[Species-habitat association of a deciduous broadleaved forest in the subtropical and tempe-rate transition zone]. / 亚热带-温带气候过渡区落叶阔叶林物种-ç”Ÿå¢ƒå ³è”åˆ†æž.

The species-habitat association analysis facilitates a better understanding of species coexis-tence and community assembly. Here, all trees in a 25-hm2 broadleaved deciduous forest plot in the Qinling Mountains of North-central China were classified into three life stages (i.e., seedling, sapling, and adult). The Torus-translation test was used to examine the species-habitat association. The results showed that the association of species with habitats varied across different species. Most species were significantly associated with high slopes, 95.7% of which showed negative association. 89.5% and 90.9% of tree species were negatively associated with low slopes and ridges, respectively. Most species had positive association with high valley, with only one negative association (0.03%). There were 80, 44 and 23 significant associations with habitats at seedling, sapling and adult stages, respectively, indicating that a greater dependence of seedlings on habitat. 38 species at seedling stage and 25 species at the sapling stage were associated with at least one habitat type, while only 17 species at the adult stage were significantly associated. The effects of habitat on species varied across life stages, showing a weaker species-habitat association at the later stage. Due to the specific environmental demands, most species showed different habitat preferences across life stages.

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

Increasing fire risk and atmospheric nitrogen (N) deposition have the potential to alter plant community structure and composition, with consequent impacts on biodiversity and ecosystem functioning. This study was conducted to examine short-term responses of understory plant community to burning and N addition in a coniferous-broadleaved mixed forest of the subtropical-temperate transition zone in Central China. 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 years after 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 woody species 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 June 2014 to October 2016. Light availability, soil temperature, and prefire community composition could be primarily responsible for the understory community recovery after the low-severity fire. The observations suggest that light availability and soil temperature are more important than nutrients in structuring understory plant community in the mixed forest of the subtropical-temperate transition zone in Central China. Legacy woody and herb species dominated the understory vegetation over the 3 years after fire, indicating strong resistance and resilience of forest understory plant community and biodiversity to abrupt environmental perturbation.