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| 色季拉山东坡急尖长苞冷杉种群结构与动态 |
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任毅华1,2,3, 罗大庆1,2,3, 方江平，等1,2,3
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1.西藏农牧学院 高原生态研究所;2.西藏林芝高山森林生态系统国家野外科学观测研究站;3.西藏高原森林生态教育部重点实验室
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| 摘要: |
| 【目的】研究西藏色季拉山急尖长苞冷杉（Abies georgei var. smithii）种群的结构动态及演替趋势，为该种群的保护与恢复提供参考依据。【方法】在色季拉山东坡海拔3 800 m处设立100 m×100 m的典型样地，对固定样地内所有基径≥0.1 cm的乔木树种进行调查，记录树高、基径、胸径、生长状况等信息，对于基径＜0.1 cm的幼苗采用抽样调查统计其数量。采用基径和胸径2个指标将急尖长苞冷杉种群划分为13个龄级，分析该种群的龄级结构；利用种群动态量化方法计算相邻龄级种群数量动态变化指数（Vn）和种群结构对随机干扰的敏感性指数（Pmax）等；采用种群静态生命表、生存分析等方法，分析种群结构特征；采用时间序列预测模型对种群未来数量动态变化趋势进行量化预测。【结果】（1）色季拉山急尖长苞冷杉种群呈典型的“金字塔”型，1龄级幼苗储备丰富。（2）种群数量动态变化指数显示该种群为增长型种群，但对外界干扰具有较高的敏感性。（3）种群林龄结构完整，1龄级阶段存在强烈的环境筛选作用，种群存活曲线趋向于直线型（Deevey-Ⅱ型）B3亚型，种群死亡率与消失率随龄级的增大先降低后升高再降低。（4）生存分析表明，随龄级的增大，种群生存率逐渐降低，累积死亡率与生存率为互补关系，死亡密度与危险率总体呈降低趋势，但危险率曲线波动较大。（5）时间序列预测模型结果表明，急尖长苞冷杉种群在未来一段时间内呈增长趋势，与种群结构及数量动态变化指数分析结果一致。【结论】虽然各种指标均表明急尖长苞冷杉种群目前处于稳定增长期，但结合生境及气候条件认为，该种群目前处于以地形、风、雪为主导的一种多元演替顶级的稳定期，今后一段时间其种群数量虽有波动，但不会偏离目前整体状态。考虑该种群对外界干扰具有较高的敏感性，建议进一步加强生境的保护，防止生境破坏引起种群衰退。 |
| 关键词: 急尖长苞冷杉 种群结构 种群存活曲线 生存分析 时间序列 色季拉山 |
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| 基金项目:西藏自治区自然科学基金项目（XZ 2018 ZR G-17）；西藏农牧学院研究生创新计划项目（YJS2019-23）；国家自然科学基金项目（31060113）；西藏特色农牧资源研发协同创新中心（高原生态项目） |
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| Structure and dynamics of Abies georgei var.smithii population in eastern slope of the Sejila Mountains |
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REN Yihua,LUO Daqing,FANG Jiangping,et al
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| Abstract: |
| 【Objective】This study investigated population structure and succession trends of Abies georgei var.smithii in the Sejila Mountains,Tibet to provide a reference for its protection and restoration.【Method】A typical sample plot of 100 m×100 m was set up at the altitude of 3 800 m on east slope of the Sejila Mountains.All tree species with base diameter ≥0.1 cm in the fixed sample land were investigated.Tree height,base diameter,diameter at breast height (DBH) and growth status were recorded.The number of seedlings with base diameter ≤0.1 cm was measured by sampling survey.The population of A. georgei var.smithii was divided into 13 age classes by two indexes of base diameter and DBH to analyze age structure.The dynamic change index (Vn) of population number and the sensitivity index of population structure to random disturbance (Pmax) bearing external interference were calculated according to the population dynamic quantitative method.The population structure characteristics were analyzed by means of static life table and survival analysis.The trend of population dynamic change in the future was predicted by the time series prediction model.【Result】(1) The population of A. georgei var.smithii in the Sejila Mountains was in a typical pyramid type,and the reserves of 1-year-old seedlings were abundant.(2) The population dynamics index showed that the population was increasing,but it was highly sensitive to external disturbances.(3) The survival curve tended to be linear (Deevey-Ⅱ) subtype B3.With the increase of age class,mortality and disappearance rate of the population showed a trend of decrease,increase and decrease.(4) Survival analysis showed that survival rate of the population gradually decreased with the increase of age class,while cumulative mortality and survival rate were complementary.The mortality density and risk rate showed a downward trend,but risk rate curve fluctuated greatly.(5) The time series prediction model showed that the population of A. georgei var. smithii was increasing in the future,which was consistent with the results of population structure and population dynamic index.【Conclusion】Although various indexes indicated that the population was in a stable growth,this study suggested that the population was in a stable period of multiple succession top dominated by topography,wind and snow based on habitat and climatic conditions.The fluctuation of population number would not deviate from the current overall state.Considering the high sensitivity of the population to external interference,it is suggested to enhance the protection of habitat to avoid population decline. |
| Key words: Abies georgei var.smithii population structure population survival curve survival analysis time sequence the Sejila Mountains |
