Effects of altered precipitation on insect community composition and structure in a meadow steppe

Abstract

Precipitation can be a key driver of ecosystem functioning in semi‐arid and arid grasslands. Altered precipitation patterns had significant impacts on plant community dynamics, which in turn influenced the community composition and structure of higher trophic levels, especially insects, in grasslands. A field experiment was conducted by manipulating the amount of natural precipitation (control, +30% rainfall, and −30% rainfall) to examine the effects of altered precipitation patterns on insect diversity, abundance, and trophic structure in a meadow steppe over 3 years (2007–2009). The results showed that the increased precipitation treatment significantly enhanced above‐ground biomass of the entire plant community and particularly grasses, whereas the decreased precipitation treatment significantly reduced them. There were year‐to‐year changes in species richness, Shannon–Wiener index, and abundance of the whole insect community. Both increased and decreased precipitation caused declines in insect species richness and abundance owing to potentially complex vegetation‐mediated effects and direct habitat effects. The abundance of each trophic guild in the insect community responded differently to altered precipitation patterns, with lower herbivore abundance and unchanged abundance of predators and parasitoids. Thus changes in precipitation may generate an insect community that is increasingly dominated by secondary consumers. The present results suggest that altered precipitation causes a declines in insect diversity and shifts in trophic structure, potentially influencing ecosystem functioning in grasslands. Additionally, the inter‐annual variation in the insect community under altered precipitation highlights the importance of long‐term experiments for drawing correct conclusions about the impacts of climate change on grassland ecosystems.