三峡库区库首森林生态系统植物叶片碳氮磷化学计量特征研究

【目的】森林是三峡库区重要的生态屏障,研究该地区森林生态系统化学计量特征可深入了解生态系统的养分循环、限制作用以及稳定机制。【方法】通过对三峡库区库首森林生态系统的7个站点进行典型取样,研究了包括乔木、灌木和草本30种植物的107个样品叶片中碳(C)、氮(N)和磷(P)的化学计量学特征。【结果】三峡库区库首森林生态系统植物叶片中有机碳(OC)、全氮(TN)和全磷(TP)的含量变化范围分别为352.0～506.3、8.3～48.6和0.5～2.5 mg/g,平均值为450.2、18.6和1.2 mg/g; 叶片C/N、C/P和N/P的变化范围为7.6～56.5、158.8～799.3和7.3～40.2,平均值为28.6、450.4和16.9。不同生活型植物叶片的养分组成存在显著差异,乔木叶片的有机碳含量要明显高于灌木和草本,而草本植物的叶片全氮和全磷的含量要明显高于乔木和灌木; 落叶乔木叶片的全氮、全磷含量及N/P的值要明显高于常绿乔木,但有机碳含量及C/N和C/P的值则相反。不同生活型植物有机碳与全氮(磷)含量的相互关系也存在差异,草本植物叶片有机碳与全氮(磷)含量存在极显著负相关,乔木叶片有机碳与全氮含量呈显著的负相关,但与全磷含量不相关,灌木叶片有机碳与全氮(磷)含量不相关; 不同生活型植物叶片全氮和全磷含量均存在极显著正相关。【结论】三峡库区库首森林生态系统植物叶片有机碳含量处于中等水平,而全氮和全磷含量相对较低,磷缺乏是限制该区植被生产力的关键元素。

Stoichiometric characteristics of leaf carbon,nitrogen and phosphorus in forest ecosystems in the head of the Three Gorges Reservoir Area

【Objective】 Forests are important ecological barriers for the Three Gorges Reservoir Area. Therefore, a study on the stoichiometric characteristics of forest ecosystems in this area was conducted to provide significant understanding of the nutrient cycle, limiting effects and stabilizing mechanisms of ecosystems. 【Method】 A total of 107 samples from forest ecosystems at seven sites in the head of the Three Gorges Reservoir Area was collected to study the stoichiometric characteristics of carbon(C), nitrogen(N)and phosphorus(P)in leaves of 30 plant species(including trees, shrubs and herbs). 【Result】 The C, N and P contents in leaves varied within the ranges of 352.0-506.3, 8.3-48.6 and 0.5-2.5 mg/g, with the averages of 450.2, 18.6 and 1.2 mg/g, respectively. The ratios of C/N, C/P and N/P in leaves were in the ranges of 7.6-56.5, 158.8-799.3 and 7.3-40.2, with the averages of 28.6, 450.4 and 16.9, respectively. The nutrient compositions differed significantly among the plant types. The C content of leaves was significantly higher in trees than in shrubs and herbs, and the N and P contents in leaves were significantly higher in herbs than in trees and shrubs. Compared with evergreen trees, N and P contents and N/P ratio in the leaves of deciduous trees were significantly high whereas the C content and C/N and C/P ratios were significantly low. The relationships between leaf C and N(P)content also showed significant differences among the plant types. There was a highly significantly, negative correlation between the C and N(P)contents in herb leaves, but C content was significantly negatively correlated to N content, and there was no significant correlation to P content in trees. There was no significant correlation between the C and N(P)contents in shrubs. The N and P contents were significantly, positively correlated in leaves of all plant types. 【Conclusion】 In the forest ecosystems of the head of the Three Gorges Reservoir Area, the C content of leaves was medium, whereas the N and P contents in leaves were relatively lower. Our results suggest that P deficiency is the key limiting element for vegetation productivity.