Recent global declines in biodiversity in response to climate change have sparked major concerns among scientists, citizens, and policy makers. Yet, potential mechanisms underlying soil microbial biodiversity and ecosystem functioning (BEF) relationships remain vague and, to date, the effect of climate change factors on such relationships has not been assessed. To study the impacts of climate warming conditions on BEF relationships, we used soils treated with either field-warmed or ambient-control conditions from a grassland in Central Oklahoma to establish biodiversity gradients in laboratory microcosms. A clear diversity gradient was achieved by combining both size-fractionation and dilution-series techniques. The generated microcosms were monitored to assess microbial functioning (respiration, speciation of soil nutrients, and decomposition) and bacterial phylogenetic diversity using 16s rRNA gene sequencing. The microcosms were amended initially with nitrate fertilizer then 3 months later with switchgrass litter. Community diversity and soil nutrients (ammonium and nitrate N, soluble P, organic matter, total C and N) were assessed directly prior to each input and again 3 months following to assess the responses to N and C inputs.
Results/Conclusions
Our data show significant variation in the functional activities and potentials of communities in soils with reduced trophic-level and bacterial phylogenetic diversities as compared to those with more complex communities. In particular, the diversity gradient had a significant effect on soil N cycling processes and significant shifts in N-speciation were correlated with the exclusion of soil mesofauna. Additionally, multifunctionality showed a greater dependence on soil biodiversity in microcosms prepared from field-warmed soil as compared to ambient-control treated soils. This suggests that in warmed conditions ecosystem functioning could be more sensitive to losses of biodiversity, reflecting an additional major impact of climate change.