This study is a global meta-analysis of the effects of grassland plant
species richness on aboveground and belowground carbon and nitrogen
dynamics. Observations from 73 studies in grasslands totaling 1385
paired observations of plant mixtures and monocultures were compiled.
Response variables included nine carbon and six nitrogen processes to
plant diversity, examined the effects of experimental types and age on
the responses, and predicted the carbon and nitrogen balance following
different biodiversity loss scenario in grasslands. We found that carbon
and nitrogen functions significantly enhanced in plant mixtures, but
varied with experimental types. Most of the attributes was significantly
correlated with species richness and experimental age, the relationship
between species richness and carbon and nitrogen processes was
interacted with experimental duration in the field experiments, except
for soil respiration, fungal biomass, and soil nitrate nitrogen.
Importantly, our results showed that the declines in soil carbon and
nitrogen pool accelerated following plant diversity loss. Our
meta-analysis revealed that the plant diversity has ubiquitous impacts
on carbon and nitrogen cycles in grasslands, likely driven by
complementarity effects of plant diversity on plant productivity and
biomass, underlined interactive effects of plant diversity, experimental
types and age, and climate on carbon and nitrogen processes, and
suggested that the reduction in carbon and nitrogen stocks in grasslands
will be larger following biodiversity loss in the future.