TY  - JOUR
AB  - Life in hyperarid regions has adapted to extreme water scarcity through mechanisms like salt deliquescence. While halite (NaCl) crusts have been intensively studied and identified as one of the last habitats under hyperarid conditions, other less common hygroscopic salt crusts remain unexplored. Here, we investigated newly discovered deliquescent soil surfaces in the Atacama Desert, containing substantial amounts of nitrates, to evaluate their habitability for microorganisms. We characterized the environment with respect to water availability and biogeochemistry. Microbial abundances and composition were determined by cell cultivation experiments, 16S rRNA gene sequencing, and membrane phospholipid fatty acid (PLFA) analysis, while microbial activity was assessed by analyzing adenosine triphosphate (ATP) and the molecular composition of organic matter. Our findings reveal that, while the studied hygroscopic salts provide temporary water, microbial abundances and activity are lower in the studied soil surfaces than in non-deliquescent soil surfaces. Intriguingly, the deliquescent crusts are enriched in geochemically degraded organic matter, indicated by the molecular composition. We conclude that high nitrate concentrations in the hyperarid soils suppress microbial activity but preserve eolian-derived biomolecules. These insights are important for assessing the habitability and searching for life in hyperarid environments on Earth and beyond.
AU  - Arens, F.L.*
AU  - Airo, A.*
AU  - Sager, C.*
AU  - Grossart, H.P.*
AU  - Mangelsdorf, K.*
AU  - Meckenstock, R.U.*
AU  - Pannekens, M.*
AU  - Schmitt-Kopplin, P.
AU  - Uhl, J.
AU  - Valenzuela, B.*
AU  - Zamorano, P.*
AU  - Zoccarato, L.*
AU  - Schulze-Makuch, D.*
C1  - 72653
C2  - 56690
CY  - Bahnhofsallee 1e, Gottingen, 37081, Germany
SP  - 5305-5320
TI  - Microbial response to deliquescence of nitrate-rich soils in the hyperarid Atacama Desert.
JO  - Biogeosciences
VL  - 21
IS  - 22
PB  - Copernicus Gesellschaft Mbh
PY  - 2024
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - Heterotrophic CO2 fixation is a significant yet underappreciated CO2 flux in environmental carbon cycling. In contrast to photosynthesis and chemolithoautotrophy - the main recognized autotrophic CO2 fixation pathways - the importance of heterotrophic CO2 fixation remains enigmatic. All heterotrophs - from microorganisms to humans - take up CO2 and incorporate it into their biomass. Depending on the availability and quality of growth substrates, and drivers such as the CO2 partial pressure, heterotrophic CO2 fixation contributes at least 1%-5% and in the case of methanotrophs up to 50% of the carbon biomass. Assuming a standing stock of global heterotrophic biomass of 47-85PgC, we roughly estimate that up to 5PgC might be derived from heterotrophic CO2 fixation, and up to 12PgCyr-1 originating from heterotrophic CO2 fixation is funneled into the global annual heterotrophic production of 34-245PgCyr-1. These first estimates on the importance of heterotrophic fixation of inorganic carbon indicate that this pathway should be incorporated in present and future carbon cycling budgets.
AU  - Braun, A.
AU  - Spona-Friedl, M.
AU  - Avramov, M.
AU  - Elsner, M.
AU  - Baltar, F.*
AU  - Reinthaler, T.*
AU  - Herndl, G.J.*
AU  - Griebler, C.
C1  - 62375
C2  - 50696
CY  - Bahnhofsallee 1e, Gottingen, 37081, Germany
SP  - 3689-3700
TI  - Reviews and syntheses: Heterotrophic fixation of inorganic carbon - Significant but invisible flux in environmental carbon cycling.
JO  - Biogeosciences
VL  - 18
IS  - 12
PB  - Copernicus Gesellschaft Mbh
PY  - 2021
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - The hydrogen isotope composition of leaf-wax-derived biomarkers, e.g., long-chain n-alkanes (delta H-2(n-alkane)), is widely applied in paleoclimate. However, a direct reconstruction of the isotope composition of source water based on delta H-2(n-alkane) alone is challenging due to the enrichment of heavy isotopes during evaporation. The coupling of delta H-2(n-alkane) with delta O-18 of hemicellulose-derived sugars (delta O-18(sugar)) has the potential to disentangle this limitation and additionally to allow relative humidity reconstructions. Here, we present delta H-2(n-alkane) as well as delta O-18(sugar) results obtained from leaves of Eucalyptus globulus, Vicia faba, and Brassica oleracea, which grew under controlled conditions. We addressed the questions of (i) whether delta H-2(n-alkane) and delta O-18(sugar) values allow reconstructions of leaf water isotope composition, (ii) how accurately the reconstructed leaf water isotope composition enables relative humidity (RH) reconstruction, and (iii) whether the coupling of delta H-2(n-alkane) and delta O-18(sugar) enables a robust source water calculation. For all investigated species, the n-alkane n-C-29 was most abundant and therefore used for compound-specific delta H-2 measurements. For Vicia faba, additionally the delta H-2 values of n-C-31 could be evaluated robustly. Regarding hemicellulose-derived monosaccharides, arabinose and xylose were most abundant, and their delta O-18 values were therefore used to calculate weighted mean leaf delta O-18(sugar) values.Both delta H-2(n-alkane) and delta O-18(sugar) yielded significant correlations with delta H-2(leaf water) and delta O-18(leaf water), respectively (r(2)=0.45 and 0.85, respectively; p<0.001, n=24). Mean fractionation factors between biomarkers and leaf water were found to be -156 parts per thousand (ranging from -133 parts per thousand to -192 parts per thousand) for epsilon(n-alkane/leaf water) and +27.3 parts per thousand (ranging from +23.0 parts per thousand to 32.3 parts per thousand) for epsilon(sugar/leaf water), respectively. Modeled RHair values from a Craig-Gordon model using measured Tair, delta 2Hleaf water and delta 18Oleaf water as input correlate highly significantly with modeled RHair values (R2=0.84, p<0.001, RMSE = 6 %). When coupling delta H-2(n-alkane) and delta O-18(sugar) values, the correlation of modeled RHair values with measured RHair values is weaker but still highly significant, with R-2=0.54 (p<0.001, RMSE = 10 %). Finally, the reconstructed source water isotope composition (delta H-2(s) and delta O-18(s)) as calculated from our coupled approach matches the source water in the climate chamber experiment (delta H-2(tank water) and delta O-18(tank water)). This highlights the great potential of the coupled delta H-2(n-alkane)-delta O-18(sugar) paleohygrometer approach for paleoclimate and relative humidity reconstructions.
AU  - Hepp, J.*
AU  - Mayr. C.*
AU  - Rozanski, K.*
AU  - Schaefer, I.K.*
AU  - Tuthorn, M.*
AU  - Glaser, B.*
AU  - Juchelka, D.*
AU  - Stichler, W.
AU  - Zech, R.*
AU  - Zech, M.*
C1  - 63227
C2  - 51236
CY  - Bahnhofsallee 1e, Gottingen, 37081, Germany
SP  - 5363-5380
TI  - Validation of a coupled δ2Hn-alkane–δ18Osugarpaleohygrometer approach based on a climate chamber experiment.
JO  - Biogeosciences
VL  - 18
IS  - 19
PB  - Copernicus Gesellschaft Mbh
PY  - 2021
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - Nutrient leaching in intensively managed oil palm plantations can diminish soil fertility and water quality. There is a need to reduce this environmental footprint without sacrificing yield. In a large-scale oil palm plantation in Acrisol soil, we quantified nutrient leaching using a full factorial experiment with two fertilization rates (260 kg N, 50 kg P, and 220 kgKha1 yr1 as conventional practice and 136 kg N, 17 kg P, and 187 kgKha1 yr1, equal to harvest export, as reduced management) and two weeding methods (conventional herbicide application and mechanical weeding as reduced management) replicated in four blocks. Over the course of 1 year, we collected monthly soil pore water at 1.5m depth in three distinct management zones: palm circle, inter-row, and frond-stacked area. Nutrient leaching in the palm circle was low due to low solute concentrations and small drainage fluxes, probably resulting from large plant uptake. In contrast, nitrate and aluminum leaching losses were high in the inter-row due to the high concentrations and large drainage fluxes, possibly resulting from low plant uptake and low pH. In the frond-stacked area, base cation leaching was high, presumably from frond litter decomposition, but N leaching was low. Mechanical weeding reduced leaching losses of base cations compared to the conventional herbicide weeding probably because herbicides decreased ground vegetation and thus reduced soil nutrient retention. Reduced fertilization rates diminished the nitrate leaching losses. Leaching of total nitrogen in the mechanical weeding with reduced fertilization treatment (32 6 kgNha1 yr1) was less than half of the conventional management (74_20 kgNha1 yr1), whereas yields were not affected by these treatments. Our findings suggest that mechanical weeding and reduced fertilization should be included in the program by the Indonesian Ministry of Agriculture for precision farming (e.g., variable rates with plantation age), particularly for large-scale oil palm plantations.We further suggest including mechanical weeding and reduced fertilization in science-based policy recommendations, such as those endorsed by the Roundtable for Sustainable Palm Oil association.
AU  - Formaglio, G.*
AU  - Veldkamp, E.*
AU  - Duan, X.
AU  - Tjoa, A.*
AU  - Corre, M.D.*
C1  - 60533
C2  - 49330
CY  - Bahnhofsallee 1e, Gottingen, 37081, Germany
SP  - 5243-5262
TI  - Herbicide weed control increases nutrient leaching compared to mechanical weeding in a large-scale oil palm plantation.
JO  - Biogeosciences
VL  - 17
IS  - 21
PB  - Copernicus Gesellschaft Mbh
PY  - 2020
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - Permafrost-affected soils of the Arctic account for 70% or 727 Pg of the soil organic carbon (C) stored in the northern circumpolar permafrost region and therefore play a major role in the global C cycle. Most studies on the budgeting of C storage and the quality of soil organic matter (OM; SOM) in the northern circumpolar region focus on bulk soils. Thus, although there is a plethora of assumptions regarding differences in terms of C turnover or stability, little knowledge is available on the mechanisms stabilizing organic C in Arctic soils besides impaired decomposition due to low temperatures. To gain such knowledge, we investigated soils from Samoylov Island in the Lena River delta with respect to the composition and distribution of organic C among differently stabilized SOM fractions. The soils were fractionated according to density and particle size to obtain differently stabilized SOM fractions differing in chemical composition and thus bioavailability. To better understand the chemical alterations from plant-derived organic particles in these soils rich in fibrous plant residues to mineralassociated SOM, we analyzed the elemental, isotopic and chemical composition of particulate OM (POM) and claysized mineral-associated OM (MAOM).We demonstrate that the SOM fractions that contribute with about 17 kgCm-3 for more than 60% of the C stock are highly bioavailable and that most of this labile C can be assumed to be prone to mineralization under warming conditions. Thus, the amount of relatively stable, small occluded POM and claysized MAOM that currently accounts with about 10 kgCm-3 for about 40% of the C stock will most probably be crucial for the quantity of C protected from mineralization in these Arctic soils in a warmer future. Using15N as a proxy for nitrogen (N) balances indicated an important role of N inputs by biological N fixation, while gaseous N losses appeared less important. However, this could change, as with about 0.4 kgNm-3 one third of the N is present in bioavailable SOM fractions, which could lead to increases in mineral N cycling and associated N losses under global warming. Our results highlight the vulnerability of SOM in Arctic permafrost-affected soils under rising temperatures, potentially leading to unparalleled greenhouse gas emissions from these soils.
AU  - Prater, I.*
AU  - Zubrzycki, S.*
AU  - Buegger, F.
AU  - Zoor-Fuellgraff, L.C.*
AU  - Angst, G.*
AU  - Dannenmann, M.*
AU  - Mueller, C.W.*
C1  - 59729
C2  - 48997
CY  - Bahnhofsallee 1e, Gottingen, 37081, Germany
SP  - 3367-3383
TI  - From fibrous plant residues to mineral-associated organic carbon - The fate of organic matter in Arctic permafrost soils.
JO  - Biogeosciences
VL  - 17
IS  - 13
PB  - Copernicus Gesellschaft Mbh
PY  - 2020
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - Seasonal variations in monoterpene emissions from Scots pine (Pinus sylvestris) are well documented, and emissions are often shown to follow the incident temperatures due to effects on compound volatility. Recent studies have indicated a link between monoterpene emissions and physiological drivers such as photosynthetic capacity during needle development. The complex interplay between the dynamic changes in the biosynthetic capacity to produce monoterpenes and the temperature-dependent evaporation process of volatiles from internal storage reservoirs has not yet been studied under field conditions. In this study, we analysed the relationships between needle monoterpene synthase activities, endogenous monoterpene storage pools and monoterpene emissions of needles in two consecutive years at a boreal forest site in Finland. The results showed changes in the monoterpene synthase activity of needles, linked to seasonality and needle ontogenesis, while the pool of stored monoterpenes (about 0.5% of dry weight) did not change considerably as a function of needle aging. Monoterpene emissions did not correlate directly with enzyme activity or the storage pool size. We observed notably high plant-to-plant variation in the biosynthesis rates of individual monoterpenes, which did not reflect the storage compound mixture. The enzyme activity producing δ-3-carene was only present in the first months after needle flushing, and decreased with needle age, whereas δ-3-carene was abundant in the endogenous monoterpene pool and dominated the needle emissions. This study emphasizes the seasonal, developmental and intraspecific variability of monoterpene biosynthesis and storage, and calls for more in-depth analyses to reveal how such complex interaction affects monoterpene emissions from pine needles in boreal forests.
AU  - Vanhatalo, A.*
AU  - Ghirardo, A.
AU  - Juurola, E.*
AU  - Schnitzler, J.-P.
AU  - Zimmer, I.
AU  - Hellen, H.*
AU  - Hakola, H.*
AU  - Baeck, J.*
C1  - 54233
C2  - 45334
CY  - Bahnhofsallee 1e, Gottingen, 37081, Germany
SP  - 5047-5060
TI  - Long-term dynamics of monoterpene synthase activities, monoterpene storage pools and emissions in boreal Scots pine.
JO  - Biogeosciences
VL  - 15
IS  - 16
PB  - Copernicus Gesellschaft Mbh
PY  - 2018
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - Regions in the Amazon Basin have been associated with specific biogeochemical processes, but a detailed chemical classification of the abundant and ubiquitous dissolved organic matter (DOM), beyond specific indicator compounds and bulk measurements, has not yet been established. We sampled water from different locations in the Negro, Madeira/Jamari and Tapajo's River areas to characterize the molecular DOM composition and distribution. Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) combined with excitation emission matrix (EEM) fluorescence spectroscopy and parallel factor analysis (PARAFAC) revealed a large proportion of ubiquitous DOM but also unique area-specific molecular signatures. Unique to the DOM of the Rio Negro area was the large abundance of high molecular weight, diverse hydrogen-deficient and highly oxidized molecular ions deviating from known lignin or tannin compositions, indicating substantial oxidative processing of these ultimately plant-derived polyphenols indicative of these black waters. In contrast, unique signatures in the Madeira/Jamari area were defined by presumably labile sulfur-and nitrogen-containing molecules in this white water river system. Waters from the Tapajós main stem did not show any substantial unique molecular signatures relative to those present in the Rio Madeira and Rio Negro, which implied a lower organic molecular complexity in this clear water tributary, even after mixing with the main stem of the Amazon River. Beside ubiquitous DOM at average H/C and O/C elemental ratios, a distinct and significant unique DOM pool prevailed in the black, white and clear water areas that were also highly correlated with EEM-PARAFAC components and define the frameworks for primary production and other aspects of aquatic life.
AU  - Gonsior, M.*
AU  - Valle Das Neves, J.
AU  - Schmitt-Kopplin, P.
AU  - Hertkorn, N.
AU  - Bastviken, D.*
AU  - Luek, J.*
AU  - Harir, M.
AU  - Bastos, W.*
AU  - Enrich-Prast, A.*
C1  - 49228
C2  - 33793
CY  - Gottingen
SP  - 4279-4290
TI  - Chemodiversity of dissolved organic matter in the Amazon Basin.
JO  - Biogeosciences
VL  - 13
IS  - 14
PB  - Copernicus Gesellschaft Mbh
PY  - 2016
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - Wetlands provide quintessential ecosystem services such as maintenance of water quality, water supply and biodiversity, among others; however, wetlands are also among the most threatened ecosystems worldwide. Natural dissolved organic matter (DOM) is an abundant and critical component in wetland biogeochemistry. This study describes the first detailed, comparative, molecular characterization of DOM in subtropical, pulsed, wetlands, namely the Everglades (USA), the Pantanal (Brazil) and the Okavango Delta (Botswana), using optical properties, high-field nuclear magnetic resonance (NMR) and ultrahigh-resolution mass spectrometry (FT-ICRMS), and compares compositional features to variations in organic matter sources and flooding characteristics (i.e., differences in hydroperiod). While optical properties showed a high degree of variability within and between the three wetlands, analogies in DOM fluorescence properties were such that an established excitation emission matrix fluorescence parallel factor analysis (EEM-PARAFAC) model for the Everglades was perfectly applicable to the other two wetlands. Area-normalized 1H NMR spectra of selected samples revealed clear distinctions of samples while a pronounced congruence within the three pairs of wetland DOM readily suggested the presence of an individual wetland-specific molecular signature. Within sample pairs (long- vs. short-hydroperiod sites), internal differences mainly referred to intensity variations (denoting variable abundance) rather than to alterations of NMR resonances positioning (denoting diversity of molecules). The relative disparity was largest between the Everglades long- and short-hydroperiod samples, whereas Pantanal and Okavango samples were more alike among themselves. Otherwise, molecular divergence was most obvious in the case of unsaturated protons (δH > 5 ppm). 2-D NMR spectroscopy for a particular sample revealed a large richness of aliphatic and unsaturated substructures, likely derived from microbial sources such as periphyton in the Everglades. In contrast, the chemical diversity of aromatic wetland DOM likely originates from a combination of higher plant sources, progressive microbial and photochemical oxidation, and contributions from combustion-derived products (e.g., black carbon). FT-ICRMS spectra of both Okavango and Pantanal showed near 57 ± 2 % CHO, 8 ± 2 % CHOS, 33 ± 2 % CHNO and < 1 % CHNOS molecules, whereas those of Everglades samples were markedly enriched in CHOS and CHNOS at the expense of CHO and CHNO compounds. In particular, the Everglades short-hydroperiod site showed a large set of aromatic and oxygen-deficient "black sulfur" compounds whereas the long-hydroperiod site contained oxygenated sulfur attached to fused-ring polyphenols. The elevated abundance of CHOS compounds for the Everglades samples likely results from higher inputs of agriculture-derived and sea-spray-derived sulfate. Although wetland DOM samples were found to share many molecular features, each sample was unique in its composition, which reflected specific environmental drivers and/or specific biogeochemical processes.
AU  - Hertkorn, N.
AU  - Harir, M.
AU  - Cawley, K.M.*
AU  - Schmitt-Kopplin, P.
AU  - Jaffe, R.*
C1  - 48630
C2  - 41238
CY  - Gottingen
SP  - 2257-2277
TI  - Molecular characterization of dissolved organic matter from subtropical wetlands: A comparative study through the analysis of optical properties, NMR and FT-ICR/MS.
JO  - Biogeosciences
VL  - 13
IS  - 8
PB  - Copernicus Gesellschaft Mbh
PY  - 2016
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - Future climate scenarios suggest an increased frequency of summer drought periods in the European Alpine Region. Drought can affect soil nitrogen (N) cycling, by altering N transformation rates, as well as the abundances of ammonia-oxidizing bacteria and archaea. However, the extent to which drought affects N cycling under in situ conditions is still controversial. The goal of this study was to analyse effects of drought on soil N turnover and ammonia-oxidizer abundances. To this end we conducted a rain-exclusion experiment at two differently managed mountain grassland sites, an annually mown and occasionally fertilized meadow and an abandoned grassland. Soils were sampled before, during and after drought and were analysed for gross rates of N mineralization, microbial uptake of inorganic N, nitrification, and the abundances of bacterial and archaeal ammonia oxidizers based on gene copy numbers of the amoA gene (AOB and AOA, respectively). Our results showed that the response to drought differed between the two sites. Effects were stronger at the managed meadow, where NH4+ immobilization rates increased and AOA abundances decreased. At the abandoned site gross nitrification and NO3− immobilization rates decreased during drought, while neither AOB, nor AOA abundances were affected. The different responses of the two sites to drought were likely related to site specific differences, such as soil organic matter content, nitrogen pools and absolute soil water content, resulting from differences in land-management. At both sites rewetting after drought had only minor short-term effects on the parameters that had been affected by drought, and seven weeks after the drought no effects of drought were detectable anymore. Thus, our findings indicate that drought can have distinct transient effects on soil nitrogen cycling and ammonia-oxidizer abundances in mountain grasslands and that the effect strength could be modulated by grassland management.
AU  - Fuchslueger, L.*
AU  - Kastl, E.-M.
AU  - Bauer, F.
AU  - Kienzl, S.*
AU  - Hasibeder, R.*
AU  - Ladreiter-Knauss, T.*
AU  - Schmitt, M.*
AU  - Bahn, M.*
AU  - Schloter, M.
AU  - Richter, A.*
AU  - Szukics, U.*
C1  - 31636
C2  - 34604
SP  - 6003-6015
TI  - Effects of drought on nitrogen turnover and abundances of ammonia-oxidizers in mountain grassland.
JO  - Biogeosciences
VL  - 11
IS  - 21
PY  - 2014
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - Winter air temperatures are projected to increase in the temperate zone, whereas snow cover is projected to decrease, leading to increased soil temperature variability, and potentially to changes in nutrient cycling. Here, we experimentally evaluated the effects of increased winter soil temperature variability on selected aspects of the N-cycle in mesocosms containing different plant community compositions. The experiment was replicated at two sites, a colder mountainous upland site with high snow accumulation and a warmer and drier lowland site. Increased soil temperature variability enhanced soil biotic activity for both sites during winter, as indicated by 35% higher nitrogen (N) availability in the soil solution, 40% higher belowground decomposition and a 25% increase in the potential activity of the enzyme cellobiohydrolase. The mobilization of N differed between sites, and the 15N signal in leaves was reduced by 31% in response to winter warming pulses, but only at the cold site, with significant reductions occurring for three of four tested plant species at this site. Furthermore, there was a trend of increased N leaching in response to the recurrent winter warming pulses. Overall, projected winter climate change in the temperate zone, with less snow and more variable soil temperatures, appears important for shifts in ecosystem functioning (i.e. nutrient cycling). While the effects of warming pulses on plant N mobilization did not differ among sites, reduced plant 15N incorporation at the colder temperate site suggests that frost damage may reduce plant N uptake in a warmer world, with important implications for nitrogen cycling and nitrogen losses from ecosystems.
AU  - Schuerings, J.*
AU  - Jentsch, A.*
AU  - Hammerl, V.
AU  - Lenz, K.*
AU  - Henry, H.A.L.*
AU  - Malyshev, A.V.*
AU  - Kreyling, J.*
C1  - 43008
C2  - 35947
SP  - 7051-7060
TI  - Increased winter soil temperature variability enhances nitrogen cycling and soil biotic activity in temperate heathland and grassland mesocosms.
JO  - Biogeosciences
VL  - 11
IS  - 23
PY  - 2014
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - In initial ecosystems concentrations of all macro- and micronutrients can be considered as extremely low. Plant litter therefore strongly influences the development of a degraders' food web and is an important source for C and N input into soil in such ecosystems. In the present study, a 13C litter decomposition field experiment was performed for 30 weeks in initial soils from a post-mining area near the city of Cottbus (Germany). Two of this regions' dominant but contrasting pioneering plant species (Lotus corniculatus L. and Calamagrostis epigejos L.) were chosen to investigate the effects of litter quality on the litter decomposing microbial food web in initially nutrient-poor substrates. The results clearly indicate the importance of litter quality, mainly the amount of N stored in the litter material and its bioavailability for the degradation process and the development of microbial communities in the detritusphere and bulk soil. Whereas the degradation process of the L. corniculatus litter which had a low C/N ratio was fast and most pronounced changes in the microbial community structure were observed 1–4 weeks after litter addition, the degradation of the C. epigejos litter material was slow and microbial community changes mainly occurred at between 4 and 30 weeks after litter addition to the soil. However for both litter materials a clear indication for the importance of fungi for the degradation process was observed both on the abundance level as well as on the level of 13C incorporation (activity).
AU  - Esperschütz, J.
AU  - Zimmermann, C.*
AU  - Dümig, A.*
AU  - Welzl, G.
AU  - Buegger, F.
AU  - Elmer, M.*
AU  - Munch, J.-C.
AU  - Schloter, M.
C1  - 10846
C2  - 30394
SP  - 5155-5124
TI  - Dynamics of microbial communities during decomposition of litter from pioneering plant in initial soil ecoysystems.
JO  - Biogeosciences
VL  - 10
IS  - 7
PB  - Copernicus Publications
PY  - 2013
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - Abstract. Transformations of dissolved organic matter (DOM) in boreal lakes lead to large greenhouse gas emissions as well as substantial carbon storage in sediments. Using novel molecular characterization approaches and photochemical degradation experiments we studied how seasonal patterns in water column stratification affected the DOM in a Swedish lake under early spring and summer conditions. Dissolved organic carbon (DOC) concentrations were consistently higher above the sediment when compared to surface waters throughout the sampling periods. Photobleaching alone could not explain this difference in DOC because the lake was covered by 40 cm-thick ice during late winter sampling and still showed the same DOC trend. The differences in the molecular diversity between surface DOM in winter and summer were consistent with ongoing photobleaching/decarboxylation and a possible bacterial consumption of photo-products. Additional photo-degradation experiments using simulated sunlight showed a production of highly oxidized organic molecules and low molecular weight compounds in all late winter samples and also in the deep water sample in summer. In the surface summer DOM sample, few such molecules were produced during the photo-degradation experiments, confirming that DOM was already photobleached prior to the experiments. This study suggests that photobleaching, and therefore also the ice cover during winter, plays a central role in surface DOM transformation, with important differences in the molecular composition of DOM between surface and deep boreal lake waters. The release of DOC from boreal lake sediments also contribute to this pattern. Photochemical degradation of DOM may be more extensive following ice-out and water column turnover when non-light exposed and thereby photosensitive DOM is photo-mineralized. Hence, the yearly DOM photo-mineralization may be greater than inferred from studies of recently light-exposed DOM.
AU  - Gonsior, M.*
AU  - Schmitt-Kopplin, P.
AU  - Bastviken, D.*
C1  - 28389
C2  - 33351
SP  - 6945-6956
TI  - Depth-dependent molecular composition and photo-reactivity of dissolved organic matter in a boreal lake under winter and summer conditions.
JO  - Biogeosciences
VL  - 10
IS  - 11
PB  - Copernicus
PY  - 2013
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - High-performance, non-target, high-resolution organic structural spectroscopy was applied to solid phase extracted marine dissolved organic matter (SPE-DOM) isolated from four different depths in the open South Atlantic Ocean off the Angola coast (3 degrees E, 18 degrees S; Angola Basin) and provided molecular level information with extraordinary coverage and resolution. Sampling was performed at depths of 5 m (Angola Current; near-surface photic zone), 48 m (Angola Current; fluorescence maximum), 200 m (still above Antarctic Intermediate Water, AAIW; upper mesopelagic zone) and 5446 m (North Atlantic Deep Water, NADW; abyssopelagic, similar to 30 m above seafloor) and produced SPE-DOM with near 40% carbon yield and beneficial nuclear magnetic resonance (NMR) relaxation properties, a crucial prerequisite for the acquisition of NMR spectra with excellent resolution. H-1 and C-13 NMR spectra of all four marine SPE-DOM showed smooth bulk envelopes, reflecting intrinsic averaging from massive signal overlap, with a few percent of visibly resolved signatures and variable abundances for all major chemical environments. The abundance of singly oxygenated aliphatics and acetate derivatives in H-1 NMR spectra declined from surface to deep marine SPE-DOM, whereas C-based aliphatics and carboxyl-rich alicyclic molecules (CRAM) increased in abundance. Surface SPE-DOM contained fewer methyl esters than all other samples, likely a consequence of direct exposure to sunlight. Integration of C-13 NMR spectra revealed continual increase of carboxylic acids and ketones from surface to depth, reflecting a progressive oxygenation, with concomitant decline of carbohydrate-related substructures. Aliphatic branching increased with depth, whereas the fraction of oxygenated aliphatics declined for methine, methylene and methyl carbon. Lipids in the oldest SPE-DOM at 5446 m showed a larger share of ethyl groups and methylene carbon than observed in the other samples. Two-dimensional NMR spectra showed exceptional resolution and depicted resolved molecular signatures in excess of a certain minimum abundance. Classical methyl groups terminating aliphatic chains represented similar to 15% of total methyl in all samples investigated. A noticeable fraction of methyl (similar to 2%) was bound to olefinic carbon. Methyl ethers were abundant in surface marine SPE-DOM, and the chemical diversity of carbohydrates was larger than that of freshwater and soil DOM. In all samples, we identified sp(2)-hybridized carbon chemical environments with discrimination of isolated and conjugated olefins and alpha,beta-unsaturated double bonds. Olefinic proton and carbon atoms were more abundant than aromatic ones; olefinic unsaturation in marine SPE-DOM will be more directly traceable to ultimate biogenic precursors than aromatic unsaturation. The abundance of furan, pyrrol and thiophene derivatives was marginal, whereas benzene derivatives, phenols and six-membered nitrogen heterocycles were prominent; a yet unassigned set of six-membered N-heterocycles with likely more than one single nitrogen occurred in all samples. Various key polycyclic aromatic hydrocarbon substructures suggested the presence of thermogenic organic matter at all water depths. Progressive NMR cross-peak attenuation from surface to deep marine SPE-DOM was particularly strong in COSY NMR spectra and indicated a continual disappearance of biosignatures as well as entropy gain from an ever increased molecular diversity. Nevertheless, a specific near-seafloor SPE-DOM signature of unsaturated molecules recognized in both NMR and Fourier transform ion cyclotron mass spectrometry (FTICR/MS) possibly originated from sediment leaching. The conformity of key NMR and FTICR/MS signatures suggested the presence of a large set of identical molecules throughout the entire ocean column even though the investigated water masses belonged to different oceanic regimes and currents. FTICR/MS showed abundant CHO, CHNO, CHOS and CHNOS molecular series with slightly increasing numbers of mass peaks and average mass from surface to bottom SPE-DOM. The proportion of CHO and CHNO negative ions increased from surface to depth, whereas CHOS and especially CHNOS molecular series markedly declined. While certain rather aliphatic CHOS and CHNOS ions were observed solely in the surface, deep marine SPE-DOM was enriched in unique unsaturated and rather oxygenated CHO and CHNO molecular series. With the exception of abyssopelagic SPE-DOM at 5446 m, which showed a peculiar CHOS chemistry of unsaturated carbon and reduced sulphur (black sulphur), CHO and CHNO molecular series contributed similar to 87% to total positive electrospray ionization FTICR mass peak integral, with a near constant ratio of CHNO/CHO molecular compositions near 1.13 +/- 0.05. In case of all four marine SPE-DOM, remarkably disparate average elemental compositions as determined from either MS and NMR spectra were observed, caused by a pronounced ionization selectivity in electrospray ionization FTICR/MS. The study demonstrates that the exhaustive characterization of complex unknowns in marine DOM will enable a meaningful classification of individual marine biogeosignatures. Future in-depth functional biodiversity studies with a clear understanding of DOM structure and function might eventually lead to a novel, unified perception of biodiversity and biogeochemistry.
AU  - Hertkorn, N.
AU  - Harir, M.
AU  - Koch, B.P.*
AU  - Michalke, B.
AU  - Schmitt-Kopplin, P.
C1  - 24464
C2  - 31549
SP  - 1583-1624
TI  - High-field NMR spectroscopy and FTICR mass spectrometry: Powerful discovery tools for the molecular level characterization of marine dissolved organic matter.
JO  - Biogeosciences
VL  - 10
IS  - 3
PB  - Copernicus Gesellschaft Mbh
PY  - 2013
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - Legumes can be considered as pioneer plants during ecosystem development, as they form a symbiosis with different nitrogen fixing rhizobia species, which enable the plants to grow on soils with low available nitrogen content. In this study we compared the abundance and diversity of nitrogen fixing microbes based on the functional marker gene nifH, which codes for a subunit of the Fe-protein of the dinitrogenase reductase, in nodules of different size classes of Trifolium arvense (L.). Additionally, carbon and nitrogen contents of the bulk soil and plant material were measured. Plants were harvested from different sites, reflecting 2 (2a) and 5 (5a) yr of ecosystem development, of an opencast lignite mining area in the south of Cottbus, Lower Lusatia (Germany) where the artificial catchment "Chicken Creek" was constructed to study the development of terrestrial ecosystems. Plants from the 5a site revealed higher amounts of carbon and nitrogen, although nifH gene abundances in the nodules and carbon and nitrogen contents between the two soils did not differ significantly. Analysis of the nifH clone libraries showed a significant effect of the nodule size on the community composition of nitrogen fixing microbes. Medium sized nodules (2–5 mm) contained a uniform community composed of Rhizobium leguminosarum bv. trifolii, whereas the small nodules (< 2 mm) consisted of a diverse community including clones with non-Rhizobium nifH gene sequences. Regarding the impact of the soil age on the community composition a clear distinction between the small and the medium nodules can be made. While clone libraries from the medium nodules were pretty similar at both soil ages, soil age had a significant effect on the community compositions of the small nodules, where the proportion of R. leguminosarum bv. trifolii increased with soil age.
AU  - Schulz, S.
AU  - Engel, M.
AU  - Fischer, D.
AU  - Buegger, F.
AU  - Elmer, M.*
AU  - Welzl, G.
AU  - Schloter, M.
C1  - 10402
C2  - 30420
SP  - 1183-1192
TI  - Diversity pattern of nitrogen fixing microbes in nodules of Trifolium arvense (L.) at different initial stages of ecosystem development.
JO  - Biogeosciences
VL  - 10
IS  - 2
PB  - Copernicus Publications
PY  - 2013
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - Soil formation is the result of a complex network of biological as well as chemical and physical processes. Mainly the role of soil microbes is of high interest in this respect, as they are responsible for most transformations and drive the development of stable and labile carbon and nutrient pools in soil, which facilitate the basis for the subsequent establishment of plant communities. Glacier forefields, which provide a chronosequence of soils of different age due to the continuous retreat of the ice layer as a consequence of the increasing annual temperature since the last centuries, are a nice play ground to study the interaction of bacteria, fungi and archaea with their abiotic environment at different stages of soil formation. In this review we give insights into the role of microbes for soil development on the basis of investigations which have been performed at the Damma glacier in Switzerland in the frame of two international network projects Big Link (http://www.cces.ethz.ch/projects/clench/BigLink/) and DFG SFB/TRR 38 (http://www.tu-cottbus.de/ecosystem/). The review focusses on the microbiology of three major steps of soil formation including weathering of the parental material, the development of basic nutrient cycles, the formation of soil crusts and biofilms as initial microbial network structures and the occurrence of plants respectively the setup of plant communities.
AU  - Schulz, S.
AU  - Brankatschk, R.*
AU  - Dümig, A.*
AU  - Kögel-Knabner, I.*
AU  - Schloter, M.
AU  - Zeyer, J.*
C1  - 22471
C2  - 30876
SP  - 3983-3996
TI  - The role of microorganisms at different stages of ecosystem development for soil formation.
JO  - Biogeosciences
VL  - 10
IS  - 6
PB  - Copernicus
PY  - 2013
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - While the importance of anaerobic methane oxidation has been reported for marine ecosystems, the role of this process in soils is still questionable. Grasslands used as pastures for cattle-overwintering show an increase in anaerobic soil micro-sites caused by animal treading and excrement deposition. Therefore anaerobic potential methane oxidation activity of severely impacted soil from a cattle winter pasture was investigated in an incubation experiment under anaerobic conditions using 13C-labeled methane. We were able to detect a high microbial activity utilizing CH4 as nutrient source shown by the respiration of 13CO2. Measurements of possible terminal electron acceptors for anaerobic oxidation of methane were carried out. Soil sulfate concentrations were too low to explain the oxidation of the amount of methane added, but enough nitrate and iron(III) were detected. However, only nitrate was consumed during the experiment. 13C-PLFA analyses clearly showed the utilization of CH4 as nutrient source mainly by organisms harbouring 16:1ω7 PLFAs. These lipids were found in Gram-negative microorganisms and anaerobes. The fact that these lipids are also typical for type I methanotrophs, known as aerobic methane oxidizers, might indicate a link between aerobic and anaerobic methane oxidation.
AU  - Bannert, A.
AU  - Bogen, C.*
AU  - Esperschütz, J.*
AU  - Koubová, A.*
AU  - Buegger, F.
AU  - Fischer, D.
AU  - Radl, V.
AU  - Fuß, R.*
AU  - Chronakova, A.*
AU  - Elhottova, D.*
AU  - Simek, M.*
AU  - Schloter, M.
C1  - 10455
C2  - 30358
SP  - 3891-3899
TI  - Anaerobic oxidation of methane in grassland soils used for cattle husbandry.
JO  - Biogeosciences
VL  - 9
IS  - 10
PB  - Copernicus Publications
PY  - 2012
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - Dissolved organic matter (DOM) was extracted by solid-phase extraction (SPE) from 137 water samples from different climate zones and different depths along an eastern Atlantic Ocean transect. The extracts were analyzed with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with electrospray ionization (ESI). Δ14C analyses were performed on subsamples of the SPE-DOM. In addition, the amount of dissolved organic carbon was determined for all water and SPE-DOM samples as well as the yield of amino sugars for selected samples. Linear correlations were observed between the magnitudes of 43 % of the FT-ICR mass peaks and the extract Δ14C values. Decreasing SPE-DOM Δ14C values went along with a shift in the molecular composition to higher average masses (m/z) and lower hydrogen/carbon (H/C) ratios. The correlation was used to model the SPE-DOM Δ14C distribution for all 137 samples. Based on single mass peaks, a degradation index (IDEG) was developed to compare the degradation state of marine SPE-DOM samples analyzed with FT-ICR MS. A correlation between Δ14C, IDEG, DOC values and amino sugar yield supports that SPE-DOM analyzed with FT-ICR MS reflects trends of bulk DOM. DOM weighted normalized mass peak magnitudes were used to compare aged and recent SPE-DOM on a semi-quantitative molecular basis. The magnitude comparison showed a continuum of different degradation rates for the detected compounds. A high proportion of the compounds should persist, possibly modified by partial degradation, in the course of thermohaline circulation. Prokaryotic (bacterial) production, transformation and accumulation of this very stable DOM occur primarily in the upper ocean. This DOM is an important contribution to very old DOM, showing that production and degradation are dynamic processes.
AU  - Flerus, R.*
AU  - Lechtenfeld, O.J.*
AU  - Koch, B.P.*
AU  - McCallister, S.L.*
AU  - Schmitt-Kopplin, P.
AU  - Benner, R.*
AU  - Kaiser, K.*
AU  - Kattner, G.*
C1  - 8159
C2  - 30003
SP  - 1935-1955
TI  - A molecular perspective on the ageing of marine dissolved organic matter.
JO  - Biogeosciences
VL  - 9
IS  - 6
PB  - Copernicus Gesellschaft mbH
PY  - 2012
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - In order to assess the intrinsic heterogeneity of paddy soils, a set of biogeochemical soil parameters was investigated in five field replicates of seven paddy fields (50, 100, 300, 500, 700, 1000, and 2000 yr of wetland rice cultivation), one flooded paddy nursery, one tidal wetland (TW), and one freshwater site (FW) from a coastal area at Hangzhou Bay, Zhejiang Province, China. All soils evolved from a marine tidal flat substrate due to land reclamation. The biogeochemical parameters based on their properties were differentiated into (i) a group behaving conservatively (TC, TOC, TN, TS, magnetic susceptibility, soil lightness and colour parameters, δ13C, δ15N, lipids and n-alkanes) and (ii) one encompassing more labile properties or fast cycling components (Nmic, Cmic, nitrate, ammonium, DON and DOC). The macroscale heterogeneity in paddy soils was assessed by evaluating intra- versus inter-site spatial variability of biogeochemical properties using statistical data analysis (descriptive, explorative and non-parametric). Results show that the intrinsic heterogeneity of paddy soil organic and minerogenic components per field is smaller than between study sites. The coefficient of variation (CV) values of conservative parameters varied in a low range (10% to 20%), decreasing from younger towards older paddy soils. This indicates a declining variability of soil biogeochemical properties in longer used cropping sites according to progress in soil evolution. A generally higher variation of CV values (>20–40%) observed for labile parameters implies a need for substantially higher sampling frequency when investigating these as compared to more conservative parameters. Since the representativeness of the sampling strategy could be sufficiently demonstrated, an investigation of long-term carbon accumulation/sequestration trends in topsoils of the 2000 yr paddy chronosequence under wetland rice cultivation restricted was conducted. Observations cannot be extrapolated to global scale but with coastal paddy fields developed on marine tidal flat substrates after land reclamation in the Zhejiang Province represent a small fraction (<1%) of the total rice cropping area. The evolutionary trend showed that the biogeochemical signatures characteristic for paddy soils were fully developed in less than 300 yr since onset of wetland rice cultivation. A six-fold increase of topsoil TOC suggests a substantial gain in CO2 sequestration potential when marine tidal wetland substrate developed to 2000 yr old paddy soil.
AU  - Müller-Niggemann, C.*
AU  - Bannert, A.*
AU  - Schloter, M.
AU  - Lehndorff, E.*
AU  - Schwark, L.*
C1  - 7285
C2  - 29645
SP  - 1237-1251
TI  - Intra- versus inter-site macroscale variation in biogeochemical properties along a paddy soil chronosequence.
JO  - Biogeosciences
VL  - 9
IS  - 3
PB  - Copernicus Publications
PY  - 2012
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - Atmospheric aerosols impose direct and indirect effects on the climate system, for example, by absorption of radiation in relation to cloud droplets size, on chemical and organic composition and cloud dynamics. The first step in the formation of Organic primary aerosols, i.e. the transfer of dissolved organic matter from the marine surface into the atmosphere, was studied. We present a molecular level description of this phenomenon using the high resolution analytical tools of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and nuclear magnetic resonance spectroscopy (NMR). Our experiments confirm the chemoselective transfer of natural organic molecules, especially of aliphatic compounds from the surface water into the atmosphere via bubble bursting processes. Transfer from marine surface water to the atmosphere involves a chemical gradient governed by the physicochemical properties of the involved molecules when comparing elemental compositions and differentiating CHO, CHNO, CHOS and CHNOS bearing compounds. Typical chemical fingerprints of compounds enriched in the aerosol phase were CHO and CHOS molecular series, smaller molecules of higher aliphaticity and lower oxygen content, and typical surfactants. A non-targeted metabolomics analysis demonstrated that many of these molecules corresponded to homologous series of oxo-, hydroxy-, methoxy-, branched fatty acids and mono-, di- and tricarboxylic acids as well as monoterpenes and sugars. These surface active biomolecules were preferentially transferred from surface water into the atmosphere via bubble bursting processes to form a significant fraction of primary organic aerosols. This way of sea spray production leaves a selective biological signature of the surface water in the corresponding aerosol that may be transported into higher altitudes up to the lower atmosphere, thus contributing to the formation of secondary organic aerosol on a global scale or transported laterally with possible deposition in the context of global biogeocycling.
AU  - Schmitt-Kopplin, P.
AU  - Liger-Belair, G.*
AU  - Koch, B.P.*
AU  - Flerus, R.*
AU  - Kattner, G.*
AU  - Harir, M.
AU  - Kanawati, B.
AU  - Lucio, M.
AU  - Tziotis, D.
AU  - Hertkorn, N.
AU  - Gebefügi, I.
C1  - 8691
C2  - 29433
SP  - 1571-1582
TI  - Dissolved organic matter in sea spray: A transfer study from marine surface water to aerosols.
JO  - Biogeosciences
VL  - 9
IS  - 4
PB  - Copernicus
PY  - 2012
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - The terrestrial carbon (C) cycle has received increasing interest over the past few decades, however, there is still a lack of understanding of the fate of newly assimilated C allocated within plants and to the soil, stored within ecosystems and lost to the atmosphere. Stable carbon isotope studies can give novel insights into these issues. In this review we provide an overview of an emerging picture of plant-soil-atmosphere C fluxes, as based on C isotope studies, and identify processes determining related C isotope signatures. The first part of the review focuses on isotopic fractionation processes within plants during and after photosynthesis. The second major part elaborates on plant-internal and plant-rhizosphere C allocation patterns at different time scales (diel, seasonal, interannual), including the speed of C transfer and time lags in the coupling of assimilation and respiration, as well as the magnitude and controls of plant-soil C allocation and respiratory fluxes. Plant responses to changing environmental conditions, the functional relationship between the physiological and phenological status of plants and C transfer, and interactions between C, water and nutrient dynamics are discussed. The role of the C counterflow from the rhizosphere to the aboveground parts of the plants, e.g. via CO2 dissolved in the xylem water or as xylem-transported sugars, is highlighted. The third part is centered around belowground C turnover, focusing especially on above- and belowground litter inputs, soil organic matter formation and turnover, production and loss of dissolved organic C, soil respiration and CO2 fixation by soil microbes. Furthermore, plant controls on microbial communities and activity via exudates and litter production as well as microbial community effects on C mineralization are reviewed. The last part of the paper is dedicated to physical interactions between soil CO2 and the soil matrix, such as CO2 diffusion and dissolution processes within the soil profile. From the presented evidence we conclude that there exists a tight coupling of physical, chemical and biological processes involved in C cycling and C isotope fluxes in the plant-soil-atmosphere system. Generally, research using information from C isotopes allows an integrated view of the different processes involved. However, complex interactions among the range of processes complicate or impede the interpretation of isotopic signals in CO2 or organic compounds at the plant and ecosystem level. This is where new research approaches should be aimed at.
AU  - Brüggemann, N.*
AU  - Gessler, A.*
AU  - Kayler, Z.*
AU  - Keel, S. G.*
AU  - Badeck, F.*
AU  - Barthel, M.*
AU  - Boeckx, P.*
AU  - Buchmann, N.*
AU  - Brugnoli, E.*
AU  - Esperschütz, J.
AU  - Gavrichkova, O.*
AU  - Ghashghaie, J.*
AU  - Gomez-Casanovas, N.*
AU  - Keitel, C.*
AU  - Knohl, A.*
AU  - Kuptz, D.*
AU  - Palacio, S.*
AU  - Salmon, Y.*
AU  - Uchida, Y.*
AU  - Bahn, M.*
C1  - 6192
C2  - 28432
SP  - 3457-3489
TI  - Carbon allocation and carbon isotope fluxes in the plant-soil-atmosphere continuum: A review.
JO  - Biogeosciences
VL  - 8
IS  - 2
PB  - Copernicus Gesellschaft mbH
PY  - 2011
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - Microbial food webs are critical for efficient nutrient turnover providing the basis for functional and stable ecosystems. However, the successional development of such microbial food webs and their role in "young" ecosystems is unclear. Due to a continuous glacier retreat since the middle of the 19th century, glacier forefields have expanded offering an excellent opportunity to study food web development at differently developed soils. In the present study, litter degradation and the corresponding C fluxes into microbial communities were investigated along the forefield of the Damma glacier (Switzerland). 13C-enriched litter of the pioneering plant Leucanthemopsis alpina (L.) Heywood was incorporated into the soil at sites that have been free from ice for approximately 10, 60, 100 and more than 700 years. The structure and function of microbial communities were identified by 13C analysis of phospholipid fatty acids (PLFA) and phospholipid ether lipids (PLEL). Results showed increasing microbial diversity and biomass, and enhanced proliferation of bacterial groups as ecosystem development progressed. Initially, litter decomposition proceeded faster at the more developed sites, but at the end of the experiment loss of litter mass was similar at all sites, once the more easily-degradable litter fraction was processed. As a result incorporation of 13C into microbial biomass was more evident during the first weeks of litter decomposition. 13C enrichments of both PLEL and PUFA biomarkers following litter incorporation were observed at all sites, suggesting similar microbial foodwebs at all stages of soil development. Nonetheless, the contribution of bacteria and actinomycetes to litter turnover became more pronounced as soil age increased in detriment of archaea, fungi and protozoa, more prominent in recently deglaciated terrain.
AU  - Esperschütz, J.
AU  - Pérez-de-Mora, A.
AU  - Schreiner, K.
AU  - Welzl, G.
AU  - Buegger, F.
AU  - Zeyer, J.*
AU  - Hagedorn, F.*
AU  - Munch, J.-C.
AU  - Schloter, M.
C1  - 6382
C2  - 28596
SP  - 3283-3294
TI  - Microbial food web dynamics along a soil chronosequence of a glacier forefield.
JO  - Biogeosciences
VL  - 8
IS  - 11
PB  - Copernicus
PY  - 2011
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - Little is known about bacterial dynamics in the oligotrophic ocean, particularly about cultivable bacteria. We examined the abundance of total and cultivable bacteria in relation to changes in biogeochemical conditions in the eastern Atlantic Ocean with special regard to Vibrio spp., a group of bacteria that can cause diseases in human and aquatic organisms. Surface, deep water and plankton (<20 μm, 20–55 μm and >55 μm) samples were collected between 50° N and 24° S. Chlorophyll-a was very low (<0.3 μg l−1) in most areas of the nutrient-poor Atlantic, except at a few locations near upwelling regions. In surface water, dissolved organic carbon (DOC) and nitrogen (DON) concentrations were 64–95 μM C and 2–10 μM N accounting for ≥90 % and ≥76 % of total organic C and N, respectively. DOC and DON gradually decreased to ~45 μM C and <5 μM N in the bottom water. In the surface layer, culture independent total bacteria and other prokaryotes represented by 4´-6-diamidino-2-phenylindole (DAPI) counts, ranged mostly between 107 and 108 cells l−1, while cultivable bacterial counts (CBC) and Vibrio spp. were found at concentrations of 104–107 and 102–105 colony forming units (CFU) l−1, respectively. Most bacteria (>99 %) were found in the nanoplankton fraction (<20 μm), however, bacterial abundance did not correlate with suspended particulates (chlorophyll-a, particulate organic C [POC] and N [PON]). Instead, we found a highly significant correlation between bacterial abundance and temperature (p < 0.001) and a significant correlation with DOC and DON (p < 0.005 and <0.01, respectively). In comparison to CBC and DAPI-stained prokaryotes, cultivable Vibrio showed a stronger and highly significant correlation with DOC and DON (p < 0.0005 and p < 0.005, respectively). In cold waters of the mesopelagic and abyssal zones, CBC was 50 to 100-times lower than in the surface layer; however, cultivable Vibrio spp. could be isolated from the bathypelagic zone and even near the seafloor (average ~10 CFU l−1). The depth-wise decrease in CBC and Vibrio coincided with the decrease in both DOC and POC. Our study indicates that Vibrio and other bacteria may largely depend on dissolved organic matter to survive in nutrient-poor oceanic habitats.
AU  - Neogi, S.B.*
AU  - Koch, B.P.*
AU  - Schmitt-Kopplin, P.
AU  - Pohl, C.*
AU  - Kattner, G.*
AU  - Yamasaki, S.*
AU  - Lara, R.J.*
C1  - 6830
C2  - 29327
SP  - 3747-3759
TI  - Biogeochemical controls on the bacterial populations in the eastern Atlantic Ocean.
JO  - Biogeosciences
VL  - 8
IS  - 12
PB  - Copernicus Publications
PY  - 2011
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - Nitric oxide (NO) plays an important role in the photochemistry of the troposphere. NO from soil contributes up to 40% to the global budget of atmospheric NO. Soil NO emissions are primarily caused by biological activity (nitrification and denitrification), that occurs in the uppermost centimeter of the soil, a soil region often characterized by high contents of organic material. Most studies of NO emission potentials to date have investigated mineral soil layers. In our study we sampled soil organic matter under different understories (moss, grass, spruce and blueberries) in a humid mountainous Norway spruce forest plantation in the Fichtelgebirge (Germany). We performed laboratory incubation and flushing experiments using a customized chamber technique to determine the response of net potential NO flux to physical and chemical soil conditions (water content and temperature, bulk density, particle density, pH, C/N ratio, organic C, soil ammonium, soil nitrate). Net potential NO fluxes (in terms of mass of N) from soil samples taken under different understories ranged from 1.7-9.8 ng m(-2) s(-1) (soil sampled under grass and moss cover), 55.4-59.3 ng m(-2) s(-1) (soil sampled under spruce cover), and 43.7-114.6 ng m(-2) s(-1) (soil sampled under blueberry cover) at optimum water content and a soil temperature of 10 degrees C. The water content for optimum net potential NO flux ranged between 0.76 and 0.8 gravimetric soil moisture for moss covered soils, between 1.0 and 1.1 for grass covered soils, 1.1 and 1.2 for spruce covered soils, and 1.3 and 1.9 for blueberry covered soils. Effects of soil physical and chemical characteristics on net potential NO flux were statistically significant (0.01 probability level) only for NH4+. Therefore, as an alternative explanation for the differences in soil biogenic NO emission we consider more biological factors like understory vegetation type, amount of roots, and degree of mycorrhization; they have the potential to explain the observed differences of net potential NO fluxes.
AU  - Bargsten, A.*
AU  - Falge, E.*
AU  - Pritsch, K.
AU  - Huwe, B.*
AU  - Meixner, F.X.*
C1  - 5549
C2  - 27605
SP  - 1425-1441
TI  - Laboratory measurements of nitric oxide release from forest soil with a thick organic layer under different understory types.
JO  - Biogeosciences
VL  - 7
IS  - 5
PB  - Copernicus
PY  - 2010
SN  - 1726-4170
ER  - 

TY  - JOUR
AB  - Numerous studies have dealt with carbon (C) contents in Histosols, but there are no studies quantifying the relative importance of the individual C components in pore waters. For this study, measurements were taken of all the carbon components (particulate organic carbon, POC; dissolved organic carbon, DOC; dissolved inorganic carbon, DIC; dissolved methane, CH4) in the soil pore water of calcareous fens under three different water management regimes (re-wetted, deeply and moderately drained). Pore water was collected weekly or biweekly (April 2004 to April 2006) at depths between 10 and 150 cm. The main results obtained were: (1) DIC (94–280 mg C l-1) was the main C-component. (2) POC and DOC concentrations in the pore water (14–125 mg C l-1 vs. 41–95 mg C l-1) were pari passu. (3) Dissolved CH4 was the smallest C component (0.005–0.9 mg C l-1). Interestingly, about 30% of the POM particles were colonized by microbes indicating that they are active in the internal C turnover. Certainly, both POC and DOC fractions are essential components of the C budget of peatlands. Furthermore, dissolved CO2 in all forms of DIC appears to be an important part of peatland C-balance.
AU  - Fiedler, S.*
AU  - Höll, S.*
AU  - Freibauer, A.*
AU  - Stahr, K.*
AU  - Drösler, M.*
AU  - Schloter, M.
AU  - Jungkunst, H.F.*
C1  - 5010
C2  - 25929
SP  - 1615-1623
TI  - Particulate organic carbon (POC) in relation to other pore water carbon fractions in drained and rewetted fens in Southern Germany.
JO  - Biogeosciences
VL  - 5
IS  - SI
PB  - Copernicus
PY  - 2008
SN  - 1726-4170
ER  -