Sumei Liu

Soil bacteria, fungi and nematodes are three of the most abundant groups in the belowground micro-food web, yet how they change together during forest recovery after disturbance remains poorly understood. We examined a temperate forest secondary successional sequence in northeastern China, measuring soil nutrients and the diversity, taxonomic composition and functional composition of the three groups, and used structural equation modelling to test how their linking network changes among successional stages. Nutrients did not accumulate uniformly. Available potassium increased stage by stage, carbon and nitrogen fluctuated without a clear trend, and phosphorus peaked at the poplar stage. The diversity of each group tracked a characteristic nutrient most closely, potassium for fungi, nitrogen for nematodes, and carbon broadly for both microbial groups. Taxonomic and functional responses were decoupled. Bacterial and fungal communities diverged strongly among stages, while nematode taxonomic composition stayed largely unchanged, yet nematode feeding composition shifted markedly and fungivorous nematodes reached their highest share at the intermediate broadleaf stage. The pathway network linking nutrients, microorganisms and nematodes kept the same structure in all four stages, so succession changed the strength of these associations rather than the pathways themselves. For soil nematodes, recovery therefore reshapes what the community consumes rather than which taxa it contains, and feeding traits rather than taxonomic counts better capture how the nematode community tracks forest recovery.