雅鲁藏布江三大支流流域小花水柏枝种群结构及动态特征

小花水柏枝(Myricaria wardii)为西藏特有物种，是重要的藏药资源，主要分布于雅鲁藏布江（简称雅江）三大支流河谷流域。为探索小花水柏枝种群结构及分布特征，在雅江三大支流拉萨河、年楚河和尼洋河流域设定15个样点，每个样点5个样方，测量小花水柏枝的基径大小，用径级大小划分年龄结构，通过编制静态生命表并绘制存活曲线来描述种群结构，并使用种群动态量化和时间序列分析预测小花水柏枝种群数量变化。结果表明：雅江三大支流小花水柏枝种群径级结构均为底部狭窄中部膨大的非典型金字塔结构。动态指数显示三大支流小花水柏枝种群均为增长型但增长趋势不明显，并且对外界干扰比较敏感，抗干扰能力较差。静态生命表及相关曲线显示三大支流小花水柏枝种群存活数量和生命期望随着径级增大逐渐下降，三大流域小花水柏枝种群均发生不同程度的波动，整体呈现不稳定的状态。生存分析和时间序列分析均表明缺乏幼苗是导致未来小花水柏枝衰退的主要原因，且预测年楚河和拉萨河小花水柏枝种群将更快进入衰退期，尼洋河流域小花水柏枝种群衰退期较晚。同时，幼苗所占比例与居群所在地降水量显著正相关，因此高降水量的尼洋河流域更适合小花水柏枝的生存。然而此环境的小花水柏枝种群数量对干扰较敏感，建议在雅江三大支流流域经济发展的同时加强对小花水柏枝种群幼苗保护，保护和改善小花水柏枝种群生境，以维持其种群的天然更新和恢复。

Population structure and dynamic characteristics of Myricaria wardii in the basin of three branches of Yarlung Zangbo River

Myricaria wardii is one of species of Myricaria,which is endemic to Tibet and an important resource of Tibetan medicine. It is mainly distributed in the basin of three branches of Yarlung Zangbo River (or Yarlung River, for short), namely Niyang River, Lhasa River and Nianchu River. In order to explore the population structure and distribution characteristics of M.wardii species, 15 sample plots and 5 sample sites in each plot, were determined, and from which we collected basic diameter of M.wardii. Population dynamics quantization and time sequence analysis were used to predict potential population changes of M.wardii. Characteristics of the population structure were described by establishing a static life table and drawing a population survival curve. The results showed that the population diameter class structure of M.wardii species in the basin of three branches of Yarlung River was atypical pyramid structure with narrow bottom and enlarged middle. The dynamic index showed that the population of M.wardii. in the three tributaries were all growing, but the growth was not obvious, and they were sensitive to external disturbances and had poor anti-interference ability. The static life table and the correlation curve showed that the survival number and life expectancy of the populations of M.wardii in the three tributaries gradually decreased with the increase of diameter class. The populations of M.wardii in the three tributaries all fluctuated to varying degrees, showing an unstable state as a whole. Both survival analysis and time series analysis showed that the lack of seedlings was the main reason for the decline of M.wardii in the future, and it was predicted that the populations of M.wardii in the Nianchu River and Lhasa River would enter the decline period sooner, while the decline period of the populations of M.wardii in the Niyang River were relatively later. At the same time, the proportion of seedlings was significantly positively correlated with the precipitation where the population was in, so that the Niyang River Basin with high precipitation was more suitable for the survival of M.wardii. However, the population of Myricaria wardii is more sensitive to disturbance in this environment. It is recommended to strengthen the protection of the seedlings of M.wardii population while developing economy of the three tributaries of the Yarlung River, then protect and improve the population environment of M.wardii, so as to maintain its natural renewal and recovery.