鄱阳湖沙山单叶蔓荆不同器官碳、氮、磷化学计量特征

C, N and P stoichiometry in different organs of Vitex rotundifolia in a Poyang Lake desertification hill

在鄱阳湖湖滨沙山沿沙化梯度测定了单叶蔓荆(Vitex rotundifolia)花、叶、枝条、匍匐茎、细根的碳(C)、氮(N)、磷(P)含量,以阐明单叶蔓荆各器官C、N、P含量及化学计量比的分配格局,探讨养分元素及其化学计量之间的关联及对沙化程度的响应。结果表明:(1)单叶蔓荆各器官C、N、P含量变化范围分别为386.28–449.47 mg·g^(–1)、11.40–25.37 mg·g^(–1)、0.89–1.54 mg·g^(–1)。各器官中以花的N、P含量最高。(2)沙化程度仅对C、N含量及C:P影响显著,而器官是影响单叶蔓荆C、N、P含量及化学计量比的主导因子;单叶蔓荆基于质量的N、P含量之间的关系在不同沙化程度区未发生策略位移现象,N:P化学计量比具有保守性特征,没有随沙化程度与器官的改变而发生显著变化。(3)单叶蔓荆各器官的相关性主要集中在地上部分,其中枝条与匍匐茎之间的关系最为密切,二者之间的C、N、P含量及C:N、C:P化学计量比均表现为显著性相关。

Aims The objectives were to clarify the responses of C, N and P stoichiometry of Vitex rotundifolia to desertification, and determine the C, N and P stoiehiometric relationships among the organs. Methods In this study, different organs （e.g. flowers, leaves, twigs, creeping stems, fine roots） of V. rotundifolia were sampled along a desertification gradient in a typical Poyang Lak sandy hill. Subsequently, C, N and P contents of various organs were measured. Important findings The results showed nutrient contents in different organs ranged from 386.28 to 449.47 mg·g^-1 for carbon, 11.40 to 25.37 mg·g^-1 for nitrogen and 0.89 to 1.54 mg·g^-1 for phosphorus, respectively. C, N and P contents differed significantly among the five organs. The maximum N and P content were found in flowers, whereas the minimums were observed in twigs and creping stems. Moreover, desertification intensity only sig- nificantly affected C, N and C：P. C：N and N：P ratios maintained relatively stable. Except N：P, the other nutrient elements and associated stoichiometry significantly differed among the organs. Hence, organs, rather than deserti- fication intensity mainly controlled the C, N and P content and their stoichiometry variability. Although there was a positive correlation between mass-based N content （Nmass） and P content （Pmass） across the three desertification zones, the Nmass-Pmass relationship in E rotundifolia did not shift. Irrespective desertification intensity and organs, N：P stoichiometry of V. rotundifolia was well constrained. In addition, significant correlations of C, N and P con- tents among organs were mainly found in the above-ground parts, especially between twigs and creeping stems.