%A Fengmin Huang, Minxia Liang, Yi Zheng, Xubing Liu, Yuxin Chen, Wenbin Li, Shan Luo and Shixiao Yu %T Soil nitrogen availability intensifies negative density-dependent effects in a subtropical forest %0 Journal Article %D 2020 %J J Plant Ecol %R 10.1093/jpe/rtaa012 %P 281-287 %V 13 %N 3 %U {https://www.jpe.ac.cn/CN/abstract/article_60729.shtml} %8 2020-06-01 %X
Aims

The importance of density-dependent mortality in maintaining tree species diversity is widely accepted. However, density-dependent effects may vary in magnitude and direction with different abiotic conditions in forests. Theoretical predictions surmise that density-dependent effects may vary with soil available nitrogen (AN), but this still needs to be tested.

Methods

We analyzed the density-dependent effects on survival of newly germinated seedlings for 18 common species based on a long-term seedling census across environmental gradients in a subtropical forest. We also conducted a root lesion detection experiment for five species to investigate the potential effects of pathogens on variation in density-dependent disease between rich and poor AN environments.

Important Findings

The seedling dynamics analysis revealed that the strength of density-dependent effects increased with AN, shifting from neutral or positive with low AN to negative with high AN. Three of the five tree species had stronger density-dependent effects on root lesions in rich AN environments than in poor AN environments, which is consistent with the results of a long-term seedling dynamics analysis. We also found higher species diversity in rich AN environments, which may be promoted by the stronger negative density-dependent effects. Both the seedling dynamic analysis and root lesion detection experiment revealed stronger negative density-dependent effects in higher AN environment, resulting from stronger disease pressure by soil pathogens. Our study emphasized the importance of considering context dependence when testing the density dependence hypotheses.