Department of Ecology, College of Urban and Environmental Sciences, Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing 100871, China.
Department of Ecology, College of Urban and Environmental Sciences, Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing 100871, China.
Sci Total Environ. 2018 Mar 15;618:1064-1070. doi: 10.1016/j.scitotenv.2017.09.099. Epub 2017 Nov 7.
Rapid increase of global nitrogen (N) deposition has greatly altered carbon cycles and functioning of forest ecosystems. Previous studies have focused on changes in carbon dynamics of temperate and subtropical forests through N enrichment experiments; however, the effects of N deposition on tree growth remain inconsistent, especially in tropical forests. Here, we conducted a five-year N addition experiment (0 and 50kgNhayr) in a tropical montane rain forest in Hainan Island, China, to explore the effects of enhanced N deposition on growth of trees. We also set phosphorus (P) treatment (50kgPhayr) and N+P treatment (50kgNhayr+50kgPhayr) to examine potential P limitation driven by N deposition. Our results showed that N addition has not significantly influenced tree growth, while P addition significantly increased the relative growth rate of small (diameter at breast height, DBH≤10cm) and medium (10<DBH≤20cm) trees. The combined N and P addition accelerated the growth of small trees, but did not affect the growth of medium and large (20cm<DBH) trees. These contrasting effects of N and P addition on tree growth indicate that the tropical montane forest is mainly limited by P, which suggests the importance of P in regulating growth of trees in tropical forests.
全球氮（N）沉积的快速增加极大地改变了碳循环和森林生态系统的功能。先前的研究主要集中在通过 N 富集实验研究温带和亚热带森林的碳动态变化；然而，N 沉积对树木生长的影响仍然不一致，特别是在热带森林中。在这里，我们在中国海南岛的一个热带山地雨林中进行了为期五年的 N 加富实验（0 和 50kgNhayr），以探讨增强的 N 沉积对树木生长的影响。我们还设置了磷（P）处理（50kgPhayr）和 N+P 处理（50kgNhayr+50kgPhayr），以检验由 N 沉积驱动的潜在 P 限制。我们的结果表明，N 加富并没有显著影响树木的生长，而 P 加富显著增加了小（胸径，DBH≤10cm）和中（10<DBH≤20cm）树木的相对生长率。N 和 P 的联合添加加速了小树的生长，但对中树和大树（20cm<DBH）的生长没有影响。N 和 P 添加对树木生长的这种相反影响表明，热带山地森林主要受 P 限制，这表明 P 在调节热带森林中树木生长方面的重要性。
