Short-term bioavailability of carbon in soil organic matter fractions of different particle sizes and densities in grassland ecosystems

Breulmann, Marc; Masyutenko, N. P.; Когут, Б. М.; Schroll, Reiner; Dörfler, Ulrike; Buscot, François; Schulz, Elke

doi:10.1016/j.scitotenv.2014.07.080

Cited by 58 publications

(25 citation statements)

References 44 publications

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“…However, in the semiarid soils of the studied transect, particulate OC contributed < 10 % of bulk OC, while mineral-bound OC accounted for > 90 % (Table 3). This contrasts with observations from the steppe soils (mostly Chernozems) of European Russia (Breulmann et al, 2014;Kalinina et al, 2011), Canada (Plante et al, 2010), and China (Steffens et al, 2010) in which particulate OC represented > 20 % of bulk OC. Nevertheless, our results are in line with Bischoff et al (2016), who reported that a maximum of 10 % OC was present as particulate OC in the Chernozems and Kastanozems of the Kulunda steppe.…”

Section: Partitioning and Composition Of Soil Om In Functionally Diffcontrasting

confidence: 88%

Organic matter dynamics along a salinity gradient in Siberian steppe soils

et al. 2018

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Abstract. Salt-affected soils will become more frequent in the next decades as arid and semiarid ecosystems are predicted to expand as a result of climate change. Nevertheless, little is known about organic matter (OM) dynamics in these soils, though OM is crucial for soil fertility and represents an important carbon sink. We aimed at investigating OM dynamics along a salinity and sodicity gradient in the soils of the southwestern Siberian Kulunda steppe (Kastanozem, non-sodic Solonchak, Sodic Solonchak) by assessing the organic carbon (OC) stocks, the quantity and quality of particulate and mineral-associated OM in terms of non-cellulosic neutral sugar contents and carbon isotopes (δ 13 C, 14 C activity), and the microbial community composition based on phospholipid fatty acid (PLFA) patterns. Aboveground biomass was measured as a proxy for plant growth and soil OC inputs. Our hypotheses were that (i) soil OC stocks decrease along the salinity gradient, (ii) the proportion and stability of particulate OM is larger in salt-affected Solonchaks compared to non-salt-affected Kastanozems, (iii) sodicity reduces the proportion and stability of mineral-associated OM, and (iv) the fungi : bacteria ratio is negatively correlated with salinity. Against our first hypothesis, OC stocks increased along the salinity gradient with the most pronounced differences between topsoils. In contrast to our second hypothesis, the proportion of particulate OM was unaffected by salinity, thereby accounting for only < 10 % in all three soil types, while mineral-associated OM contributed > 90 %. Isotopic data (δ 13 C, 14 C activity) and neutral sugars in the OM fractions indicated a comparable degree of OM transformation along the salinity gradient and that particulate OM was not more persistent under saline conditions. Our third hypothesis was also rejected, as Sodic Solonchaks contained more than twice as much mineral-bound OC than the Kastanozems, which we ascribe to the flocculation of OM and mineral components under higher ionic strength conditions. Contrary to the fourth hypothesis, the fungi : bacteria ratio in the topsoils remained fairly constant along the salinity gradient. A possible explanation for why our hypotheses were not affirmed is that soil moisture covaried with salinity along the transect, i.e., the Solonchaks were generally wetter than the Kastanozems. This might cause comparable water stress conditions for plants and microorganisms, either due to a low osmotic or a low matric potential and resulting in (i) similar plant growth and hence soil OC inputs along the transect, (ii) a comparable persistence of particulate OM, and (iii) unaffected fungi : bacteria ratios. We conclude that saltaffected soils contribute significantly to the OC storage in the semiarid soils of the Kulunda steppe, while most of the Published by Copernicus Publications on behalf of the European Geosciences Union. 14 N. Bischoff et al.: Organic matter dynamics along a salinity gradient OC is associated with minerals and is therefore effectively s...

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Section: Partitioning and Composition Of Soil Om In Functionally Diffcontrasting

confidence: 88%

Organic matter dynamics along a salinity gradient in Siberian steppe soils

et al. 2018

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“…() suggest micro‐niches in biofilms select for specific organisms and repel poorly‐adapted immigrating species. Indeed, substrate features may impose strong environmental filters on microbiomes – sediment geochemistry (Carson et al ., ; Jorgensen et al ., ) and matrix structure (Vos et al ., ; Breulmann et al ., ) can select for traits that enhance attachment on a particular substrate.…”

Section: Discussionmentioning

confidence: 97%

Deterministic influences exceed dispersal effects on hydrologically‐connected microbiomes

Graham

Crump

Resch

et al. 2017

Environmental Microbiology

142

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Subsurface groundwater-surface water mixing zones (hyporheic zones) have enhanced biogeochemical activity, but assembly processes governing subsurface microbiomes remain a critical uncertainty in understanding hyporheic biogeochemistry. To address this obstacle, we investigated (a) biogeographical patterns in attached and waterborne microbiomes across three hydrologically-connected, physicochemically-distinct zones (inland hyporheic, nearshore hyporheic and river); (b) assembly processes that generated these patterns; (c) groups of organisms that corresponded to deterministic changes in the environment; and (d) correlations between these groups and hyporheic metabolism. All microbiomes remained dissimilar through time, but consistent presence of similar taxa suggested dispersal and/or common selective pressures among zones. Further, we demonstrated a pronounced impact of deterministic assembly in all microbiomes as well as seasonal shifts from heterotrophic to autotrophic microorganisms associated with increases in groundwater discharge. The abundance of one statistical cluster of organisms increased with active biomass and respiration, revealing organisms that may strongly influence hyporheic biogeochemistry. Based on our results, we propose a conceptualization of hyporheic zone metabolism in which increased organic carbon concentrations during surface water intrusion support heterotrophy, which succumbs to autotrophy under groundwater discharge. These results provide new opportunities to enhance microbially-explicit ecosystem models describing hyporheic zone biogeochemistry and its influence over riverine ecosystem function.

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“…Variation in assembly processes between attached and planktonic communities may be due to inherent differences among these environments, such as influences of mineralogy (Carson et al, 2007; Jorgensen et al, 2012), physical matrix composition (Vos et al, 2013; Breulmann et al, 2014), and/or relative rates of change in environment characteristics (discussed below). Further, differences in assembly processes and niche dynamics between the attached and planktonic communities may also be reflective of differing rates of organismal response to fluctuations in the hyporheic environment.…”

Section: Discussionmentioning

confidence: 99%

Coupling Spatiotemporal Community Assembly Processes to Changes in Microbial Metabolism

et al. 2016

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Community assembly processes generate shifts in species abundances that influence ecosystem cycling of carbon and nutrients, yet our understanding of assembly remains largely separate from ecosystem-level functioning. Here, we investigate relationships between assembly and changes in microbial metabolism across space and time in hyporheic microbial communities. We pair sampling of two habitat types (i.e., attached and planktonic) through seasonal and sub-hourly hydrologic fluctuation with null modeling and temporally explicit multivariate statistics. We demonstrate that multiple selective pressures—imposed by sediment and porewater physicochemistry—integrate to generate changes in microbial community composition at distinct timescales among habitat types. These changes in composition are reflective of contrasting associations of Betaproteobacteria and Thaumarchaeota with ecological selection and with seasonal changes in microbial metabolism. We present a conceptual model based on our results in which metabolism increases when oscillating selective pressures oppose temporally stable selective pressures. Our conceptual model is pertinent to both macrobial and microbial systems experiencing multiple selective pressures and presents an avenue for assimilating community assembly processes into predictions of ecosystem-level functioning.

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Short-term bioavailability of carbon in soil organic matter fractions of different particle sizes and densities in grassland ecosystems

Cited by 58 publications

References 44 publications

Organic matter dynamics along a salinity gradient in Siberian steppe soils

Organic matter dynamics along a salinity gradient in Siberian steppe soils

Deterministic influences exceed dispersal effects on hydrologically‐connected microbiomes

Coupling Spatiotemporal Community Assembly Processes to Changes in Microbial Metabolism

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