常绿阔叶林谱系多样性对幼苗存活率的影响

DETECTING EFFECT OF PHYLOGENETIC DIVERSITY ON SEEDLING MORTALITY IN AN EVERGREEN BROAD-LEAVED FOREST IN CHINA

密度制约机制对于维护生物多样性有非常重要的作用。随着对密度制约机制的深入研究,人们逐渐认识到:不仅在种内存在密度制约效应,亲缘关系相近的物种之间也可能表现出密度制约效应。Webb在2000年提出的NRI(净种间亲缘关系指数)、NTI(净最近种间亲缘关系指数)考虑了比较全面的谱系信息,获得了广泛的应用。该文采用NRI、NTI来代表种间关系,并用Logistic回归模型来分析了谱系因子对浙江省开化县古田山自然保护区24hm2永久监测样地中501个幼苗样方死亡率的影响。通过对6次幼苗调查数据的分析表明:不仅相同物种密度对于幼苗的死亡率有显著影响,当密度达到一定水平时,谱系因子同样也对幼苗的死亡率有显著影响——苗区中个体间的亲缘关系越近,幼苗个体的死亡率越高。

Aims Negative density dependence plays an important role in maintaining forest biodiver-sity. Ecologists found this mechanism operates not only between conspecifics but also between closely related heterospecifics. Our objective was to determine whether phylogenetic diversity affects seedling mortality at different scales. Methods We used net relatedness index （NRI） and nearest taxon index （NTI） to represent phylogenetic diversity and employed logistic regression modeling. We analyzed the relationship between seed-ling mortality and phylogenetic diversity using the seedling dynamic data from six seedling censuses of 507 seedling plots at Gutianshan Nature Reserve during May 2006 and November 2007. Important findings We found that higher density of conspecifics resulted in higher seedling mortality,and phylogenetic diversity was responsible for seedling mortality when seedling density was high （3.46 individuals.m–2）.