荒漠河岸多枝柽柳灌丛碳氮磷化学计量特征及其影响因素

为了解群落水平下荒漠河岸多枝柽柳（Tamarix ramosissima Ledeb.）灌丛的碳氮磷化学计量特征及其影响因素，在黑河下游荒漠河岸3 800 m范围内，沿垂直河道方向上设置9个采样点，采用相关性分析、冗余分析（RDA）和偏冗余分析（pRDA）方法，对多枝柽柳群落的碳氮磷化学计量格局及其与环境因子的关系进行研究.结果表明:黑河下游荒漠河岸多枝柽柳群落TC、TN、TP含量平均值分别为380.27、30.42和1.54 mg/g，C:N、C:P和N:P平均值分别为12.98、257.09和20.04.与全球和区域尺度物种水平研究相比，黑河下游荒漠河岸多枝柽柳灌丛群落具有较低的TC含量、较高的TN含量和N:P以及相对稳定的TP含量.多枝柽柳灌丛群落碳氮磷化学计量特征变异系数相对较小，内稳性较强，相对较高的N:P（14.55~27.20）表明群落水平下多枝柽柳灌丛更倾向于受磷元素的限制.在沿河梯度上，多枝柽柳群落TC含量和TN含量均随沿河距离的增加呈显著下降的变化趋势，而C:N随沿河距离的增加呈波动上升的变化趋势；TP含量呈先降后升的变化趋势，而C:P和N:P大致呈先上升后下降的变化趋势.多枝柽柳灌丛群落的碳氮磷化学计量特征与土壤理化属性存在一定相关性，土壤含水量、土壤容重和土壤pH是影响多枝柽柳群落碳氮磷化学计量特征变化的关键因子，三者共同解释了总变异的57.7%，其中土壤含水量解释了总变异的32.8%.研究显示，土壤水盐与多枝柽柳灌丛的碳氮磷化学计量特征关系密切，土壤含水量在解释多枝柽柳灌丛碳氮磷化学计量特征变化方面比土壤pH更为重要. 

Carbon, Nitrogen and Phosphorus Stoichiometric Characteristics of Tamarix ramosissima Ledeb. Shrubland and Their Influencing Factors in a Desert Riparian Area of China

In order to explore the community level stoichiometric characteristics of Tamarix ramosissima Ledeb. shrubland and their influencing factors in an arid desert riparian area, 9 sites were vertically sampled within 3800 m from the downstream of Heihe River. The stoichiometric patterns of carbon, nitrogen and phosphorus in a T. ramosissima community and their relationship with environmental factors were studied by correlation analysis, redundancy analysis (RDA) and partial redundancy analysis (pRDA). The results show the mean TC, TN and TP contents for the T. ramosissima community were 380.27, 30.42 and 1.54 mg/g, respectively. The mean C: N, C: P and N: P ratios for the T. ramosissima community were 12.98, 257.09 and 20.04, respectively. Compared to the results of species level at the global and regional scales, the T. ramosissima community was characterized by lower TC, higher TN and N: P, and relatively stable TP contents. The variation coefficients of the community level stoichiometric characteristics were much lower and their stoichiometric homeostasis was relatively strong. The relatively high N: P levels (14.55-27.20) indicate that the T. ramosissima community might be more heavily limited by P at the community level. Along the river gradient, the TC and TN contents in the T. ramosissima community decreased significantly with distance from the river, but the C: N ratio increased and fluctuated with distance. The TP content of the community decreased and then increased, while the C: P and N: P ratios increased and then decreased with distance. The stoichiometric characteristics and soil physicochemical properties were correlated, and RDA analysis demonstrates that the soil water content, soil bulk density and soil pH had significant impacts on the stoichiometric characteristics of the T. ramosissima community and jointly accounted for 57.7% of the total variation, of which soil moisture accounted for 32.8%. Our observations indicate that soil water and saline-alkali properties were closely related to the stoichiometric characteristics of the T. ramosissima shrubland and that soil water content had a stronger impact on the community stoichiometry variations than soil pH.