Abstract
Soil bacterial diversity varies across biomes with potential impacts on soil ecological functioning. Here, we incorporate key factors that affect soil bacterial abundance and diversity across spatial scales into a mechanistic modeling framework considering soil type, carbon inputs and climate towards predicting soil bacterial diversity. The soil aqueous-phase content and connectivity exert strong influence on bacterial diversity for each soil type and rainfall pattern. Biome-specific carbon inputs deduced from net primary productivity provide constraints on soil bacterial abundance independent from diversity. The proposed heuristic model captures observed global trends of bacterial diversity in good agreement with predictions by an individual-based mechanistic model. Bacterial diversity is highest at intermediate water contents where the aqueous phase forms numerous disconnected habitats and soil carrying capacity determines level of occupancy. The framework delineates global soil bacterial diversity hotspots; located mainly in climatic transition zones that are sensitive to potential climate and land use changes.
Highlights
Soil bacterial diversity varies across biomes with potential impacts on soil ecological functioning
The heuristic model (HM) assumes that a certain proportion of the annual NPPderived organic carbon input is allocated to bacteria (24% of net primary productivity (NPP) for bacterial respiration28,29)
We found that varying the range of expected values (14–30% of NPP28) had little impact on estimates of carrying capacity
Summary
Soil bacterial diversity varies across biomes with potential impacts on soil ecological functioning. Quantifying the roles of soil factors, such as soil texture, porosity and hydration conditions in relation to climate and vegetation cover, is an important step towards disentangling bacterial diversity and abundance as suggested by recent empirical evidence[17]. Soil chemical properties such as pH2,14,17,19 and organic carbon content[15,16,17] together with climatic attributes, such as aridity index[15], precipitation[2,17] and temperature[13], have been identified as important explanatory variables. The framework expresses soil bacterial diversity at two interlinked spatial scales: at the single aqueous habitat scale and at the soil sample scale that can contain many isolated aqueous habitats
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