Soil microbial carbon consumption affected by tree and mammal diversity

Abstract

Trees, mammals, and microbes relate to soil carbon (C) cycle. Trees capture C, and mammals consume plants and other animals, both contributing to organic remains that are then degraded by soil microbes. This organic C can be stored in soils or released into the atmosphere through microbial mineralization. Yet, the simultaneous effects of mammals and trees on C consumption by soil microbes have not been investigated. For 30 sampling sites in a mixed forest-savanna environment in southern Guyana, we jointly analyzed observational data of mammal and tree communities along with soil organic matter (SOM) composition (using Fourier transform infrared spectroscopy combined with attenuated total reflectance, energy dispersive X-ray fluorescence spectrometry, and CNH elemental analyzer) and soil microbial C consumption (using Biolog EcoPlates). It was found that higher mammal functional richness (FRic) and functional evenness (FEve) were related to reduced overall C consumption by soil microbes (for FRic: regression coefficient (β) = -0.010, standard error (SE) = 0.005, P = 0.034; for FEve: β = -0.012, SE = 0.005, P = 0.010) with the coefficient of determination (R2) value of 0.359, explaining 36% of the variance in average well color development values, whereas a higher tree richness was associated with a reduced diversity of C sources consumed by soil microbial communities (β = -0.353, SE = 0.172, P = 0.041) with the R2 value of 0.290, explaining 29% of the variance in Shannon diversity index values. Our results indicate that mammal and tree communities have complementary effects on soil microbial C consumption, improving our understanding of the functioning of C cycle in the high-diversity Amazon biome. These findings are crucial in elucidating the intricate connections between above- and belowground biodiversity that influence the accumulation and stabilization of soil organic C.