Changes in community dynamics triggered by declines in precipitation are expected to affect ecosystem function and stability. A better understanding of the impact of declines in precipitation on the herbaceous community composition and structure will help explain changes in the distribution of global savannas and predict their responses to future declines in precipitation. 

In a recent issue of Journal of Vegetation Science, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) reported that precipitation reduction changed the composition and structure of the herbaceous community of Yuanjiang savanna. 

The researchers used a four‐year (2014‐2017) precipitation manipulation experiment to examine changes in herbaceous community composition and structure across the species, functional group and community levels under precipitation reduction. 

They found that precipitation reduction significantly decreased the average height and percentage cover of the herbaceous community, while increasing species richness and the Pielou evenness index. 

The declines of rainfall also significantly decreased average height, percentage cover and relative abundance of graminoids and perennials, but increased those of forbs and annuals. 

Furthermore, most changes in plant traits and herbaceous community processes in response to declines in precipitation were asynchronous on the species and plant functional group levels. 

"Our study provides strong evidence for the existence of very low threshold for changes in herbaceous community structure and composition under varying precipitation treatments, which suggested that the herbaceous community responses to precipitation reduction were essentially nonlinear", said Dr. SONG Qinghai, principal investigator of the study.