为了解同一生活型不同种植物叶片碳(C)、氮(N)、磷(P)生态化学计量学特征随季节变化的响应规律, 在生长季不同月份, 对阿拉善荒漠区6种主要灌木植物霸王(Zygophyllum xanthoxylum)、白刺(Nitraria tangutorum)、红砂(Reaumuria soongorica)、驼绒藜(Ceratoides latens)、猫头刺(Oxytropis aciphylla)、沙冬青(Ammopiptanthus mongolicus)的物候期进行了连续的观察, 并采集植物叶片, 分析了其C、N、P含量及计量比在不同月份的变化。结果显示: 1)同一生活型的6种植物的叶片C、N、P及C:N、C:P和N:P在整个生长季内的变化规律不同, 且以上各指标季节间的变异系数在6种植物之间也存在差异; 2)单个植物种叶片C、N、P含量及其计量比的季节变异分析显示, 叶片C、N含量及C:N的季节变异较小, 叶片P含量及C:P和N:P的季节变异较大, 6种植物叶片C、N含量及C:N由于季节变异所计算的变异系数变化范围分别为0.60%-10.20%、6.09%-20.50%和5.87%-18.78%, 6种植物叶片P含量的季节变异所产生的变异系数范围为16.43%-43.43%, 叶片C:P和N:P的变异系数范围分别为8.48%-31.95%和11.86%-40.73%; 3)综合分析6种植物叶片C、N、P及其计量比各指标在整个生长季节内的变异, 变异系数由大到小排序为: P (28.85%) > C:P (25.02%) > N:P (22.18%) > N (14.22%) > C:N (12.48%) > C (4.62%); 4) 生长季节与植物种类对植物叶片C、N、P及其计量比影响的交叉分析显示, 植物叶片C、N含量的变异主要受植物种类影响, 植物叶片P含量的变异主要受生长季节影响, 植物叶片C:N、C:P和N:P的变异都主要受植物种类影响。

Aims Our objective was to explore seasonal variations of leaf C:N:P stoichiometry in plants with the same growth form.
Methods We chose six shrubs in the desert of the Alxa Plateau in north-central China (Zygophyllum xanthoxylum, Nitraria tangutorum, Reaumuria soongorica, Ceratoides lateens, Oxytropis aciphylla and Ammopiptanthus mongolicus) and observed their phenological stages from May to October 2010. Leaf samples were collected during this period, and leaf C, N and P contents and C:N:P stoichiometry were monitored.
Important findings Seasonal dynamics of leaf C, N and P contents and C:N, C:P and N:P mass ratio in the six shrubs were species-specifics, and the variation of leaf C, N and P and C:N, C:P and N:P mass ratios in different species were also dramatically different. Based on variation analysis among different seasons within species, there were less seasonal dynamics in C and N contents and C:N mass ratio than the other three parameters including P contents and C:P and N:P mass ratios. The range of values of coefficient of variation (CV) for C and N contents and N:P mass ratio was 0.60%-10.20%, 6.09%-20.50% and 5.87%-18.78%, respectively. For the other three parameters, the range of CV values for P content was 16.43%-43.43%, and C:P and N:P mass ratios were 8.48%-31.95% and 11.86%-40.73%, respectively. With the comprehensive analysis based on the total variation (resulting from two factors: season and species) for each parameter in these six shrubs, the rank of CV for each parameter was P (28.85%) > C:P (25.02%) > N:P (22.18%) > N (14.22%) > C:N (12.48%) > C (4.62%). Factorial analysis of variation for each parameter, with sampling date (season) and species as independent variables, showed that leaf C and N contents and leaf C:N, C:P and N:P mass ratios were mainly determined by plant species. For leaf P contents, it was the sampling date (season).