Alpine Grassland Ecological Restoration Approaches Shape Insect Trophic Guild Diversity: A Multi-Dimensional Assessment from Alpha to Dark Diversity

The severe degradation of alpine grasslands on the Qinghai-Tibet Plateau poses a significant threat to regional ecological security. While insects are critical for ecosystem functions, their responses to restoration measures in these fragile habitats are poorly documented. This study assessed the initial impacts of four restoration approaches-grazing exclusion fencing (FE), no-till reseeding (FR), planting grass (GC), and grazing control (CK)-on insect trophic guilds (herbivores, predators, saprophagous, and omnivores) in the Qilian Mountains. Using a multi-dimensional indicator (alpha, zeta, and dark diversity), we systematically assessed community assembly and recovery potential. The results revealed the following: (1) FE supported the highest insect abundance, dominated by phytophagous insects. FR significantly enhanced species' richness and diversity across multiple functional groups (<i>p</i> < 0.05). GC significantly increased the richness of omnivorous insects, but caused a significant decrease in the Shannon-Wiener index for saprophagous insects (<i>p</i> < 0.05). (2) Zeta diversity revealed stable, widespread-species-dominated communities under FR and FE, while CK and GC favored rare-species-driven succession. Dark diversity analysis indicated high recovery potential for phytophagous insects under FR and FE, while GC enhanced saprophagous latent diversity. However, we emphasize that mechanistic interpretations require further validation. Our findings highlight no-till reseeding as a promising initial strategy, though longer-term studies are essential to evaluate successional trajectories and establish definitive management protocols for alpine grassland restoration.