Elevation-dependent effects of early snowmelt on species and functional diversity in Himalayan alpine plant communities

Snow-melt timing is a strong environment filter and determinant of plant community composition and structure in alpine regions. Under the projected climate change scenarios, increasing temperatures and declining snowfall are likely to cause early snow-melting (ES) conditions. Previous biodiversity experiments have shown significant alteration in plant functional traits and species diversity (SD) due to ES. However, realistic evidence is still required to understand how functional diversity (FD) in alpine communities would respond to ES. So, we conducted a 3-year ES experiment along elevation gradient (3550–4450 m) in Western Himalaya to investigate the effect of ES on SD and FD. We found that ES conditions can lead to an increase in SD, community weighted means of leaf area, plant height, leaf nitrogen content, FD indices, soil nitrogen content and organic matter, with more pronounced effects at upper elevations. Variation partitioning analysis revealed that both ES treatment and soil characteristics independently and interactively structured alpine plant community composition and functional traits. These findings suggest that, due to changes in species composition and their abiotic environment under ES conditions, future Himalayan alpine plant communities are expected to transition towards species with greater height, increased leaf size and faster resource acquisition abilities. Our findings demonstrate that, ES acts as a key determinant of community assembly and functional trait composition in alpine ecosystems, with trait-mediated reassembly processes likely to cascade through ecosystem structure and function in a rapidly warming world.