Soil nematode community dynamics and drivers along a 30-year post-fire chronosequence in subtropical mixed evergreen-deciduous broadleaf forests

Fire acts as a pivotal ecological engineer that promotes ecosystem renewal while fundamentally reshaping soil biota. Despite its ecological importance, the decadal-scale recovery trajectories of soil nematode communities following fire disturbances remain poorly understood. We quantified the 30-year post-fire dynamics of soil nematodes using a chronosequence spanning 1, 2, 3, 8, 10, 20, and 30 years after fire, along with unburned controls, in subtropical mixed evergreen-deciduous broadleaf forests. Key findings reveal that: (1) Soil nematode community abundance and genus richness demonstrated notable resilience, returning to pre-fire levels throughout the successional process; (2) Bacterivore populations increased by 63.3% within the first year after fire before declining to baseline levels by the end of the decade, whereas fungivores decreased by 26.4% initially but recovered to 92% of control levels within eight years; (3) The nematode channel ratio shifted decisively from bacterial-dominated to fungal-mediated decomposition, indicating a lasting functional reorganization of the soil food web; (4) Structural equation modeling identified soil temperature, pH, and shrub cover as primary drivers of community assembly. Our study offers novel empirical insights into the phased recovery dynamics of forest ecosystems after fire disturbances.