城郊梯度上南亚热带季风常绿阔叶林土壤C、N、P化学计量特征

Stoichiometric characteristics of soil C,N and P in subtropical forests along an urban-tosuburb gradient

随着城市化进程加剧,人们越来越关注城市森林生态系统的结构与功能。森林土壤碳（C）、氮（N）、磷（P）化学计量变化对于理解森林生态系统结构和功能的稳定性具有重要意义。本文以高度城市化的珠江三角洲城-郊梯度上亚热带常绿阔叶林为研究对象,分析城区、郊区梯度上土壤C、N、P的化学计量特征。结果表明：郊区森林表层（0~10 cm）和亚表层（10~20 cm）土壤C、N含量均显著高于城区（P〈0.001）;城区森林表层土壤P含量与郊区差异不显著（P=0.226）,而郊区森林10~20 cm土层土壤P含量显著高于城区（P=0.001）。城区森林土壤N∶P和C∶P均高于郊区,而城区森林土壤C∶N与郊区差异不显著。快速的城市化使南亚热带森林土壤营养元素循环发生改变,降低了城市森林生态系统结构与功能的稳定性。

With increasing urbanization,more and more attention has been paid on the structure and functions of urban forests. The changes in ecosystem structure and function can be reflected by those in stoichiometric characteristics of carbon（ C）,nitrogen（ N） and phosphorus（ P）. In order to explore potential influences of urbanization on the stoichiometric characteristics of C,N and P,soil samples（ 0-10 and 10-20 cm） were collected from six subtropical forests along an urban-to-suburb gradient in the Pearl River Delta that has been experiencing an unprecedented level of urbanization. The results showed that soil C and N concentrations in layers 0-10 cm and10-20 cm were significantly higher in the suburb forests than in the urban forests. There was no significant difference in soil P concentrations in 0-10 cm layer between the urban and suburb forests（ P = 0.226）. However,soil P concentrations in 10-20 cm were significantly greater in the suburb forests than in the urban forests（ P = 0.001）. Both soil N ∶ P and C ∶ P were significantly higher in the urban forests than in the suburb forests but soil C ∶ N was not significantly different.Our results suggested that rapid urbanization changed nutrient cycling in subtropical forests,which would reduce the stability of structure and function of urban forests.