Natural Regeneration Outperforms Active Restoration in Enhancing Biodiversity and Biomass Along an Altitudinal Gradient in Chinese Savanna Ecosystems 中国稀树灌草丛中自然恢复对生物多样性与生物量的提升效应优于人工恢复

Abstract

The decline in biodiversity and the reduction of carbon sinks resulting from ecosystem degradation have emerged as significant global challenges. The impact of passive and active restoration on biodiversity and carbon sinks has been well studied across biomes, but remains understudied in degraded savannas, especially regarding long-term outcomes. This study examines how species composition, biodiversity, and biomass accumulation in herbaceous communities respond to different restoration strategies across an altitudinal gradient in the degraded savannas of southwestern China. Fenced reserves significantly increased average height, cover, diversity, and biomass of herbaceous communities across elevation gradients, with a shift in species dominance toward Eulaliopsis binata. Acacia confusa forest increased herbaceous cover at low elevations and enhanced diversity across the gradient, whereas Leucaena leucocephala forest increased cover at high elevations but consistently reduced diversity at all elevations, leading to a single-species dominance. Both active restoration treatments resulted in lower herbaceous biomass compared to natural regeneration (fenced reserves). These results suggest that natural regeneration more effectively supports both biodiversity and biomass accumulation across elevation zones, while active restoration exhibits altitude-dependent efficacy and limited biomass accumulation capacity. This study provides a foundation for selecting context-appropriate restoration approaches to enhance biodiversity and carbon storage, and supports the optimization of ecological restoration strategies and forest management practices in savanna ecosystems.