Global climate change is expected to increase rainfall variability, potentially increasing the frequency of extreme droughts during this century. Intensified drought will affect ecosystem functioning, with many ecosystems expected to experience reductions in primary productivity. The effects of extreme drought on plant community structure and function not only exist during extreme drought events, but also may produce legacy effects that continue to influence grassland ecosystem function and its response to environmental change. Thus, a better understanding of recovery mechanisms is critical for predicting the future dynamics of terrestrial ecosystems.

To address this knowledge gap, a research team from the Institute of Applied Ecology of the Chinese Academy of Sciences conducted a four-year extreme drought followed by a three-year recovery period to study the effects of drought and recovery on aboveground net primary productivity (ANPP) in a grassland in northern China. Surprisingly, they found that ANPP in the drought-plots recovered to the level of the control-plots within one year after extreme drought.  

The researchers further investigated the mechanisms that maintain the recovery of ANPP after extreme drought based on the dynamics of underground bud banks.

According to the researchers, long-term drought reduced the ANPP of grasses and forbs, as well as total ANPP, which alleviated the pressures of resource competition and opened up certain niches.

In addition, the underground bud bank of grasses was well stocked and quickly tilled after the drought, which effectively supplemented the aboveground population, occupied the ecological niche space, and promoted the grass recovery. 

In contrast, the bud banks of forbs did not recover after extreme drought. The aboveground population was insufficient and regeneration was limited, resulting in the decline of forb ANPP during the recovery period. These results would be helpful to better understand the mechanisms underlying the drought effects on grassland structure and function in northern China. 

Relevant results have been published in Journal of Ecology entitled "Compensatory dynamics drive grassland recovery from drought." 

The responses of grassland to drought and recovery. (Image by LUO Wentao)