Sympatric soil biota mitigate a warmer-drier climate for Bouteloua gracilis

Climate change is altering temperature and precipitation, resulting in
widespread plant mortality and shifts in plant distributions. Plants
growing in soil types with low water holding capacity may experience
intensified effects of reduced water availability as a result of climate
change. Furthermore, complex biotic interactions between plants and soil
organisms may mitigate or exacerbate the effects of climate change. This
three-year field experiment observed the performance of Bouteloua gracilis
ecotypes that were transplanted across an environmental gradient with
either sympatric soil from the seed source location or allopatric soil
from the location that plants were transplanted into. We also inoculated
plants with either sympatric or allopatric soil biotic communities to
test: 1) how changes in climate alone influence plant growth, 2) how soil
types interact with climate to influence plant growth, and 3) the role of
soil biota in mitigating plant migration to novel environments. As
expected, plants moved to cooler-wetter sites exhibited enhanced growth;
however, plants moved to warmer-drier sites responded variably depending
on the provenance of their soil and inoculum. Soil and inoculum provenance
had little influence on the performance of plants moved to cooler-wetter
sites, but at warmer-drier sites they were important predictors of plant
biomass, seed set and specific leaf area. Specifically, transplants
inoculated with their sympatric soil biota and grown in their sympatric
soil were as large or larger than reference plants grown at the seed
source locations, however, individuals inoculated with allopatric soil
biota were smaller than reference site individuals at warmer, drier sites.
These findings demonstrate complicated plant responses to various aspects
of environmental novelty where communities of soil organisms may help
ameliorate stress. The belowground microbiome of plants should be
considered to more accurately predict the responses of vegetation to
climate change.