Taxonomic assembly and trait partitioning contribute comparably to soil invertebrate functional diversity along secondary succession in high-elevation plateau ecosystems

Deforested and abandoned lands have undergone extensive secondary succession. However, the emergence of functional diversity in soil invertebrate communities along the succession, particularly the relative roles of taxonomic assembly and trait partitioning in driving it, remains unclear. To address this issue, we developed a novel “taxonomic diversity-functional distance” analytical approach and applied it to soil invertebrate communities across a high-elevation secondary successional gradient, including secondary grassland, shrubland, arboreal forest, and primary (climax) forest. We found that soil invertebrate functional α diversity (functional richness within plots) increased overall with succession, although it fluctuated with tree identity in the arboreal forest stage. Functional β diversity (functional dissimilarity among plots) declined over succession, supporting the convergent successional model. Both taxonomic α/β diversity (taxonomic richness/dissimilarity) and functional α/β distance (trait partitions within/among plots) jointly shaped observed functional α/β diversity, with comparable contributions. The litter and soil microhabitats shaped functional diversity via taxonomic diversity and trait partitioning, thereby supporting soil multifunctionality succession. Our results advance trait-based soil invertebrate ecology by identifying dual recovery pathways for invertebrate functionality. They highlight trait partitioning as a mechanistic complement to taxonomic assembly, with both making comparable contributions to driving soil ecosystem functioning. Extending tests of these mechanisms across biomes and spatial scales will inform targeted ecosystem management, enhancing the functional benefits of soil biology conservation in global restoration.