华北石质山地侧柏人工林C、N、P生态化学计量特征的季节变化

以北京九龙山自然保护区幼龄侧柏人工林为研究对象,对其不同生长季节叶、枝、根(0—10 cm、10—20 cm土层)的碳(C)、氮(N)、磷(P)含量及其生态化学计量学特征进行了分析,深入探讨了生长季节与器官以及两因素交互作用对以上特征的影响,研究有助于理解植物各性状之间的相互作用以及植物生长过程中资源的利用和分配状况。结果表明:1)不同器官间C含量为414.97—461.58 g/kg,枝最大,根(0—10 cm)最小;N含量为6.57—14.28 g/kg,叶最大,枝最小;P含量为0.39—1.28 g/kg,叶最大,根(10—20 cm)最小;C∶N为31.76—70.98,枝最大,叶最小;C∶P为369.93—1099.20,根(10—20 cm)最大,叶最小;N∶P为9.21—23.81,根(0—10 cm)最大,枝最小。整个生长季节中侧柏各器官C含量最稳定,变异系数均小于7%;P含量变异性最大,变异系数均超过15%,N含量变异性介于两者之间;各器官中C∶N和N∶P较C∶P更为稳定,C、N与P具有较好的耦合协同性,C∶P和N∶P的变化主要取决于P的变化。2)器官对C、N、P含量及其化学计量关系均存在显著影响,生长季节对N和P含量存在显著影响,两者交互作用只对P含量存在显著影响,器官对侧柏C、N、P含量及其化学计量变异的贡献大于生长季节。3)侧柏各器官间C、N、P含量及其化学计量比相关性多数未达到显著性水平,仅有叶与枝中的P及C∶P显著相关,说明侧柏器官分化过程中各器官对元素的吸收利用具有特异性。侧柏叶片N∶P14,说明生长季节里幼龄侧柏人工林更多受到N限制。

Seasonal variation in C, N, and P stoichiometry of Platycladus orientalis plantation in the rocky mountainous areas of North China

This study was conducted to analyze the dynamics of carbon (C), nitrogen (N), and phosphorus (P), and their stoichiometric characteristics in different organs (leaves, branches, and roots) and during different seasons, in a young plantation of Platycladus orientalis in the Beijing Jiulong nature reserve. Studies on these relationship provide insights into interactions among plant functional traits and plant strategies for resource acquisition and mass partitioning. The results showed that branches contained the highest concentration of C but the lowest concentration of N. Leaves had the highest concentrations of N and P, whereas roots possessed the lowest concentration of C and P. Moreover, leaves had the lowest C:N and C:P ratios, whereas roots had the highest ratios of N:P and C:P, and branches had the highest C:N ratio but the lowest N:P ratio. Furthermore, during the growing season, the concentration of C in each organ was more stable than that of N and P. The C:N and N:P ratios in each organ were more stable than the C:P ratio. Both C and N concentration were strongly positively correlated with P concentration, with the change in C:P and N:P ratios being mainly determined by P concentration. Plant organs differed significantly in terms of the concentrations of C, N, and P and the ratios C:N, C:P, and N:P, whereas seasonal factors significantly influenced the concentrations of N and P, but their interaction effect only had influence on the concentration of P. Compared with the seasonal variations, the difference between organs made a larger contribution in determining the concentrations of C, N, and P and their stoichiometry in P. orientalis. The concentrations of C, N, and P and their stoichiometry showed no significant relationships among plant organs, except for the concentration of P and the C:P ratio between leaves and branches, which indicates that the organs have specific requirements for element absorption and utilization during the process of organ differentiation. The recorded leaf N:P ratio less than 14 indicates that the growth of young P. orientalis plants is more restricted by N during the growing seasons.