In our country, grassland is one of important ecosystem and is an important ecological barrier, and green animal husbandry production base. The ecosystem plays an important role in maintaining national ecological security, food security and even global ecological balance.  

However, climate change is expected to lead to more frequent extreme droughts in this region. Thus, it is critical to understand the mechanisms for how these valuable ecosystems will respond to such climate extremes. Yet, the underlying mechanisms of ecosystem responses to drought are not well understood in grasslands. 

So, a research team from Institute of Applied Ecology of Chinese Academy of Sciences addressed this issue by experimentally removing 66% of growing season precipitation for four years in two grasslands of Inner Mongolia. 

As expected, the researchers found that these two sites differed markedly in their aboveground net primary productivity (ANPP) responses to soil moisture, with greater sensitivity at the more arid site. The researchers used structural equation modeling to further examine the underlying community-based mechanisms for such differential ANPP responses to declining soil moisture. Surprisingly, the results indicated very little influence of species richness on ecosystem responses to drought. However, ANPP responses to drought were indirectly mediated by community functional composition (i.e. community-weighted traits and functional diversity) as well as soil nutrient availability. Moreover, these indirect effects differed by site with stronger buffering influences observed at the site with greater ecosystem drought resistance.  

Together, these results highlight the importance of understanding the unique indirect effects of drought on semi-arid plant communities. These results have broad impacts for improving models of ecosystem sensitivity to drought with climate change.  

Relevant results were published online in the journal Ecology with the title of “Plant traits and soil fertility mediate productivity losses under extreme drought in C₃ grasslands”. 

Fig.1 Best-fit structural equation modeling relating ANPP to soil recourse availability and several indices of community composition for (a) the Hulunber and (b) Xilingol sites as well as (c) both sites together in Northern China. Numbers adjacent to arrows are standardized path coefficients. Continuous and dashed arrows indicate significant (^P<0.1; *P< 0.05, **P< 0.01, and ***P< 0.001) positive and negative pathways, respectively. Black and gray arrows indicated significant and non-significant pathways, respectively. Conditional R² denotes the proportion of variance explained (Image by LUO Wentao).