Data from: Effects of plant functional group loss on soil biota and net ecosystem exchange: a plant removal experiment in the Mongolian grassland

1. The rapid loss of global biodiversity can greatly affect the
functioning of above-ground components of ecosystems. However, how such
biodiversity losses affect below-ground communities and linkages to soil
carbon (C) sequestration is unclear. Here we describe how losses in plant
functional groups (PFGs) affect soil microbial and nematode communities
and net ecosystem exchange (NEE) in a 4-year removal experiment conducted
on the Mongolian plateau, the world's largest remaining natural
grassland. 2. Our results demonstrated that the biomasses or abundances of
most components of the two below-ground communities (microbes and
nematodes) were negatively affected by PFG loss and were positively
related to above-ground plant biomass. The removal of dominant PFGs
(perennial bunchgrasses and perennial rhizomatous grasses) reduced the
biomass or abundance of below-ground community components while removal of
less dominant PFGs (perennial forbs and annuals/biennials) did not change
or increased the biomass or abundance of below-ground community
components. 3. The biomass-based ratio of fungal to bacterial microbes and
the number-based ratio of fungal-feeding to bacterial-feeding nematodes
decreased with increasing PFG losses. Variation partitioning analyses
showed that the identity of PFGs together with above-ground plant biomass
explained most of the total variation in soil microbes and that the
identity of PFGs and above-ground plant biomass together with nematode
food resources explained most of the total variation in soil nematodes.
The increase in NEE with PFG loss was mainly explained by decreases in
above-ground plant biomass and the ratio of fungi to bacteria. 4.
Synthesis. The shift of below-ground communities from a fungal-based to a
bacterial-based energy channel as PFG richness decreases indicates that
less diverse grassland ecosystems will have lower nutrient retention and
hence be more sensitive to land use or climate change. The dominant
effects of above-ground plant biomass and below-ground communities on NEE
indicate that PFG loss resulting from land use or climate change has the
potential to reduce C sequestration in semi-arid grassland soils. These
findings suggest that predictive models may need to consider the
composition of above-ground and below-ground communities in order to
accurately simulate the dynamics of CO2 fluxes in terrestrial ecosystems.