Negative impacts of plant diversity loss on carbon sequestration exacerbate over time in grasslands

Positive relationships between plant
species diversity and carbon attributes have been observed in grasslands, but synthesis
studies of how plant diversity affects the carbon balance of grasslands and how
the response ratio changes over time both remain limited. By conducting a
global meta-analysis with 811 paired observations of plant mixtures and
monocultures from 83 studies in natural and manipulated grasslands, we
investigated the impacts of plant diversity on six carbon attributes, its
interaction with experimental duration, and the changes in carbon balance under
different plant diversity loss scenarios in the future. We found that the aboveground
biomass (AGB), belowground biomass (BGB), total biomass (TB), soil organic
carbon (SOC), soil respiration (Rs), and heterotrophic respiration (Rh) significantly
increased in the plant mixtures, and the response ratio for all carbon
attributes increased logarithmically with species richness. We also found that the
response ratio for all carbon attributes except Rs increased linearly with
experimental duration. The increase in response ratio of AGB, BGB, TB, and SOC with
species richness was more pronounced with the long-term experimental duration.
Importantly, our results showed that the
declines in carbon sequestration will be exacerbated by different plant
diversity loss scenarios in the future. Our
meta-analysis revealed that plant diversity loss has ubiquitous negative impacts
on multiple carbon attributes in grasslands, underlined the interactive effects
of plant diversity loss and experimental duration on carbon attributes, and suggested
that the reduction of carbon storage in grasslands following biodiversity loss will
be greater in the future.