Species Diversity and Stability of Dominant Species Dominate the Stability of Community Biomass in an Alpine Meadow Under Variable Precipitation

The stability of aboveground net primary productivity (ANPP) is critical for ecosystem functions and services, and have been studied across a wide range of ecosystems. An intriguing and challenging question emerging from these studies is how precipitation fluctuations, especially extreme precipitation, affect the temporal stability of ANPP in alpine meadow. We investigated the changes in plant community composition and aboveground biomass in an alpine meadow over six consecutive years under five precipitation treatments (increase of 50%, natural precipitation, decreases of 30%, 50% and 90%) in order to reveal the response of ANPP stability to the precipitation change, especially extreme precipitation, and the relevant driving mechanisms. The alpha diversity of plant species did not differ significantly among the treatments. ANPP was resistant to changes in precipitation between 354 and 1336 mm (precipitation interval of 50% decrease in precipitation in the driest year and 50% increase in precipitation in the wettest year during the experiment), suggesting that normal interannual fluctuations in precipitation and recent changes in regional precipitation might not significantly influence ANPP stability. However, extreme precipitation treatment (90% decrease), significantly reduced ANPP, species asynchrony and ANPP stability. A path model indicated that ANPP stability was directly affected by population stability, species asynchrony and grass stability. While the effect of species diversity on ANPP stability depends on the extents to which it positively affects species asynchrony and negatively affects population stability. In addition, the dominant species stability did not directly affect ANPP stability, while indirectly affected ANPP stability by changing the asynchrony of species.