【真菌与细菌的生理差异改变土壤C、N循环】Bonnie G. Waring* Colin Averill Christine V. Hawkes. Differences in fungal and bacterial physiology alter soil carbon and nitrogen cycling: insights from meta-analysis and theoretical models. Ecology Letters
Abstract
Since fungi and bacteria are the dominant decomposers in soil their distinct physiologies are likely to differentially influence rates of ecosystem carbon (C) and nitrogen (N) cycling. We used meta-analysis and an enzyme-driven biogeochemical model to explore the drivers and biogeochemical consequences of changes in the fungal-to-bacterial ratio (F : B). In our meta-analysis data set F : B increased with soil C : N ratio (R2 = 0.224 P < 0.001) a relationship predicted by our model. We found that differences in biomass turnover rates influenced F : B under conditions of C limitation while differences in biomass stoichiometry set the upper bounds on F : B once a nutrient limitation threshold was reached. Ecological interactions between the two groups shifted along a gradient of resource stoichiometry. At intermediate substrate C : N fungal N mineralisation fuelled bacterial growth increasing total microbial biomass and decreasing net N mineralisation. Therefore we conclude that differences in bacterial and fungal physiology may have large consequences for ecosystem-scale C and N cycling.
【微生物群落的C利用率】Robert L. Sinsabaugh1* Stefano Manzoni2 Daryl L. Moorhead3 Andreas Richter4. Carbon use efficiency of microbial communities: stoichiometry methodology and modelling. Ecology Letters
Abstract
Carbon use efficiency (CUE) is a fundamental parameter for ecological models based on the physiology of microorganisms. CUE determines energy and material flows to higher trophic levels conversion of plant-produced carbon into microbial products and rates of ecosystem carbon storage. Thermodynamic calculations support a maximum CUE value of ~ 0.60 (CUE max). Kinetic and stoichiometric constraints on microbial growth suggest that CUE in multi-resource limited natural systems should approach ~ 0.3 (CUE max-2). However the mean CUE values reported for aquatic and terrestrial ecosystems differ by twofold (~ 0.26 vs. ~ 0.55) because the methods used to estimate CUE in aquatic and terrestrial systems generally differ and soil estimates are less likely to capture the full maintenance costs of community metabolism given the difficulty of measurements in water-limited environments. Moreover many simulation models lack adequate representation of energy spilling pathways and stoichiometric constraints on metabolism which can also lead to overestimates of CUE. We recommend that broad-scale models use a