雌雄异株东北红豆杉针叶和枝条生态化学计量特征

Characteristics of ecological stoichiometry in needles and twigs of dioecious Taxus cuspidata

【目的】雌雄异株树种在维持森林生态系统的生物多样性和稳定性方面发挥着重要作用。量化雌雄东北红豆杉Taxus cuspidata 5个年龄针叶和枝条生态化学计量特征,探究东北红豆杉两性植株生长的限制性营养元素,为该种群的生态保护与恢复途径提供理论支撑。【方法】以天然成年的东北红豆杉雌雄植株为研究对象,分别采集0~4年生的针叶和枝条,分析其碳(C)、氮(N)、磷(P)含量及碳氮比(C∶N)、碳磷比(C∶P)与氮磷比(N∶P),采用标准主轴回归斜率检验同一器官两两元素之间、针叶与枝条同一元素的异速或等速增长关系。【结果】东北红豆杉雌雄植株5个年龄针叶和枝条C、N、P含量及C∶N、C∶P与N∶P的范围分别为470.25~506.75、459.73~506.13,16.17~22.47、6.85~16.02,1.33~2.51、1.00~2.61 mg·g^(-1),22.12~30.13、31.16~68.20,198.64~357.63、178.74~475.55和8.98~12.24、5.98~7.14。除了当年生针叶C、4年生针叶C、P含量和N∶P、2年生枝条P含量和C∶P及3年生枝条C含量外,东北红豆杉同一年龄针叶或枝条C、N、P含量及其化学计量比在雌雄植株间差异不显著(P>0.05)。针叶或枝条N与P之间均呈显著的正相关关系(P<0.05)。针叶P含量的变化速率高于其N含量的变化速率,两者为异速关系;而枝条N、P含量之间为等速关系。针叶N(或P)含量随枝条相应元素含量的异速增长斜率均显著小于1(P<0.05),而且针叶与枝条N含量的斜率仅为P含量的一半左右(P<0.05)。【结论】雌雄东北红豆杉针叶或枝条化学计量模式没有出现明显的性别二态性,针叶N与P含量、针叶与枝条N(或P)含量变化速率存在不协调关系,针叶或枝条均受到一定程度的N限制。

【Objective】Dioecious tree species play an important role in maintaining the biodiversity and stability of forest ecosystems.In order to provide theoretical support for the conservation and restoration of dioecious Taxus cuspidata,we quantified the ecological stoichiometry characteristics and explored the limited nutrients in five successive age classes of needles and twigs for female and male T.cuspidata.【Method】The contents of carbon(C),nitrogen(N),and phosphorus(P)and their stoichiometric ratios in the 0-4-yearold needles and twigs in female and male T.cuspidata mature trees in the field were investigated.The scaling exponents of standardized major axis regressions were used to test the allometric or isometric relationships between pairwise elements in the same organ and the same element in needles and twigs.【Result】The contents of C,N and P,and the ratios of C∶N,C∶P and N∶P in the five age classes of needles and twigs for female and male T.cuspidata were in the range of 470.25-506.75,459.73-506.13;16.17-22.47,6.85-16.02;1.33-2.51,1.00-2.61 mg·g^(-1);22.12-30.13,31.16-68.20;198.64-357.63,178.74-475.55;8.98-12.24,5.98-7.14,respectively.Except for C in the current year needles,C,P,and N∶P in the 4-year-old needles,P and C∶P in the 2-year-old twigs,and C in the 3-year-old twigs,there were no significant differences in the contents and stoichiometric ratios of C,N,and P of needles or twigs between the male and female plants at the same age(P>0.05).Furthermore,N and P in needles(or twigs)showed a linear positive correlation(P<0.05),and the change rate of P in needles was higher than that of N in needles,which showed an allometric relationship.In addition,the scaling exponents between needle N(or P)and twig N(or P)were significantly less than 1(P<0.05),and the value for N was about half of that of P(P<0.05).【Conclusion】These results suggested that there were no obvious sexual dimorphisms in stoichiometric characteristics between mature female and male T.cuspidata.The relationship between N and P in needles or N(P)between needles and twigs was not synergistic.The N contents of needles and twigs in both genders were limited to a certain extent.