The effects of short-term warming on plant diversity, productivity, and their relationship in alpine grasslands

Biodiversity and productivity, which are key determinants of ecosystem services, exhibit significant variation under global change. However, the effects of short-term warming on plant community biomass, species diversity, and their relationships (biodiversity-productivity relationship, BPR) in alpine meadows are not well understood. We conducted a continuous three-year warming experiment in an alpine meadow on the Tibetan Plateau using open-top chambers. Our results showed that warming significantly altered community species diversity. One-year warming significantly increased the species richness, Shannon index, and Simpson index in comparison to the control. Three-year warming significantly decreased the species richness compared to the control. This was attributed to the modification of plant community structure by warming, which enhanced species turnover and ultimately resulted in reduced species diversity. A negative relationship between aboveground biomass (AGB) and species turnover was observed under warming conditions. Regression analysis and structural equation modeling (SEM) further confirmed that warming exacerbates the negative influence of species turnover (beta-diversity) on AGB. Meanwhile, the results from random forest analysis and SEM indicated that warming alleviates the negative impact of available nitrogen on the Shannon diversity and AGB. Thus, short-term warming enhanced the species turnover within plant communities, thereby exacerbating the negative influence of beta-diversity on productivity. Concurrently, warming mitigated the limitation imposed by available nitrogen on productivity. Our findings provide key insights into the response of alpine grasslands to short-term warming and help predict the potential impacts of climate change on their ecological functions.