands, decreased between ages 0.9 year
and 4.4 years due to savannah residue depletion, and increased between ages 4.4 years and 13.7 years, mainly because of an
increasing amount of decomposing eucalypt litter. The aboveground litter layer therefore appeared as a major source of CO2, whose contribution to Fs in old stands was estimated to be about four times higher than that of the eucalypt-derived soil organic C pool. The high
litter contribution to Fs in older stands might explain why 13.7 years-old stand Fs was limited by moisture all year round whereas SWC did not limit Fs for large parts of the year in the youngest stands.
Content Type Journal Article
Pages 1-19
DOI 10.1007/s10533-011-9685-9
Authors
Yann Nouvellon, CIRAD, UMR Eco&Sols, Bât 12, 2 Place Viala, 34060 Montpellier Cedex 2, France
Daniel Epron, CIRAD, UMR Eco&Sols, Bât 12, 2 Place Viala, 34060 Montpellier Cedex 2, France
Claire Marsden, CIRAD, UMR Eco&Sols, Bât 12, 2 Place Viala, 34060 Montpellier Cedex 2, France
Antoine Kinana, CRDPI, BP 1291, Pointe-Noire, Republic of Congo
Guerric Le Maire, CIRAD, UMR Eco&Sols, Bât 12, 2 Place Viala, 34060 Montpellier Cedex 2, France
Philippe Deleporte, CIRAD, UMR Eco&Sols, Bât 12, 2 Place Viala, 34060 Montpellier Cedex 2, France
Laurent Saint-André, CIRAD, UMR Eco&Sols, Bât 12, 2 Place Viala, 34060 Montpellier Cedex 2, France
Jean-Pierre Bouillet, CIRAD, UMR Eco&Sols, Bât 12, 2 Place Viala, 34060 Montpellier Cedex 2, France
Jean-Paul Laclau, CIRAD, UMR Eco&Sols, Bât 12, 2 Place Viala, 34060 Montpellier Cedex 2, France
Microbial oxidation in aerobic soils is the primary biotic sink for atmospheric methane (CH4), a powerful greenhouse gas. Although tropical forest soils are estimated to globally account for about 28% of annual soil
CH4 consumption (6.2 Tg CH4 year?1), limited data are available on CH4 exchange from tropical montane forests. We present the results of an extensive study on CH4 exchange from tropical montane forest soils along an elevation gradient (1,000, 2,000, 3,000 m) at different topographic
positions (lower slope, mid-slope, ridge position) in southern Ecuador. All soils were net atmospheric CH4 sinks, with decreasing annual uptake rates from 5.9 kg CH4–C ha?1 year?1 at 1,000 m to 0.6 kg CH4–C ha?1 year?1 at 3,000 m. Topography had no effect on soil atmospheric CH4 uptake. We detected some unexpected factors controlling net methane fluxes: positive correlations between CH4 uptake rates, mineral nitrogen content of the mineral soil and with CO2 emissions indicated that the largest CH4 uptake corresponded with favorable conditions for microbial activity. Furthermore, we found indications that CH4 uptake was N limited instead of inhibited by NH4+. Finally, we showed that in contrast to temperate regions, substantial high affinity methane oxidation occurred in the thick
organic layers which can influence the CH4 budget of these tropical montane forest soils. Inclusion of elevation as a co-variable will improve regional estimates of
methane exchange in these tropical montane forests.
Content Type Journal Article
Pages 1-15
DOI 10.1007/s10533-011-9681-0
Authors
Katrin Wolf, Büsgen Institute-Soil Science of Tropical and Subtropical Ecosystems, Georg-August University of Göttingen, Büsgenweg 2, 37077 Göttingen, Germany
Heiner Flessa, Johann Heinrich von Thünen-Institut, Federal Research Institute for Rural Areas, Forestry and Fisheries, Institute of Agricultural Climate Research, Braunschweig, Germany
Edzo Veldkamp, Büsgen Institute-Soil Science of Tropical and Subtropical Ecosystems, Georg-August University of Göttingen, Büsgenweg 2, 37077 Göttingen, Germany
Organic carbon (C) associated with fine soil particles (<20 ?m) is relatively stable and accounts for a large proportion of
total soil organic C (SOC). The soil C saturation concept proposes a maximal amount of SOC that can be stabilized in the fine
soil fraction, and the soil C saturation deficit (i.e., the difference between current SOC and the maximal amount) is presumed
to affect the capacity, magnitude, and rate of SOC storage. In this study, we argue that predictions using current models
underestimate maximal organic C stabilization of fine soil particles due to fundamental limitations of using least-squares
linear regression. The objective was to improve predictions of maximal organic C stabilization by using two alternative approaches;
one mechanistic, based on organic C loadings, and one statistical, based on boundary line analysis. We collected 342 data
points on the organic C content of fine soil particles, fine particle mass proportions in bulk soil, dominant soil mineral
types, and land use types from 32 studies. Predictions of maximal organic C stabilization using linear regression models are
questionable because of the use of data from soils that may not be saturated in SOC and because of the nature of regression
itself, resulting in a high proportion of presumed over-saturated samples. Predictions of maximal organic C stabilization
using the organic C loading approach fit the data for soils dominated by 2:1 minerals well, but not soils dominated by 1:1
minerals; suggesting that the use of a single value for specific surface area, and therefore a single organic C loading, to
represent a large dataset is problematic. In boundary line analysis, only data representing soils having reached the maximal
amount (upper tenth percentile) were used. The boundary line analysis estimate of maximal organic C stabilization (78 ± 4 g
C kg?1 fraction) was more than double the estimate by the linear regression approach (33 ± 1 g C kg?1 fraction). These results show that linear regression models do not adequately predict maximal organic C stabilization. Soil
properties associated with soil mineralogy, such as specific surface area and organic C loading, should be incorporated to
generate more mechanistic models for predicting soil C saturation, but in their absence, statistical models should represent
the upper envelope rather than the average value.
Content Type Journal Article
Pages 1-13
DOI 10.1007/s10533-011-9679-7
Authors
Wenting Feng, Department of Earth & Environmental Science, University of Pennsylvania, Hayden Hall, 240 South 33rd Street, Philadelphia, PA 19104-6316, USA
Alain F. Plante, Department of Earth & Environmental Science, University of Pennsylvania, Hayden Hall, 240 South 33rd Street, Philadelphia, PA 19104-6316, USA
Johan Six, Department of Plant Sciences, University of California, Davis, CA 95616, USA
Long-lived soil organic matter (SOM) pools are critical for the global carbon (C) cycle, but challenges in isolating such
pools have inhibited understanding of their dynamics. We physically isolated particulate (>53 ?m), silt-, and clay-sized organic
matter from soils collected over two decades from a perennial C3 grassland established on long-term agricultural soil with a predominantly C4 isotopic signature. Silt- and clay-sized fractions were then subjected to a sequential chemical fractionation (acid hydrolysis
followed by peroxide oxidation) to isolate long-lived C pools. We quantified 14C and the natural 13C isotopic label in the resulting fractions to identify and evaluate pools responsible for long-lived SOM. After removal of
particulate organic matter (~14% of bulk soil C) sequential chemical treatment removed 80% of mineral-associated C. In all
mineral-associated fractions, at least 55% of C4-derived C was retained 32 years after the switch to C3 inputs. However, C3–C increased substantially beginning ~25 years after the switch. Radiocarbon-based turnover times ranged from roughly 1200–3000 years
for chemically resistant mineral-associated pools, although some pools turned over faster under C3 grassland than in a reference agricultural field, indicating that new material had entered some pools as early as 14 years
after the vegetation switch. These findings provide further evidence that SOM chemistry does not always reflect SOM longevity
and resistance to microbial decomposition. Even measureable SOM fractions that have extremely long mean turnover times (>1500 years)
can have a substantial component that is dynamic over much shorter timescales.
Content Type Journal Article
Pages 1-15
DOI 10.1007/s10533-011-9673-0
Authors
Sarah L. O’Brien, Department of Biological Sciences, University of Illinois at Chicago, 845 West Taylor Street M/C 066, Chicago, IL 60607, USA
Julie D. Jastrow, Biosciences Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA
Karis J. McFarlane, Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94551, USA
Thomas P. Guilderson, Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94551, USA
Miquel A. Gonzalez-Meler, Department of Biological Sciences, University of Illinois at Chicago, 845 West Taylor Street M/C 066, Chicago, IL 60607, USA
In response to decreasing atmospheric emissions of sulfur (S) since the 1970s there has been a concomitant decrease in S deposition
to watersheds in the Northeastern U.S. Previous study at the Hubbard Brook Experimental Forest, NH (USA) using chemical and
isotopic analyzes (
d34 \textS\textSO4
) combined with modeling has suggested that there is an internal source of S within these watersheds that results in a net
loss of S via sulfate in drainage waters. The current study expands these previous investigations by the utilization of ?18O analyzes of precipitation sulfate and streamwater sulfate. Archived stream and bulk precipitation samples at the Hubbard
Brook Experimental Forest from 1968–2004 were analyzed for stable oxygen isotope ratios of sulfate (
d18 \textO\textSO4
). Overall decreasing temporal trends and seasonally low winter values of
d18 \textO\textSO4
in bulk precipitation are most likely attributed to similar trends in precipitation
d18 \textO\textH2 \textO
values. Regional climate trends and changes in temperature control precipitation
d18 \textO\textH2 \textO
values that are reflected in the
d18 \textO\textSO4
values of precipitation. The significant relationship between ambient temperature and the
d18 \textO\textH2 \textO
values of precipitation is shown from a nearby site in Ottawa, Ontario (Canada). Although streamwater
d18 \textO\textSO4
values did not reveal temporal trends, a large difference between precipitation and streamwater
d18 \textO\textSO4
values suggest the importance of internal cycling of S especially through the large organic S pool and the concomitant effect
on the
d18 \textO\textSO4
values in drainage waters.
Content Type Journal Article
Pages 1-12
DOI 10.1007/s10533-011-9670-3
Authors
Gretchen R. Miles, State University of New York College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, NY 13210-2788, USA
Myron J. Mitchell, State University of New York College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, NY 13210-2788, USA
Bernhard Mayer, Department of Geoscience, University of Calgary, Calgary, AB T2N 1N4, Canada
Gene Likens, Cary Institute of Ecosystem Studies, 2801 Sharon Turnpike, Millbrook, NY 12545-0129, USA
Jeffrey Welker, Environment and Natural Resources Institute, University of Alaska Anchorage, 3211 Providence Dr., Anchorage, AK 99508-4614, USA
Microcosms with Pinus sylvestris seedlings in symbiosis with the fungus mycorrhizal Paxillus involutus were established, and atomic force microscopy (AFM) was used to characterise plant photosynthate-driven fungal interactions
with mineral surfaces. Comparison of images of the same area of the minerals before and after mycorrhizal fungal colonization
showed extensive growth of hyphae on three different mineral surfaces – hornblende, biotite and chlorite. A layer of biological
exudate, or biolayer, covered the entire mineral surface and was composed of globular features of diameter 10–80 nm, and the
morphology of the biolayer differed among mineral types. Similar-sized components were found on the fungal hyphae, but with
a more elongated profile. Biolayer and hyphae surfaces both appeared to be hydrophobic with the hyphal surfaces yielding higher
maximal adhesive interactions and a wider range of values: the mean (± SE) adhesive forces were 2.63 ± 0.03 and 3.46 ± 0.18 nN
for biolayer and hypha, respectively. The highest adhesion forces are preferentially localized at the hyphal surface above
the Spitzenkörper region and close to the tip, with a mean interaction force in this locality of 5.24 ± 0.49 nN. Biolayer
thickness was between 10 and 40 nm. The underlying mineral was easily broken up by the tip, in contrast to the native mineral.
These observations of mineral surfaces colonised by mycorrhizal fungus demonstrate how fungal hyphae are able to form a layer
of organic exudates, or biolayer, and its role in hyphal attachment and potential weathering of ferromagnesian silicates,
which may supply nutrients to the plant.
Content Type Journal Article
Pages 1-15
DOI 10.1007/s10533-011-9667-y
Authors
Loredana Saccone, H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL UK
Salvatore A. Gazzè, H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL UK
Adele L. Duran, Department of Animal and Plant Sciences, Alfred Denny Building, University of Sheffield, Western Bank, Sheffield, S10 2TN UK
Jonathan R. Leake, Department of Animal and Plant Sciences, Alfred Denny Building, University of Sheffield, Western Bank, Sheffield, S10 2TN UK
Steven A. Banwart, Department of Civil and Structural Engineering, Kroto Research Institute, North Campus, University of Sheffield, Broad Lane, Sheffield, S3 7HQ UK
Kristín Vala Ragnarsdóttir, Faculty of Earth Sciences, School of Engineering and Natural Sciences, University of Iceland, Askja, 107 Reykjavik, Iceland
Mark M. Smits, Environmental Biology, Hasselt University, Campus Diepenbeek, Agoralaan – Gebouw D, 3590 Diepenbeek, Belgium
Terence J. McMaster, H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL UK
During the last decade the number of seawater dimethylsulfide (DMS) concentration measurements has increased substantially.
The importance this gas, emitted from the ocean to the atmosphere, may have in the cloud microphysics and hence in the Earth
albedo and radiation budget, makes it necessary to accurately reproduce the global distribution. Recently, the monthly global
DMS climatology has been updated taking advantage of the threefold increased size and better resolved distribution of the
observations available in the DMS database. Here, the emerging patterns found with the previous versions of the database and
climatology are explored with the updated versions. The statistical relationships between the seasonalities of DMS concentrations
and other variables are re-examined. The positive correlation previously found between surface seawater DMS and the daily-averaged
climatological solar radiation dose in the upper mixed layer of the open ocean is confirmed with both the updated DMS database
and climatology. Re-examination of the latitudinal match-mismatch between the seasonalities of DMS and phytoplankton, represented
by the chlorophyll a concentration, reveals that they are highly positively correlated in latitudes higher than 40°, but anti-correlated in the
20°–40° latitudinal bands of both hemispheres. Overall, these global emerging patterns provide key information to further
understanding the factors that control the emission of volatile sulfur from the ocean. The large uncertainties associated
with the methodologies used in global computations, however, call for caution in using these emerging patterns as predictive
tools, and prompt to the design of time series and process-oriented studies aimed at testing the validity of the observed
relationships.
Soil salinity and fluctuations in soil matric potential are stressors for soil microorganisms which, in turn, may affect soil
organic matter turnover. In response to salinity and low soil water content, many microorganisms accumulate osmolytes. Therefore,
it is conceivable that microorganisms in saline soils are more tolerant to drying and rewetting (DRW) stress than those in
non-saline soils. An experiment was carried out with three different salinity levels: electrical conductivity (EC1:5) 0, 2 and 4 dS m?1 (EC0, EC2, EC4), and two water treatments: a constantly moist control or two DRW cycles. Respiration as an indicator of microbial
activity was measured throughout the 59 days of incubation. At the end of the second dry period (day 35) and at the end of
the following moist incubation (day 59), microbial biomass and microbial community structure were determined by phospholipid
fatty acid (PLFA) analysis. Increasing salinity decreased microbial activity but did not affect its resistance to DRW. On
day 59, cumulative respiration decreased in the order EC0 > EC2 > EC4 with no differences between water treatments. Fungal
biomass was negatively affected by salinity at the end of the experiment, while bacterial biomass was unaffected. Microbial
community structure in moist treatments differed between salinity levels, with EC4 influencing microbial community structure
earlier than EC2. The resistance of microbial communities to DRW stress was salt level dependent; only beyond a critical salinity
level adaptation to salt stress was able to reduce the impact of water stress on microbial community structure.
Content Type Journal Article
Pages 1-10
DOI 10.1007/s10533-011-9672-1
Authors
Karen Baumann, The Waite Research Institute, School of Agriculture, Food and Wine, The University of Adelaide, Adelaide, SA 5005, Australia
Petra Marschner, The Waite Research Institute, School of Agriculture, Food and Wine, The University of Adelaide, Adelaide, SA 5005, Australia
In the Sargasso Sea, maximum dimethylsulfide (DMS) accumulation occurs in summer, concomitant with the minimum of chlorophyll
and 2 months later than its precursor, dimethylsulfoniopropionate (DMSP). This phenomenon is often referred to as the DMS
“summer paradox”. It has been previously suggested that the main agent triggering this pattern is increasing irradiance leading
to light stress-induced DMS release from phytoplankton cells. We have developed a new model describing DMS(P) dynamics in
the water column and used it to investigate how and to what extent processes other than light induced DMS exudation from phytoplankton,
may contribute to the DMS summer paradox. To do this, we have conceptually divided the DMS “summer paradox” into two components:
(1) the temporal decoupling between chlorophyll and DMSP and (2) the temporal decoupling between DMSP and DMS. Our results
suggest that it is possible to explain the above cited patterns by means of two different dynamics, respectively: (1) a succession
of phytoplankton types in the surface water and (2) the bacterially mediated DMSP(d) to DMS conversion, seasonally varying
as a function of nutrient limitation. This work differs from previous modelling studies in that the presented model suggests
that phytoplankton light-stress induced processes may only partially explain the summer paradox, not being able to explain
the decoupling between DMSP and DMS, which is possibly the more challenging aspect of this phenomenon. Our study, therefore,
provides an “alternative” explanation to the summer paradox further underlining the major role that bacteria potentially play
in DMS production and fate.
Content Type Journal Article
Pages 1-13
DOI 10.1007/s10533-011-9674-z
Authors
Luca Polimene, Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
Stephen D. Archer, Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
Momme Butenschön, Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
J. Icarus Allen, Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
In 1959, Athol Rafter began a substantial programme of monitoring the flow of 14C produced by atmospheric thermonuclear tests through New Zealand’s atmosphere, biosphere and soil. By building on the original
measurements through ongoing sampling, a database of over 500 soil radiocarbon measurements spanning 50 years has now been
compiled. The datasets, including an 11-point time series, allow strong focus on the robust quantification of residence times
ranging from years to decades. We describe key aspects of the dataset, including the ability to identify critical assumptions
inherent in calculating soil C residence times. The 3 most critical assumptions relate to: (1) the proportion of old C (“fraction
passive”), (2) the lag time between photosynthesis and C entering the modeled pool, and (3) changes in the rates of C input
(i.e., steady state). We demonstrate the ability to compare residence times in contrasting sites, such Andisols and non-Andisols,
and the ability to calculate residence times across a range of soil depths. We use 14C in a two-box model to quantify soil carbon turnover parameters in deforested dairy pastures under similar climate in the
Tokomaru silt loam (non-Andisol) versus the Egmont black loam (Andisol), originally sampled in 1962, 1965 and 1969, and resampled
again in 2008. The 14C-based residence times of the main soil C pool in surface soil (~8 cm) are ~9 years in the Tokomaru soils compared to ~17 years
for the Egmont soils. This difference represents nearly a doubling of soil C residence time, and roughly explains the doubling
of the soil C stock. Passive soil C comprises 15% of the soil C pool in Tokomaru soils versus 27% in Egmont soils. A similar
difference in residence times is found in a second surface soil comparison between the Bruntwood soil (Andisol) and the Te
Kowhai soil (non-Andisol) with residence times of 18 and 27 years, respectively. The comparisons support evidence that C dynamics
do differ in Andisols versus non-Andisols, as a result of both the mineral allophane and Al complexation. Expanding our calculations
beyond surface soil, we show that thickening the calculation depth by combining horizons allows robust residence times to
be calculated at a range of depths. Overall, the large and systematically collected dataset demonstrate that soil C residence
times of the main soil C pool can be routinely calculated using 14C wherever samples collected 10 or more years apart in New Zealand grassland soils are available, and presumably under similar
circumstances in other soils worldwide.
Content Type Journal Article
Pages 1-9
DOI 10.1007/s10533-011-9675-y
Authors
W. Troy Baisden, National Isotope Centre, GNS Science, PO Box 31312, Lower Hutt, New Zealand
Roger L. Parfitt, Landcare Research, Private Bag 11052, Palmerston North, New Zealand
Craig Ross, Landcare Research, Private Bag 11052, Palmerston North, New Zealand
Louis A. Schipper, Earth and Ocean Sciences, University of Waikato, Waikato, New Zealand
Silvia Canessa, National Isotope Centre, GNS Science, PO Box 31312, Lower Hutt, New Zealand
Controls on chemical weathering, such as bedrock geology, runoff, and temperature, are considered to be the primary drivers
of Si transport from the continents to the oceans. However, recent work has highlighted terrestrial vegetation as an important
control over Si cycling. Here we show that at the regional scale (Southern New England, USA), land use/land cover (LULC) is
an important variable controlling the net transport of Si from the land to the sea, accounting for at least 40% of dissolved
Si (DSi) fluxes. A multiple linear regression model using average DSi fluxes from 25 rivers (>2,300 observations) shows the
percent forest cover, as well as development and agricultural land use, to be significant (p < 0.05) drivers of DSi flux. This was true regardless of watershed size and lithology. Furthermore, forest cover is significantly
negatively correlated, while development is significantly positively correlated, with Si concentrations and fluxes. We hypothesize
that these relationships are due to several mechanisms, specifically the ability of terrestrial vegetation to store large
amounts of Si within its biomass, the altered watershed hydrology that accompanies LULC change, and the capability of urban
regions to serve as sources of Si to aquatic systems. Thus, we conclude that anthropogenic activities may be directly perturbing
the global Si cycle through land use change and we offer a conceptual model which highlights a new approach to understanding
the non-geochemical controls on Si fluxes.
Content Type Journal Article
Pages 1-14
DOI 10.1007/s10533-011-9671-2
Authors
J. C. Carey, Department of Earth Sciences, Boston University, Boston, USA
R. W. Fulweiler, Department of Earth Sciences, Boston University, Boston, USA
About a decade of dimethylsulphide (DMS) measurements in the North East Pacific are summarized and compared to model simulations.
Bottle samples at various depths have been taken three times per year along Line P from the British Columbia coast to Ocean
Station Papa (145° W, 50° N). Despite the long timeseries, DMS measurements are still sparse and the data show large variabilities
in concentrations both spatially and temporally. DMS concentrations in late summer have been consistently high, while spring
measurements at the offshore stations suggest a downward trend over the past years. Low values in spring, however, have also
been recorded in the late 1990s, which might hint to interannual variability in the onset of the spring bloom and/or plankton
assemblage rather than to a response to recent climate change. Some of the variability, both short-term and interannual, can
be caused by regional or local preconditioning of the physical environment. The model simulations provide examples where periods
of low winds, shallow mixed layers and sometimes high irradiance follow a mixing event and cause DMS peaks on various time
scales as well as consistently elevated DMS concentrations for longer timeperiods. The model in its current configuration,
which has been calibrated with measurements in the late 1990s/early 2000s, is not able to capture the low values in winter
and spring observed in recent years. We suggest that this is due to missing or misrepresented links in the biogeochemical
parameterizations of the model, e.g., an incomplete representation of variations in the phytoplankton assemblage. Including
a seasonally varying S:N ratio to account for the absence of dinoflagellates in winter and spring significantly improves the
simulation. Variability in DMS concentrations can also be induced by natural iron fertilization, which the model reproduces
when timing is specified. For example, the model can reproduce the effects of natural volcanic Fe fertilization on surface
water plankton dynamics and mixed layer DMS accumulation. The model also shows that the amplitude of the short term variability
(days) increases when DMSP producing phytoplankton are less iron limited.
Content Type Journal Article
Pages 1-17
DOI 10.1007/s10533-011-9669-9
Authors
Nadja S. Steiner, Institute of Ocean Sciences, Fisheries and Oceans Canada, Sidney, BC, Canada
Marie Robert, Institute of Ocean Sciences, Fisheries and Oceans Canada, Sidney, BC, Canada
Michael Arychuk, Institute of Ocean Sciences, Fisheries and Oceans Canada, Sidney, BC, Canada
Maurice L. Levasseur, Department of Biology (Quebec Ocean), University Laval, Quebec, QC, Canada
Anissa Merzouk, University of British Columbia, Vancouver, BC, Canada
M. Angelica Peña, Institute of Ocean Sciences, Fisheries and Oceans Canada, Sidney, BC, Canada
Wendy A. Richardson, Institute of Ocean Sciences, Fisheries and Oceans Canada, Sidney, BC, Canada
Philippe D. Tortell, University of British Columbia, Vancouver, BC, Canada
The kinetics and elemental composition of cellular units that mediate production and respiration are the basis for the metabolic
and stoichiometric theories of ecological organization. This theoretical framework extends to the activities of microbial
enzymes released into the environment (ecoenzymes) that mediate the release of assimilable substrate from detrital organic
matter. In this paper, we analyze the stoichiometry of ecoenzymatic activities in the surface sediments of lotic ecosystems
and compare those results to the stoichiometry observed in terrestrial soils. We relate these ecoenzymatic ratios to energy
and nutrient availability in the environment as well as microbial elemental content and growth efficiency. The data, collected
by US Environmental Protection Agency, include the potential activities of 11 enzymes for 2,200 samples collected across the
US, along with analyses of sediment C, N and P content. On average, ecoenzymatic activities in stream sediments are 2–5 times
greater per gC than those of terrestrial soils. Ecoenzymatic ratios of C, N and P acquisition activities support elemental
analyses showing that microbial metabolism is more likely to be C-limited than N or P-limited compared to terrestrial soils.
Ratios of hydrolytic to oxidative activities indicate that sediment organic matter is more labile than soil organic matter
and N acquisition is less dependent on humic oxidation. The mean activity ratios of glycosidases and aminopeptidases reflect
the environmental abundance of their respective substrates. For both freshwater sediments and terrestrial soils, the mean
C:nutrient ratio of microbial biomass normalized to growth efficiency approximates the mean ecoenzymatic C:nutrient activity
ratios normalized to environmental C:nutrient abundance. This relationship defines a condition for biogeochemical equilibrium
consistent with stoichiometric and metabolic theory.
Content Type Journal Article
Pages 1-13
DOI 10.1007/s10533-011-9676-x
Authors
Robert L. Sinsabaugh, Biology Department, University of New Mexico, Albuquerque, NM 87131, USA
Jennifer J. Follstad Shah, Watershed Sciences Department, Utah State University, Logan, UT 84322, USA
Brian H. Hill, Mid-Continent Ecology Division, U.S. Environmental Protection Agency, Duluth, MN 55804, USA
Colleen M. Elonen, Mid-Continent Ecology Division, U.S. Environmental Protection Agency, Duluth, MN 55804, USA
A response to ‘Changes in water colour between 1986 and 2006 in the headwaters of the River Nidd, Yorkshire, UK: a critique of methodological approaches and measurement of burning management’ by Yallop et al
Content Type Journal Article
Pages 1-5
DOI 10.1007/s10533-011-9665-0
Authors
Pippa J. Chapman, water@leeds, School of Geography, University of Leeds, Leeds, LS2 9JT UK
Sheila M. Palmer, water@leeds, School of Geography, University of Leeds, Leeds, LS2 9JT UK
Brian J. Irvine, water@leeds, School of Geography, University of Leeds, Leeds, LS2 9JT UK
Gordon Mitchell, water@leeds, School of Geography, University of Leeds, Leeds, LS2 9JT UK
Adrian T. McDonald, water@leeds, School of Geography, University of Leeds, Leeds, LS2 9JT UK
The enzyme product of the dddD gene, found in several different marine bacteria, acts on dimethylsulfoniopropionate (DMSP), liberating dimethyl sulfide
(DMS) and generating 3-OH-propionate as the initially detected C3 product. In many bacteria, dddD is near genes whose sequence suggests that they encode a DMSP transporter. These are of two very different types, in the
BCCT (betaine-carnitine-choline transporter) family or resembling members of the ABC super-family that import betaines. Even
within these two families, the amino acid sequences of these putative transporters are not particularly similar to each other.
Genes for the predicted DMSP transporters of Halomonas and Marinomonas (both BCCT type) and of Burkholderia ambifaria AMMD (ABC-type) were each cloned and introduced into an Escherichia coli mutant (MKH13) that is defective in betaine uptake, and so fails to catabolise DMSP even when a cloned dddD gene was present, due to the failure of the substrate to be imported. DMSP-dependent DMS production (Ddd+ phenotype) was restored by introducing any of these cloned transporters into MKH13 containing dddD. Other marine bacteria use a range of enzymes, called DddL, DddP, DddQ, DddW and DddY, to cleave DMSP, but the various ddd genes that encode them are usually unlinked to any that are predicted to encode betaine transporters. We identified one gene
in Sulfitobacter sp. EE-36 and two in Roseovarius nubinhibens ISM, which, when cloned and introduced into E. coli MKH13, overcame its osmotic sensitivity when it was grown with DMSP or other exogenous betaines. These genes all encoded
BCCT transporters, but were unlinked to any known genes involved in DMSP catabolism in these two strains of ?-proteobacteria.
Content Type Journal Article
Pages 1-10
DOI 10.1007/s10533-011-9666-z
Authors
Lei Sun, School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ UK
Andrew R. J. Curson, School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ UK
Jonathan D. Todd, School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ UK
Andrew W. B. Johnston, School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ UK
Within the southeast Canada and northeast USA region, a peak in sulphate (SO42?) concentration has been reported for some streams following periods of substantial catchment drying during the summer months
(ON, Canada; VT, NH and NY, USA). However, it is currently unclear if a SO42? response to seasonal drying is widespread across the broader region, or to what extent the level of response varies among
catchments. In our study, SO42? response to seasonal drying was compared in 20 catchments from 11 locations across southeastern Canada (ON, QC and NS) and
northeastern USA (NH, NY, VT, WV and ME). Using long-term monitoring data of stream discharge and chemistry, the number of
days for each month of the dry season (# d) when discharge (Q) was below a threshold level (25th percentile; Q25) was calculated for each catchment to give a measure of ‘seasonal dryness’ (# d Q < Q25). A SO42? response score (rs) was then calculated for each catchment based on linear regression analysis of # d Q < Q25 versus either the annual SO42? concentration, or the residual of annual SO42? concentration as a function of time (year). The final rs values for each catchment provided an estimate of the proportion of variation in annual SO42? concentration which could be explained by seasonal drying (possible rs range = 0–1). Of the 20 catchments, 13 exhibited some level of a SO42? response to seasonal drying (rs = 0.04–0.72) with an additional two catchments exhibiting a SO42? response for one or more seasons. SO42? response scores were positively related to percent wetland area (w) (rs = 1.000 ? 0.978e?0.054*w, r2 = 0.44) and percent saturated area (sat) (rs = 0.481 ? 0.488e?0.101*sat, r2 = 0.54) indicating that wetlands/saturated areas were an important driver of regional variation in the SO42? response to seasonal drying. Our results suggest that any shift towards drier summers as a result of climate change could
impact SO42? dynamics in a large number of catchments throughout the region.
Content Type Journal Article
Pages 1-17
DOI 10.1007/s10533-011-9664-1
Authors
J. G. Kerr, Department of Geography, Trent University, Peterborough, ON K9J 7B8, Canada
M. C. Eimers, Department of Geography, Trent University, Peterborough, ON K9J 7B8, Canada
I. F. Creed, Department of Biology, University of Western Ontario, London, ON, Canada
M. B. Adams, USDA Forest Service, Parsons, WV, USA
F. Beall, Natural Resources Canada, Canadian Forest Service, Sault Ste. Marie, ON, Canada
D. Burns, US Geological Survey, Troy, NY, USA
J. L. Campbell, US Forest Service, Durham, NH, USA
S. F. Christopher, Virginia Water Resources Research Center, Virginia Tech, Blacksburg, VA, USA
T. A. Clair, Water Science and Technology Branch, Environment Canada, Sackville, NB, Canada
F. Courchesne, Département de Géographie, Université de Montréal, Montreal, QC, Canada
L. Duchesne, Forêt Québec, Ministère Des Ressources Naturelles, Québec, QC, Canada
I. Fernandez, Department of Plant, Soil, and Environmental Sciences, University of Maine, Orono, ME, USA
D. Houle, Ministère Des Ressources naturelles et de la Faune, Québec, QC, Canada
D. S. Jeffries, Aquatic Ecosystems Research Impacts Division, National Water Research Institute, Environment Canada, Burlington, ON, Canada
G. E. Likens, Cary Institute of Ecosystem Studies, Millbrook, NY, USA
M. J. Mitchell, College of Environmental Science and Forestry, SUNY, Syracuse, NY, USA
J. Shanley, US Geological Survey, Montpelier, VT, USA
H. Yao, Ontario Ministry of Environment, Dorset, ON, Canada
Soil nitrogen (N) is an important component in maintaining ecosystem stability, and the introduction of non-native plants
can alter N cycling by changing litter quality and quantity, nutrient uptake patterns, and soil food webs. Our goal was to
determine the effects of Bromus tectorum (C3) invasion on soil microbial N cycling in adjacent non-invaded and invaded C3 and C4 native arid grasslands. We monitored resin-extractable N, plant and soil ?13C and ?15N, gross rates of inorganic N mineralization and consumption, and the quantity and isotopic composition of microbial phospholipid
biomarkers. In invaded C3 communities, labile soil organic N and gross and net rates of soil N transformations increased, indicating an increase in
overall microbial N cycling. In invaded C4 communities labile soil N stayed constant, but gross N flux rates increased. The ?13C of phospholipid biomarkers in invaded C4 communities showed that some portion of the soil bacterial population preferentially decomposed invader C3-derived litter over that from the native C4 species. Invasion in C4 grasslands also significantly decreased the proportion of fungal to bacterial phospholipid biomarkers. Different processes
are occurring in response to B. tectorum invasion in each of these two native grasslands that: 1) alter the size of soil N pools, and/or 2) the activity of the microbial
community. Both processes provide mechanisms for altering long-term N dynamics in these ecosystems and highlight how multiple
mechanisms can lead to similar effects on ecosystem function, which may be important for the construction of future biogeochemical
process models.
Content Type Journal Article
Pages 1-15
DOI 10.1007/s10533-011-9668-x
Authors
Sean M. Schaeffer, School of Biological Sciences and Laboratory for Biotechnology and Bioanalysis Stable Isotope Core, Washington State University, Pullman, WA 99164-4236, USA
Susan E. Ziegler, Department of Earth Sciences, Memorial University, St. John’s, NL A1B 3X5, Canada
Jayne Belnap, Biological Resources Division, United States Geological Survey, 2290 S Resource Boulevard, Moab, UT 84532, USA
R. D. Evans, School of Biological Sciences and Laboratory for Biotechnology and Bioanalysis Stable Isotope Core, Washington State University, Pullman, WA 99164-4236, USA
Soil heterotrophic respiration fluxes at field scale may exhibit a substantial spatial variability. The aim of this study
was (1) to elucidate the role of soil temperature and different carbon fractions on heterotrophic soil respiration and (2)
to test by which of three different statistical approaches (multiple regression, external drift kriging and simulated annealing)
such influences may be best represented. Chamber-based measurements of respiration fluxes were carried out within a 180 × 40 m
bare soil plot. Soil temperature was measured simultaneously to the flux measurements. Further, we recorded total soil organic
carbon content, apparent electrical conductivity as well as mid-infrared spectroscopy-based carbon fractions as co-variates
in addition to basic soil properties like stone content and texture. A stepwise multiple linear regression procedure was used
to spatially predict bare soil respiration from the co-variates. The results showed that the particulate organic matter (POM)
fraction and terrain elevation were able to explain the spatial pattern of heterotrophic soil respiration (R2 = 0.45). In a second step we applied external drift kriging to determine the improvement of using co-variates in an estimation
procedure in comparison to ordinary kriging. The maximum relative improvement using the co-variates in terms of the root mean
square error was 16%. In a third step we applied simulated annealing to perform stochastic simulations conditioned with external
drift kriging to generate more realistic spatial patterns of heterotrophic respiration at plot scale. The conditional stochastic
simulations revealed a significantly improved reproduction of the probability density function, the G-statistics value increased
from 0.36 to 0.92. Further, the error in the reproduction of the semivariogram of the original point data decreased by more
than one order of magnitude. All this confirmed that the mapping of soil respiration patterns may be significantly improved
when considering terrain elevation and spatial heterogeneity of POM in combination with a conditional stochastic simulation.
Content Type Journal Article
Pages 1-16
DOI 10.1007/s10533-011-9661-4
Authors
M. Herbst, Agrosphere Institute, IBG-3, Forschungszentrum Jülich GmbH, Jülich, Germany
L. Bornemann, Institute of Crop Science and Resource Conservation—Soil Science, Bonn, Germany
A. Graf, Agrosphere Institute, IBG-3, Forschungszentrum Jülich GmbH, Jülich, Germany
G. Welp, Institute of Crop Science and Resource Conservation—Soil Science, Bonn, Germany
H. Vereecken, Agrosphere Institute, IBG-3, Forschungszentrum Jülich GmbH, Jülich, Germany
W. Amelung, Institute of Crop Science and Resource Conservation—Soil Science, Bonn, Germany
Wildfire in California annual grasslands is an important ecological disturbance and ecosystem control. Regional and global
climate changes that affect aboveground biomass will alter fire-related nutrient loading and promote increased frequency and
severity of fire in these systems. This can have long-term impacts on soil microbial dynamics and nutrient cycling, particularly
in N-limited systems such as annual grasslands. We examined the effects of a low-severity fire on microbial biomass and specific
microbial lipid biomarkers over 3 years following a fire at the Jasper Ridge Global Change Experiment. We also examined the
impact of fire on the abundance of ammonia-oxidizing bacteria (AOB), specifically Nitrosospira Cluster 3a ammonia-oxidizers, and nitrification rates 9 months post-fire. Finally, we examined the interactive effects of
fire and three other global change factors (N-deposition, precipitation and CO2) on plant biomass and soil microbial communities for three growing seasons after fire. Our results indicate that a low-severity
fire is associated with earlier season primary productivity and higher soil-NH4+ concentrations in the first growing season following fire. Belowground productivity and total microbial biomass were not
influenced by fire. Diagnostic microbial lipid biomarkers, including those for Gram-positive bacteria and Gram-negative bacteria,
were reduced by fire 9- and 21-months post-fire, respectively. All effects of fire were indiscernible by 33-months post-fire,
suggesting that above and belowground responses to fire do not persist in the long-term and that these grassland communities
are resilient to fire disturbance. While N-deposition increased soil NH4+, and thus available NH3, AOB abundance, nitrification rates and Cluster 3a AOB, similar increases in NH3 in the fire plots did not affect AOB or nitrification. We hypothesize that this difference in response to N-addition involves
a mediation of P-limitation as a result of fire, possibly enhanced by increased plant competition and arbuscular mycorrhizal
fungi–plant associations after fire.
Content Type Journal Article
Pages 1-21
DOI 10.1007/s10533-011-9654-3
Authors
Kathryn M. Docherty, Department of Biological Sciences, Western Michigan University, 1903 West Michigan Ave., Kalamazoo, MI 49008-5410, USA
Teri C. Balser, Department of Soil Science, University of Wisconsin-Madison, 1525 Observatory Drive, Madison, WI 53706, USA
Brendan J. M. Bohannan, Center for Ecology and Evolutionary Biology (CEEB), University of Oregon, P.O. Box 5289, Eugene, OR 97403, USA
Jessica L. M. Gutknecht, Department of Soil Science, University of Wisconsin-Madison, 1525 Observatory Drive, Madison, WI 53706, USA
Proper management of soil organic matter (SOM) is needed for maintaining soil fertility and for mitigation of the global increase
in atmospheric CO2 concentrations and should be informed by knowledge about the sources, spatial organisation and stabilisation processes of
SOM. Recently, microbial biomass residues (i.e. necromass) have been identified as a significant source of SOM. Here, we propose
that cell wall envelopes of bacteria and fungi are stabilised in soil and contribute significantly to small-particulate SOM
formation. This hypothesis is based on the mass balance of a soil incubation experiment with 13C-labelled bacterial cells and on the visualisation of the microbial residues by means of scanning electron microscopy (SEM).
At the end of a 224-day incubation, 50% of the biomass-derived C remained in the soil, mainly in the non-living part of SOM
(40% of the added biomass C). SEM micrographs only rarely showed intact cells. Instead, organic patchy fragments of 200–500 nm
size were abundant and these fragments were associated with all stages of cell envelope decay and fragmentation. Similar fragments,
developed on initially clean and sterile in situ microcosms during exposure to groundwater, provide clear evidence for their
formation during microbial growth and surface colonisation. Microbial cell envelope fragments thus contribute significantly
to SOM formation. This origin and the related macromolecular architecture of SOM are consistent with most observations on
SOM, including the abundance of microbial-derived biomarkers, the low C/N ratio, the water repellency and the stabilisation
of biomolecules, which in theory should be easily degradable.
Content Type Journal Article
Category Synthesis and Emerging Ideas
Pages 1-15
DOI 10.1007/s10533-011-9658-z
Authors
Anja Miltner, UFZ – Helmholtz-Centre for Environmental Research, Department of Environmental Biotechnology, Permoserstr. 15, 04318 Leipzig, Germany
Petra Bombach, UFZ – Helmholtz-Centre for Environmental Research, Department of Isotope Biogeochemistry, Permoserstr. 15, 04318 Leipzig, Germany
Burkhard Schmidt-Brücken, Institute of Material Science, Technische Universität Dresden, Hallwachsstr. 3, 01069 Dresden, Germany
Matthias Kästner, UFZ – Helmholtz-Centre for Environmental Research, Department of Environmental Biotechnology, Permoserstr. 15, 04318 Leipzig, Germany
The marine ?-proteobacterium Oceanimonas doudoroffii was shown to have at least three different enzymes, each of which can cleave dimethylsulfoniopropionate (DMSP), an abundant
compatible solute made by different classes of marine phytoplankton. These various DMSP lyases have similarities, but also
some differences to those that had been identified in other bacteria. This was demonstrated by cloning each of the corresponding
genes and transferring them into other species of bacteria in which backgrounds they conferred the ability to catabolise DMSP,
releasing dimethyl sulfide (DMS) as one of the products (Ddd+ phenotype; DMSP-dependent DMS). One of these genes resembled dddD, which was in a cluster with other ddd genes variously involved in subsequent steps of DMSP catabolism, in DMSP import and in DMSP-dependent transcriptional regulation.
The other two gene products both had sequence similarity to the previously identified DddP lyase. However, these two Oceanimonas DddP polypeptides were not particularly similar to each other and were in two different sub-branches compared to those that
had been studied in strains of the Roseobacter clade of bacteria. One of these O. doudoroffii enzymes, DddP1, most closely resembled gene products in a disparate group of microbes that included two bacteria, Vibrio orientalis and Puniceispirillum marinum and, more strikingly, some Ascomycete fungi that can catabolise DMSP. Previously, the only bacteria known to have multiple
ways to catabolise DMSP were in the Roseobacter clade, which were also the only bacteria that had been shown to have functional
DddP DMSP lyases. Thus Oceanimonas doudoroffii is unusual on more than one count and likely acquired its dddD, dddP1 and dddP2 genes by independent horizontal gene transfer events.
Content Type Journal Article
Pages 1-11
DOI 10.1007/s10533-011-9663-2
Authors
Andrew R. J. Curson, School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ UK
Emily K. Fowler, School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ UK
Shilo Dickens, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1GA UK
Andrew W. B. Johnston, School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ UK
Jonathan D. Todd, School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ UK
Global environmental changes are expected to alter ecosystem carbon and nitrogen cycling, but the interactive effects of multiple
simultaneous environmental changes are poorly understood. Effects of these changes on the production of nitrous oxide (N2O), an important greenhouse gas, could accelerate climate change. We assessed the responses of soil N2O fluxes to elevated CO2, heat, altered precipitation, and enhanced nitrogen deposition, as well as their interactions, in an annual grassland at
the Jasper Ridge Global Change Experiment (CA, USA). Measurements were conducted after 6, 7 and 8 years of treatments. Elevated
precipitation increased N2O efflux, especially in combination with added nitrogen and heat. Path analysis supported the idea that increased denitrification
due to increased soil water content and higher labile carbon availability best explained increased N2O efflux, with a smaller, indirect contribution from nitrification. In our data and across the literature, single-factor responses
tended to overestimate interactive responses, except when global change was combined with disturbance by fire, in which case
interactive effects were large. Thus, for chronic global environmental changes, higher order interactions dampened responses
of N2O efflux to multiple global environmental changes, but interactions were strongly positive when global change was combined
with disturbance. Testing whether these responses are general should be a high priority for future research.
Content Type Journal Article
Pages 1-16
DOI 10.1007/s10533-011-9655-2
Authors
Jamie R. Brown, Department of Biological Sciences and Merriam-Powell Center for Environmental Research, Northern Arizona University, Flagstaff, AZ 86011, USA
Joseph C. Blankinship, Department of Biological Sciences and Merriam-Powell Center for Environmental Research, Northern Arizona University, Flagstaff, AZ 86011, USA
Audrey Niboyet, Laboratoire Ecologie, Systématique et Evolution, UMR 8079 Université Paris-Sud 11/CNRS/AgroParisTech, Université Paris-Sud 11, 91405 Orsay, France
Kees Jan van Groenigen, Department of Biological Sciences and Merriam-Powell Center for Environmental Research, Northern Arizona University, Flagstaff, AZ 86011, USA
Paul Dijkstra, Department of Biological Sciences and Merriam-Powell Center for Environmental Research, Northern Arizona University, Flagstaff, AZ 86011, USA
Xavier Le Roux, Laboratoire d’Ecologie Microbienne, Université de Lyon, Université Lyon 1, UMR CNRS 5557, USC INRA 1193, 43 boulevard du 11 novembre 1918, 69622 Villeurbanne, France
Paul W. Leadley, Laboratoire Ecologie, Systématique et Evolution, Université Paris-Sud, UMR 8079 Université Paris-Sud/CNRS/AgroParisTech, 91405 Orsay, France
Bruce A. Hungate, Department of Biological Sciences and Merriam-Powell Center for Environmental Research, Northern Arizona University, Flagstaff, AZ 86011, USA
Organic matter (OM) in loess-paleosol sequences is used for paleoenvironmental reconstructions, based e.g. on stable carbon
isotope composition. Loess OM (LOM) is assumed to derive from synsedimentary vegetation, i.e. predominantly grass. However,
low organic C contents make LOM prone to postsedimentary contamination. It was the aim of this study to reveal (1) whether
OM of the loess sequence at Nussloch (SW Germany) was altered by postsedimentary input, (2) to which depth, and (3) from which
source vegetation this younger OM derives. Therefore, the alkane composition of LOM was compared to that of potential source
OM for postsedimentary contamination: recent soil, vegetation growing on the loess sequence, calcified roots (rhizoliths)
which derive from postsedimentary deep-rooting plants but not from recent vegetation, and loess in direct vicinity of these
former roots. Alkane molecular proxies including carbon preference index and average chain length revealed that grass biomass
was the source of soil and LOM. The latter was, except for the uppermost 0.6 m of loess, not affected by pedogenic processes.
Further, recent vegetation did not contribute to OM within and loess adjacent to rhizoliths, which were formed under native
tree and/or shrub vegetation prior to agricultural use. Strongest degradation of LOM and large amounts of microbial derived
OM were found in rhizoloess, indicating former rhizosphere processes. Molecular proxies indicate that overprinting of LOM
even in loess distant to former roots cannot be excluded. Therefore, paleoenvironmental reconstructions based on loess ?13Corg should be regarded with caution.
Content Type Journal Article
Pages 1-18
DOI 10.1007/s10533-011-9659-y
Authors
Martina Gocke, Department of Agroecosystem Research, BayCEER, University of Bayreuth, 95447 Bayreuth, Germany
Yakov Kuzyakov, Department of Soil Science of Temperate and Boreal Ecosystems, University of Göttingen, 37077 Göttingen, Germany
Guido L. B. Wiesenberg, Department of Agroecosystem Research, BayCEER, University of Bayreuth, 95447 Bayreuth, Germany
The global surface seawater dimethylsulphide (DMS) database (http://saga.pmel.noaa.gov/dms/) contains >50,000 data points and is the second largest trace gas database after carbon dioxide. However, there has been
relatively little quality control on the data that have been collated to date. Furthermore, the recent development of technologies
capable of high frequency (>1 Hz) DMS measurements will have a disproportionate effect on the database in future years. At
this juncture, the comparability of analytical techniques, sample handling methodologies and standards are pressing issues
that the DMS community needs to address. In October 2010, during the Fifth International Symposium on Biological and Environmental
Chemistry of DMS(P) and Related Compounds held in Goa, India, attendees participated in a discussion concerning the current
DMS database and its future development. We develop some of the ideas from that session and combine them with available data.
From the few inter-comparison exercises that have been conducted we show that variability between existing measurements within
the DMS database is likely to be ?25%. Tests comparing different DMSP·HCl standards demonstrate that a reference calibration
standard would be beneficial for the DMS community. Confidence in future data collation would be substantially improved with
a comprehensive inter-comparison experiment between new analytical techniques and sampling methodologies (e.g., mass spectrometers
with equilibrators attached to a continuous flow of seawater) and more established methods (i.e., filtered samples analysed
with purge and trap gas chromatography). We conclude with recommendations for the future expansion of the DMS database and
its data quality control.
Content Type Journal Article
Pages 1-15
DOI 10.1007/s10533-011-9662-3
Authors
T. G. Bell, Laboratory for Global Marine and Atmospheric Chemistry (LGMAC), School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ UK
G. Malin, Laboratory for Global Marine and Atmospheric Chemistry (LGMAC), School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ UK
G. A. Lee, Laboratory for Global Marine and Atmospheric Chemistry (LGMAC), School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ UK
J. Stefels, Laboratory of Plant Physiology, Centre for Ecological and Evolutionary Studies (CEES), University of Groningen, P.O. Box 11103, 9700 CC Groningen, The Netherlands
S. Archer, Plymouth Marine Laboratory, Plymouth, PL1 3DH UK
M. Steinke, Department of Biological Sciences, University of Essex, Colchester, CO4 3SQ UK
P. Matrai, Bigelow Laboratory for Ocean Sciences, 180 McKown Point, W. Boothbay Harbor, ME 04575-475, USA
Over the past three decades, Narragansett Bay has undergone various ecological changes, including significant decreases in
water column chlorophyll a concentrations, benthic oxygen uptake, and benthic nutrient regeneration rates. To add to this portrait of change, we measured
the net flux of N2 across the sediment–water interface over an annual cycle using the N2/Ar technique at seven sites in the bay for comparison with measurements made decades ago. Net denitrification rates ranged
from about 10–90 ?mol N2–N m?2 h?1 over the year. Denitrification rates were not significantly different among sites and had no clear correlation with temperature.
Net nitrogen fixation (?5 to ?650 ?mol N2–N m?2 h?1) was measured at three sites and only observed in summer (June–August). Neither denitrification nor nitrogen fixation exhibited
a consistent relationship with sediment oxygen demand or with fluxes of nitrite, nitrate, ammonium, total dissolved inorganic
nitrogen, or dissolved inorganic phosphate across all stations. In contrast to the mid-bay historical site where denitrification
rates have declined, denitrification rates in the Providence River Estuary have not changed significantly over the past 30 years.
Content Type Journal Article
Pages 1-14
DOI 10.1007/s10533-011-9660-5
Authors
Robinson W. Fulweiler, Earth Sciences Department, Boston University, Boston, MA 02215, USA
Scott W. Nixon, Graduate School of Oceanography, University of Rhode Island, Narragansett, 02882-1197 USA
The Angora Fire (summer of 2007) was the largest and most severe wildfire in recent history within the Lake Tahoe basin of
the Sierra Nevada. To determine the watershed response and to assess the potential for downstream impacts of nutrient and
sediment delivery to Lake Tahoe, we monitored the post-fire hydrology and stream water chemistry for 2 years at four locations
along the length of Angora Creek, a perennial stream draining the burned watershed. When compared with unburned streams, the
hydrology of Angora Creek indicated an earlier and faster melting of the spring snowpack. Peak stream water concentrations
of total N (TN) and ammonium occurred within the burned area, whereas peak concentrations of nitrate (NO3?), total P, soluble reactive P, total suspended solids, turbidity, electrical conductivity (EC), and dissolved organic C occurred
below the burned area. In comparison to pre-fire data, TN, NO3?, TP, total dissolved P, EC, and turbidity increased following the fire, particularly in the wetter second year. Yields for
subwatershed areas suggest that the burned urban subwatershed was the largest source of nutrients and sediments, whereas the
wet meadow subwatershed downstream of the burned area retained materials. Erosion control efforts, below-average annual precipitation
and the timing of its arrival (absence of summer and fall rainstorms), and the existence of a wet meadow below the burned
watershed likely reduced the negative impacts that would have been expected from such a severe wildfire.
Content Type Journal Article
Pages 1-16
DOI 10.1007/s10533-011-9657-0
Authors
Allison A. Oliver, Department of Land, Air, and Water Resources, University of California, Davis, CA 95616, USA
John E. Reuter, Department of Environmental Science & Policy and Tahoe Environmental Research Center, University of California, Davis, CA 95616, USA
Alan C. Heyvaert, Division of Hydrologic Sciences, Desert Research Institute, Reno, NV 89512, USA
Randy A. Dahlgren, Department of Land, Air, and Water Resources, University of California, Davis, CA 95616, USA
Strong correlations of soil total organic carbon (OC) with iron and aluminum phases reported frequently make it important
to quantify these organic matter (OM) associations, but selective extractants sometimes contain OC. Soil nitrogen is often
predominantly organic and might serve as a proxy for OM. We therefore investigated nitrogen associations with Fe and Al using
several selective extractants that use reductive, complexation, and alkaline approaches. Total dissolved nitrogen (TDN) correlated
strongly with extracted Fe and Al across seventeen samples, including highly- and weakly-weathered soils, iron-rich ultrabasic
soils, podzolic, and volcanic soils. Typically a quarter to a third of total soil nitrogen was dissolved by the various extractions,
though higher fractions (up to 60%) were found in spodic-horizon and volcanic surface-horizon samples. Similar proportions
were found for OC, using three OC-free extractants, indicating that TDN provides a useful surrogate for assessing OM partitioning
via extractants that contain OC. Use of TDN:metal ratios in extractant solutions allows estimation of extracted OM that could
have been sorptively associated with metal oxide/hydroxides and poorly-crystalline aluminosilicates. These ratios were often
high in extractions targeted at these adsorbents, and imply that usually most of the extracted TDN consists instead of organo–metal
complexes. The dynamics of these complexes may have stronger control on accumulation/remobilization of soil OM than those
of metal oxyhydroxides and poorly-crystalline aluminosilicates.
Content Type Journal Article
Pages 1-15
DOI 10.1007/s10533-011-9652-5
Authors
Rota Wagai, National Institute for Agro-Environmental Sciences, Carbon and Nutrient Cycling Division, 3-1-3, Kannondai, Tsukuba, Ibaraki 305-8604, Japan
Lawrence M. Mayer, School of Marine Sciences, University of Maine, Walpole, ME 04573, USA
Kanehiro Kitayama, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
Yasuhito Shirato, National Institute for Agro-Environmental Sciences, Natural Resources Inventory Center, 3-1-3, Kannondai, Tsukuba, Ibaraki 305-8604, Japan
Carbon dioxide (CO2) emissions were measured over a period of 3 years at the sub-alpine Swiss CARBOMONT site Rigi Seebodenalp. Here we show,
that winter respiration contributes larger than expected to the annual CO2 budget at this high altitude, rich in belowground organic carbon grassland (7–15% C by mass). Furthermore the contribution
of winter emissions to the annual CO2 budget is highly dependent on the definition of “winter” itself. Cumulative winter respiration determined over a 6 month
period from 15th of October until 15th of April contributed 23.3 ± 2.4 and 6.0 ± 0.3% to the annual respiration during the
years under observation, respectively. The insulation effect of snow and a lowering of the freezing point caused by high concentrations
of soil organic solutes prevented the soil from freezing. These conditions favored higher soil temperatures resulting in relatively
high respiratory losses. The duration of snow cover and micrometeorological conditions determining the photosynthetic activity
of the vegetation during snow-free periods influenced the size and the variability of the winter CO2 fluxes. Seasonal values are strongly influenced by the days at the end and the beginning of the defined winter period, caused
by large variations in length of periods with air temperatures below freezing. Losses of CO2 from the snow-covered soil were highest in winter 2003/2004. These high losses were partially explained by higher temperatures
in the topsoil, caused by higher air temperatures just before snowfall. Thus, losses are not a consequence of higher soil
temperatures registered during the summer heat wave 2003. However, water stress in summer 2003 might have caused an increment
in dead organic matter in the soil providing additional substrate for microbial respiration in the following winter. Although
considerable day-to-day fluctuations in snow effluxes were recorded, no conclusive and generally valid relationship could
be found between CO2 losses from the snow pack and snow depth, rate of snow melt, wind speed or air pressure. This suggests that time lags and
hysteresis effects may be more important for understanding winter respiration than concurrent environmental conditions in
most ecosystems of comparable type.
Content Type Journal Article
Pages 1-16
DOI 10.1007/s10533-011-9647-2
Authors
Lutz Merbold, Grassland Sciences Group, Institute of Agricultural Sciences, ETH Zurich, ETH Center LFW C55.2, 8092 Zurich, Switzerland
Nele Rogiers, Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
Werner Eugster, Grassland Sciences Group, Institute of Agricultural Sciences, ETH Zurich, ETH Center LFW C55.2, 8092 Zurich, Switzerland
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