甘南高山林线岷江冷杉—杜鹃种群结构与动态

Population Structure and Dynamics of Original Abies faxoniana Rehd—Rhododendron simsii Planch in High-mountain Timberline of Southern Gansu Province

高山林线是一种典型的生态交错带,是对气候反映最敏感的地区之一。甘肃南部高山林线区域主要以原始岷江冷杉种群和杜鹃种群为优势种,通过对岷江冷杉和杜鹃种群建立静态生命表,绘制存活曲线描述其结构特征,利用种群数量动态预测时间序列分析定量研究未来的发展趋势。结果显示:(1)岷江冷杉种群幼苗比较丰富,能很好的维持种群个体的自疏死亡,存活曲线呈Deevey-Ⅲ型;杜鹃种群幼苗缺乏,存活曲线趋向于Deevey-Ⅰ型;死亡曲线和危险率曲线都随着龄级的增加而增加,杜鹃种群的死亡率在各个龄级一直大于岷江冷杉种群,危险率在Ⅱ龄级以后杜鹃种群也始终大于岷江冷杉种群。(2)岷江冷杉种群结构动态变化指数Vpi大于修正后的种群结构动态变化指数V′pi且大于0,而杜鹃种群结构动态变化指数Vpi小于修正后的种群结构动态变化指数V′pi且小于0,则岷江冷杉种群属于增长型,杜鹃种群属于衰退型,岷江冷杉、杜鹃随机干扰极大值分别为0.027、0.011,说明二者对外界干扰均比较敏感。(3)杜鹃种群时间序列预测为前期幼苗比较缺乏,中期稳定,后期衰退的动态特征,而岷江冷杉种群表现出各龄级时间变化较小,幼苗个体数较多,种群为稳定增长型,岷江冷杉更能适应甘肃南部高山林线区域当前环境。

Alpine forest line is a typical ecotone and one of the most sensitive areas to reflect the climate. The dominant species of the alpine forest line area are firs and Rhododendrons in southern Gansu Province. In order to predict the future development trend, the static life table of the fir and Rhododendron populations were established to analyze the structural characteristics and the population dynamics prediction time series. The results showed that:(1)The seedlings of Mingjiang fir were relatively abundant and could maintain the self-thinning death of individuals, the survival curve was Deevey-Ⅲ type;the amount of seedlings of Rhododendron were relatively small, and the survival curve tended to Deevey-Ⅰ type;the death curve and the risk curve increased with the age class, and the death curve of Rhododendron population was always greater than that of Mingjiang fir population. The risk rate of Rhododendron population was always larger than Minjiang fir population after the second age class.(2)The dynamic index V pi of population structure of Minjiang fir was larger than the revised dynamic index V ′ pi and greater than 0, while the dynamic index V pi of Rhododendron population structure was smaller than the revised dynamic index V pi and less than 0. The Minjiang fir population belonged to the growth type, the Rhododendron population belonged to the recession type. The maximum value of random interference of Minjiang fir and Rhododendron population were 0.027 and 0.011, respectively, indicating both of them were sensitive to external interference.(3)The time series of rhododendron population was predicted dynamic characteristics of seedling shortage, stability in the middle stage and decline in the late stage, meanwhile, Minjiang fir population was small change in time at different age levels, a large number of seedlings and a stable growth type. Minjiang fir population can adapt to the current environment in the alpine forest line region of southern Gansu Province better.