Fire rather than nitrogen addition affects understory plant communities in the short term in a coniferous-broadleaf mixed forest

Abstract

Increasing fire risk and atmospheric nitrogen (N) deposition have the potential toalter plant community structure and composition, with consequent impacts on biodiversity and ecosystem functioning. This study was conducted to examine short-termresponses of understory plant community to burning and N addition in a coniferousbroadleaved mixed forest of the subtropical-temperate transition zone in CentralChina. The experiment used a pair-nested design, with four treatments (control,burning, N addition, and burning plus N addition) and five replicates. Species richness, cover, and density of woody and herbaceous plants were monitored for 3 yearsafter a low-severity fire in the spring of 2014. Burning, but not N addition, significantly stimulated the cover (+15.2%, absolute change) and density (+62.8%) of woodyspecies as well as herb richness (+1.2 species/m2, absolute change), cover (+25.5%,absolute change), and density (+602.4%) across the seven sampling dates from June2014 to October 2016. Light availability, soil temperature, and prefire communitycomposition could be primarily responsible for the understory community recoveryafter the low-severity fire. The observations suggest that light availability and soiltemperature are more important than nutrients in structuring understory plant community in the mixed forest of the subtropical-temperate transition zone in CentralChina. Legacy woody and herb species dominated the understory vegetation overthe 3 years after fire, indicating strong resistance and resilience of forest understoryplant community and biodiversity to abrupt environmental perturbation.