华北落叶松根茎叶碳氮磷含量及其化学计量学特征的季节变化

以秦岭20年生华北落叶松(Larix principis-rupprechtii)人工林为研究对象, 对其不同季节细根、茎(干)和针叶中的碳(C)、氮(N)、磷(P)含量以及生态化学计量学特征进行了分析。结果表明, 根、茎和叶中C含量在生长季节内呈先升高再降低而后又升高的变化趋势, 3种器官C含量从大到小依次为茎>针叶>细根; N含量呈波动式变化; 针叶和细根中P含量均呈“降低→升高→降低→相对稳定”的变化趋势, 茎中P含量则呈先降低后升高又逐渐降低的变化趋势, N和P含量均依次为针叶>细根>茎。在华北落叶松整个生长季(5–10月), 细根和针叶中均为全N含量变异性最大, 茎中则为P含量的变异系数最大, 3种器官中C含量的变异性均最小。华北落叶松3种器官中C:N和C:P的季节变化趋势与各器官N、P含量的变化规律相反。N:P值在茎中最高, 在细根中最低。整个生长季中C:N的变异系数从小到大依次为细根<茎<针叶, 而C:P和N:P的变异系数从小到大的排序均为细根<针叶<茎。生长季节与不同器官对华北落叶松C、N、P含量及其计量比影响的交叉分析显示, C、N和P含量及C:N的变异主要受不同器官的影响, C:P和N:P的变异则主要受不同器官和生长季节的交互作用影响。细根C:N:P质量比(369:7:1)与针叶(309:10:1)相近。细根C、N和P的生态化学计量特征相对稳定, 不受生长季节的影响, 可用于生态系统问题的分析。

Seasonal Variation in Contents of C,N and P and Stoichiometry Characteristics in Fine Roots,Stems and Needles of Larix principis-rupprechtii

We collected 20-year-old Larix principis-rupprechtii from a plantation in Qinling to explore the contents of C, N and P and their ecological stoichiometry characteristics in fine roots, stems and needles in different seasons. The content of C increased first, then decreased and increased again throughout the growing season (May to October). The order of the mean content of C in organs was stems > needles > fine roots. The content of N in fine roots, stems and needles tended to fluctuate during the growing season. The content of P in both needles and fine roots decreased first, then increased and decreased again, then remained stable. The content of P in stems decreased first and then increased, then decreased gradually. The order of the mean content of both N and P in organs was needles > fine roots > stems. The content of N had the greatest variability in fine roots and needles throughout the growing season. The coefficient of variation (cv%) of P was greatest for stems. The variability of C in the 3 organs was the smallest. The changes in C:N and C:P ratios were opposite to that of corresponding N, P content in fine roots, stems and needles. The ratio of N:P peaked in stems and was minimal in fine roots. The order of the cv% for C:N throughout the growing season was fine roots < stems < needles and for both C:P and N:P was fine roots < needles < stems. Factorial analysis of variation for each parameter, with sampling season and organs as independent variables, showed that the content of C, N and P and C:N mass ratio mainly depended on the organ. C:P and N:P mass ratios were mainly determined by the interaction of organs and season. The mass ratio of C:N:P was similar in fine roots (369:7:1) and needles (309:10:1). The characteristics of C, N and P stoichiometry were relatively stable in fine roots. Quantitative characteristics in fine roots were affected less in different seasons in L. principis-rupprechtii in Qinling, which helps in analysis of the ecological system.