珍稀濒危树种峨眉含笑种群结构与动态特征

Population structure and dynamic characteristics of a rare and endangered tree species Michelia wilsonii Finet et Gagn

珍稀濒危植物峨眉含笑是中国特有树种,国家二级重点保护野生植物。为摸清其种群生存现状,了解其种群结构、动态及空间分布格局,首次对分布于中国四川省峨眉山、沐川县国有林场和平武县宽坝林场3个现存地点的峨眉含笑天然种群进行野外调查。依据空间代替时间理论和匀滑技术,建立各种群的年龄结构和静态生命表、绘制种群存活曲线、死亡率曲线和损失度曲线等阐明其种群结构特征,通过种群动态量化分析方法量化种群结构动态变化规律,并基于种群空间格局分析的多种方法分析各种群的空间分布特征。结果表明:峨眉和平武种群属于增长型,沐川种群属于衰退型;峨眉和沐川种群的存活曲线为Deevey-Ⅲ型,平武种群的存活曲线为Deevey-Ⅱ型。同一种群死亡率曲线和损失度曲线的变化趋势一致。平武种群密度最大,但小树的死亡率最高;沐川种群密度最低,幼苗严重不足,幼树、小树缺乏,中树死亡率最高,种群存在衰退的风险。峨眉种群密度介于沐川和平武之间,但幼苗、幼树的死亡率最高。因此,需针对不同分布点的种群,采取不同的保护措施。建议对峨眉种群进行人工育苗,获得该种群的实生幼苗,待幼苗长成小树后将小树移植回该种群;对沐川种群,宜采用人工优化生境及人工辅助育苗相结合的措施,促进种群更新;对平武种群应制订适宜的保护栖息地的有力措施,并呼吁当地相关部门及村民加强对该树种的保护。

Michelia wilsonii Finet et Gagn. is a rare and endangered tree species that is endemic to China. It is under second-class national protection station. To clarify the survival status of the population, better understand the population age structure, population dynamics, and analyze its spatial distribution pattern, surveys were conducted on the natural population of M. wilsonii distributed in the Emei Mountain, Muchuan State-owned Forest Farm, and Pingwu Kuanba Forest Farm in Sichuan Province for the first time. Based on the theory of space instead of time and smooth out method, we established population age structure and drew static life table. The population survival curve, mortality and vanish rate were drawn to clarify its characteristics of population age structure. The quantitative analysis of population was introduced to further analyze the population dynamics. Finally, the spatial distribution patterns of different populations were obtained on the basis of various population spatial pattern analytical methods. The results showed that the populations of Emei and Pingwu belonged to the growth population, while the population of Muchuan belonged to the decline type. The survival curves of Emei and Muchuan were Deevey-Ⅲ type, while the Pingwu population belonged to Deevey-II type. The change trend of mortality and loss curve of the same population was consistent. The density of Pingwu population was the highest but the mortality rate of saplings and small young trees was the highest. The population density of Muchuan was the lowest. Not only the seedlings were seriously insufficient, but also saplings and small young trees were lacking. In addition, the mortality of middle trees was the highest, the population was at risk of decline. The density of Emei population was between Pingwu and Muchuan population, but the mortality rate of seedlings and samplings in Emei population was also higher. Therefore, different protection measures should be taken for populations distributed in indifferent sites. It is suggested that artificial seedling cultivation should be adopted for Emei population to obtain seedlings of the population and transplant the young trees back to the population when the seedlings grow into young trees. For Muchuan population, the combination of artificial optimizing habitat and artificial assisted seedling cultivation should be adopted to promote population renewal. For Pingwu population, effective measures for habitat protection should be formulated. Local relevant departments and villagers should be called upon to protect the tree species.