Browsing by Subject "Microbial biomass"

Now showing 1 - 3 of 3

Litter quality and microbes explain aggregation differences in a tropical sandy soil
(2022) Laub, Moritz; Schlichenmeier, Samuel; Vityakon, Patma; Cadisch, Georg
Soil aggregates store most soil organic carbon (SOC), but how does litter quality influence their formation? We hypothesized varying litter quality to facilitate differences in aggregate formation by altering the seasonal development of microbial biomass (MB) C and N, with MB driving aggregate development in a tropical sandy soil in Thailand. Aggregate development was studied in a long-term fallow experiment, receiving 10 Mg ha−1 annual applications of rice (Oryza sativa) straw (low N and polyphenols (PP)), groundnut (Arachis hypogaea) stover (high N, low PP), tamarind (Tamarindus indica) litter (medium N and PP), or dipterocarp (Dipterocarpus tuberculatus) leaf litter (low N, high PP) compared to a control. N-rich litter from groundnut and tamarind led to significantly higher MB, bulk soil C and aggregate C than dipterocarp, rice straw, and the control. Bulk soil C and small macroaggregates C of N-rich litter treatments increased about 7% in 30 weeks. Increasing MB N explained increasing small macroaggregate C and both, MB C or N were important covariates explaining temporal variations of C stored in themicroaggregates, in silt and clay. MB also explained temporal variations of aggregate fraction weights. With time, SMA C only increased in the N-rich groundnut and tamarind treatments, but decreased in other treatments. Connections of MB to aggregate C and weight substantiated the importance of microbial activity for aggregate formation and carbon sequestration. By promoting MB for longest time spans, medium-quality tamarind could best facilitateaggregate formation, and increase silt and clay C.
Microbial drivers of plant richness and productivity in a grassland restoration experiment along a gradient of land‐use intensity
(2022) Abrahão, Anna; Marhan, Sven; Boeddinghaus, Runa S.; Nawaz, Ali; Wubet, Tesfaye; Hölzel, Norbert; Klaus, Valentin H.; Kleinebecker, Till; Freitag, Martin; Hamer, Ute; Oliveira, Rafael S.; Lambers, Hans; Kandeler, Ellen
Plant–soil feedbacks (PSFs) underlying grassland plant richness and productivity are typically coupled with nutrient availability; however, we lack understanding of how restoration measures to increase plant diversity might affect PSFs. We examined the roles of sward disturbance, seed addition and land‐use intensity (LUI) on PSFs. We conducted a disturbance and seed addition experiment in 10 grasslands along a LUI gradient and characterized plant biomass and richness, soil microbial biomass, community composition and enzyme activities. Greater plant biomass at high LUI was related to a decrease in the fungal to bacterial ratios, indicating highly productive grasslands to be dominated by bacteria. Lower enzyme activity per microbial biomass at high plant species richness indicated a slower carbon (C) cycling. The relative abundance of fungal saprotrophs decreased, while pathogens increased with LUI and disturbance. Both fungal guilds were negatively associated with plant richness, indicating the mechanisms underlying PSFs depended on LUI. We show that LUI and disturbance affect fungal functional composition, which may feedback on plant species richness by impeding the establishment of pathogen‐sensitive species. Therefore, we highlight the need to integrate LUI including its effects on PSFs when planning for practices that aim to optimize plant diversity and productivity.
The stonesphere in agricultural soils: a microhabitat associated with rock fragments bridging rock and soil
(2024) Dittrich, Felix; Klaes, Björn; Brandt, Luise; Groschopf, Nora; Thiele‐Bruhn, Sören
Rock fragments (RFs) are abundant soil constituents, but are routinely excluded from soil analyses. Hence, their contribution to soil properties, and in particular to the microbiome, is incompletely understood. Therefore, shifts in microbial colonisation along the rock‐to‐soil continuum of topsoils from three agricultural sites with different sedimentary parent rock materials were investigated with particular attention to RFs. Microbial biomass and community composition were quantified using phospholipid fatty acid (PLFA) analysis for unweathered and weathered parent rock materials, two RF fractions (8–16 mm and 2–8 mm) and the fine earth (FE; <2 mm). Trends in biogeochemical weathering, nutrient availability and soil organic matter (OM) development were assessed using mineralogical, geochemical and physical analyses. Actinobacterial PLFA was particularly abundant in parent rocks, where Actinobacteria likely contribute to rock weathering and the initiation of OM accumulation. Conversely, bacterial PLFAs were most abundant in the FE under nutrient‐ and OM‐rich conditions. The integral role of RFs as a microbial habitat is demonstrated by a distinct fungal colonisation, which is enabled by the specific physical features of RFs in combination with the provision of inorganic nutrients. Our findings indicate that RFs are colonised by microbes and that differences in the community structure depend on mineralogical properties and chemical weathering status. We document that RFs are microhabitats with a significant potential to host microbial life in cultivated soils, and thus, could play an important role in biogeochemical cycling and the provision of soil functions in agroecosystems.