氮添加加剧了海南岛尖峰岭热带山地雨林次生林植物生长的磷限制OA北大核心CSTPCD

Human activities have changed soil nitrogen(N)and phosphorus(P)availability,which potentially affects ecosystem nutrient cycling.To explore nutrient limitation status of different forest types,we evaluated the response of soil and foliar N and P contents to N and P addition in an 11-year continuous fertilization experiment in both primary and secondary montane rainforests.We found that(1)N addition did not affect soil and foliar N and P contents in both primary and secondary forests.In contrast,P addition significantly increased soil available P contents but had no effect on foliar N and P contents in both forests.(2)Foliar N∶P ratios were higher than 16 in CK treatment of both forests.Foliar N∶P significantly decreased after P and NP additions in both forests.N addi-tion significantly increased foliar N∶P of the secondary forest,but not in the primary forest.(3)Soil available N was significantly correlated with available P in the secondary forest,but not in the primary forest.In contrast,there was a significant negative correlation between foliar N∶P and soil available P in both forests.In summary,our findings indicate that P is the limiting factor for plant growth in tropical mountain rainforests.P addition could effec-tively alleviate P limitation.In addition,N addition aggravated P limitation in the secondary forest but not in the primary forest.This study provides an important reference for understanding nutrient limitation pattern of ecosystems in the context of global change.