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

Nitrogen addition exacerbated phosphorus limitation of plant growth in a secondary tropical montane rain-forest of Hainan

人类活动改变了生态系统中氮(N)和磷(P)的有效性,正深刻影响着生态系统的养分循环。本研究以海南尖峰岭热带山地雨林原始林和次生林为对象,通过11年野外氮(N)、磷(P)和氮+磷(NP)添加实验,量化氮、磷添加对土壤和植物叶片N、P含量的影响,探讨热带森林的养分限制格局。结果表明:N添加对原始林和次生林土壤和叶片N、P含量均无显著影响;P和NP添加显著提高了原始林和次生林土壤有效P含量,而对叶片N、P含量无显著影响;自然条件下原始林和次生林叶片N∶P均超过16,P与NP添加均显著降低了两种林型叶片N∶P;N添加显著增加了次生林叶片N∶P,而对原始林叶片N∶P影响不显著;次生林中土壤有效N和土壤有效P呈显著负相关,原始林中两者关系不显著,而两种林型中叶片N∶P均与土壤有效P呈显著负相关。上述研究结果表明:尖峰岭热带山地雨林原始林和次生林植物生长均受P限制,P添加可以有效缓解P限制;N添加加剧了热带山地雨林次生林的P限制作用。该研究为增进全球变化背景下的生态系统养分限制格局的了解提供重要的参考依据。

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.