Abstract
Microbial respiration is critical for soil carbon balance and ecosystem functioning. Previous studies suggest that plant diversity influences soil microbial communities and their respiration. Yet, the linkages between tree diversity, microbial biomass, microbial diversity, and microbial functioning have rarely been explored. In this study, we measured two microbial functions (microbial physiological potential, and microbial respiration), together with microbial biomass, microbial taxonomic and functional profiles, and soil chemical properties in a tree diversity experiment in South China, to disentangle how tree diversity affects microbial respiration through the modifications of the microbial community. Our analyses show a significant positive effect of tree diversity on microbial biomass (+25% from monocultures to 24-species plots), bacterial diversity (+12%), and physiological potential (+12%). In addition, microbial biomass and physiological potential, but not microbial diversity, were identified as the key drivers of microbial respiration. Although soil chemical properties strongly modulated soil microbial community, tree diversity increased soil microbial respiration by increasing microbial biomass rather than changing microbial taxonomic or functional diversity. Overall, our findings suggest a prevalence of microbial biomass over diversity in controlling soil carbon dynamics.
Highlights
A thorough understanding of the soil carbon balance is essential to mitigate recent increases in atmospheric carbon concentrations and the resulting climate change [1,2,3,4]
Tree diversity enhances the soil microbial biomass, diversity and functions Our analyses showed that tree species richness enhanced soil microbial community properties and functions
The tree diversity effect on total biomass and basal respiration were mostly driven by high values in 24-species tree communities for microbial biomass and lower variability for respiration (Fig. 2, Supplementary S7A)
Summary
A thorough understanding of the soil carbon balance is essential to mitigate recent increases in atmospheric carbon concentrations and the resulting climate change [1,2,3,4]. Plant diversity can increase litter and rhizosphere carbon inputs into the soil, thereby enhancing the quality and quantity of resources for the soil microbial community [21, 22]. This increase of rhizosphere carbon was shown to enhance soil carbon storage [19, 23] by increasing soil microbial biomass and activity [19, 24]. Abiotic conditions, such as climate and soil chemical properties (soil carbon, nitrogen and phosphorus concentrations, pH, and humidity) drive the assembly and functioning of soil microbial communities [12, 13, 25, 26]. The effect of abiotic conditions on soil microbes greatly depends on which facet of the microbiota is assessed [30,31,32]
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