Despite the vital role of microorganisms for ecosystem functioning and human welfare, our understanding of their global diversity and biogeographical patterns lags significantly behind that of plants and animals. We conducted a meta‐analysis including ~600 soil samples from all continents to evaluate the biogeographical patterns and drivers of bacterial diversity in terrestrial ecosystems at the global scale. Similar to what has been found with plants and animals, the diversity of soil bacteria in the Southern Hemisphere decreased from the equator to Antarctica. However, soil bacteria showed similar levels of diversity across the Northern Hemisphere. The composition of bacterial communities followed dissimilar patterns between hemispheres, as the Southern and Northern Hemispheres were dominated by Actinobacteria and Acidobacteria, respectively. However, Proteobacteria was co‐dominant in both hemispheres. Moreover, we found a decrease in soil bacterial diversity with altitude. Climatic features (e.g., high diurnal temperature range and low temperature) were correlated with the lower diversity found at high elevations, but geographical gradients in soil total carbon and species turnover were important drivers of the observed latitudinal patterns. We thus found both parallels and differences in the biogeographical patterns of aboveground vs. soil bacterial diversity. Our findings support previous studies that highlighted soil pH, spatial influence, and organic matter as important drivers of bacterial diversity and composition. Furthermore, our results provide a novel integrative view of how climate and soil factors influence soil bacterial diversity at the global scale, which is critical to improve ecosystem and earth system simulation models and for formulating sustainable ecosystem management and conservation policies.

Agronomic practices such as crop residue return and additional nutrient supply are recommended to increase soil organic carbon (SOC) in arable farmlands. However, changes in the priming effect (PE) on native SOC mineralization in response to integrated inputs of residue and nutrients are not fully known. This knowledge gap along with a lack of understanding of microbial mechanisms hinders the ability to constrain models and to reduce the uncertainty to predict carbon (C) sequestration potential. Using a C-labeled wheat residue, this 126-day incubation study examined the dominant microbial mechanisms that underpin the PE response to inputs of wheat residue and nutrients (nitrogen, phosphorus and sulfur) in two contrasting soils. The residue input caused positive PE through "co-metabolism," supported by increased microbial biomass, C and nitrogen (N) extracellular enzyme activities (EEAs), and gene abundance of certain microbial taxa (Eubacteria, β-Proteobacteria, Acidobacteria, and Fungi). The residue input could have induced nutrient limitation, causing an increase in the PE via "microbial nutrient mining" of native soil organic matter, as suggested by the low C-to-nutrient stoichiometry of EEAs. At the high residue, exogenous nutrient supply (cf. no-nutrient) initially decreased positive PE by alleviating nutrient mining, which was supported by the low gene abundance of Eubacteria and Fungi. However, after an initial decrease in PE at the high residue with nutrients, the PE increased to the same magnitude as without nutrients over time. This suggests the dominance of "microbial stoichiometry decomposition," supported by higher microbial biomass and EEAs, while Eubacteria and Fungi increased over time, at the high residue with nutrients cf. no-nutrient in both soils. Our study provides novel evidence that different microbial mechanisms operate simultaneously depending on organic C and nutrient availability in a residue-amended soil. Our results have consequences for SOC modeling and integrated nutrient management employed to increase SOC in arable farmlands.

Soil carbon (C) stabilisation is known to depend in part on its distribution in structural aggregates, and upon soil microbial activity within the aggregates. However, the mechanisms and relative contributions of different microbial groups to C turnover in different aggregates under various management practices remain unclear. The aim of this study was to determine the role of soil aggregation and their associated microbial communities in driving the responses of soil organic matter (SOM) to multiple management practices. Our results demonstrate that higher amounts of C inputs coupled with greater soil aggregation in residue retention management practices has positive effects on soil C content. Our results provide evidence that different aggregate size classes support distinct microbial habitats which supports the colonisation of different microbial communities. Most importantly our results indicate that the effects of management practices on soil C is modulated by soil aggregate sizes and their associated microbial community and are more pronounced in macro-aggregate compared with micro-aggregate sizes. Based on our findings we recommend that differential response of management practices and microbial control on the C turnover in macro-aggregates and micro-aggregate should be explicitly considered when accounting for management impacts on soil C turnover.

In this paper, we investigate the properties of generalized bent functions defined on Z n 2 with values in Z q , where q ≥ 2 is any positive integer. We characterize the class of generalized bent functions symmetric with respect to two variables, provide analogues of Maiorana-McFarland type bent functions and Dillon's functions in the generalized set up. A class of bent functions called generalized spreads is introduced and we show that it contains all Dillon type generalized bent functions and Maiorana-McFarland type generalized bent functions. Thus, unification of two different types of generalized bent functions is achieved. The crosscorrelation spectrum of generalized Dillon type bent functions is also characterized. We further characterize generalized bent Boolean functions defined on Z n 2 with values in Z 4 and Z 8 . Moreover, we propose several constructions of such generalized bent functions for both n even and n odd.

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