珍稀特有植物华顶杜鹃的种群结构和种间联结

华顶杜鹃（Rhododendron huadingense）因分布地域的局限和资源量的稀少，被列为浙江省珍稀濒危植物。基于珍稀特有植物华顶杜鹃主要分布区的样地调查数据，通过分析群落相似性、种群结构，并基于2×2联列表，应用共同出现百分率PC、联结系数AC、Pearson积矩相关系数r_p和Spearman秩相关系数r_s等方法对华顶杜鹃乔木层22个主要物种、灌木层24个主要物种的种间联结的显著性和关联强度进行了定量测定，以揭示华顶杜鹃群落不同结构层次中主要物种的种间关系及其种群濒危的原因。结果显示：（1）华顶杜鹃生长在光照较强的阳坡，不同产地所处群落物种组成差异较大。（2）种群结构显示，各群落均处于不同程度的衰退阶段，幼苗和幼树储备不足，种群呈衰退趋势；各样地的龄级结构不完整，普遍出现断代现象。（3）方差比率VR和统计量W表明，华顶杜鹃群落中物种整体关联性不显著；PC值显示乔木层和灌木层共507个种对，有183个相互独立，其余大部分PC值小于0.6，联结性较弱；AC值显示，乔木层和灌木层中除25个种对具有显著的联结性外，其余AC值的绝对值小于0.6；r_p值和r_s值正负关联比在0.36~0.85，显著检验率在0.06~0.08。表明华顶杜鹃所在群落种间关系较为松散，整体关联性弱；大部分物种生态习性差异较大，在共存时无法达到资源的最佳分配和利用状态，群落尚处不稳定阶段。为抑制其种群的衰退趋势，应加强对华顶杜鹃个体和群落生境的保护，需要适当的人为干预。

Population structure and interspecific association of Rhododendron huadingense, a rare and endemic species in China

Rhododendron huadingense, a rare and endemic species in China, is discontinuously distributed in Zhejiang province, and it had been listed as the rare and endangered species in Zhejiang province due to its limited distribution region and small populations. We analyzed the community similarity and population structure of R. huadingense based on the data of ten plots’ survey in Zhejiang province. Based on 2×2 contingency table, percentage co-occurrence (PC), association coefficient (AC), Pearson correlation coefficient (r_p) and Spearman correlation coefficient (r_s) were used to analyze the interspecific associations among 22 dominant arbor species and 24 shrub species in the communities of R. huadingense, as well as to reveal the relationship between dominant species in different layers and the causes of endanger. The results are as follows: (1) Rhododendron huadingense is distributed in sunny slopes with high heterogeneity of communities and low Sorensen’s similarity coefficient. (2) Population structure shows that less of saplings leads to decline, age level structure is incomplete and gaps are common. (3) Variance ratio (VR) and statistic number (W) of overall associations show insignificant association of species in communities. PC values show that 183 species pairs, among 507 species pairs, are mutually independent, and the rest has the PC value＜0.6, which suggests that most of the species pairs has a weak association. AC values indicate that 25 species pairs have significant association,the AC value of the rest is within the range from －0.6 to 0.6. Positive and negative association ratio of r_p and r_s are ranged from 0.36 to 0.85, significant test rate is ranged from 0.06 to 0.08, which indicates weak associations between the species in communities. Meanwhile, most of the species have different ecological habits, the optimal allocation of resources is not achieved when co-exist. The community is still in an unstable stage. In order to restrain the decline trend of R. huadingense, protection of the individual and community habitat must be strengthened, and appropriate human intervention is also required.