凤阳山常绿阔叶林优势种空间格局及关联性

Spatial Distribution Patterns and Associations of Main Tree Species in Broadleaved Evergreen Forest in Fengyangshan National Reserve,China

目的:植被空间格局对了解植物群落生态学特征及过程具有重要意义,探讨凤阳山常绿阔叶林优势树种空间格局及其空间关联性,可为深入揭示其物种共存和维持机制提供背景资料。方法:基于凤阳山自然保护区0.8 hm^(2)常绿阔叶林固定样地调查数据,采用基于Ripley’s K函数的双相关g(r)函数在0~30 m尺度研究了优势树种亮叶桦(Betula luminifera)、蓝果树(Nyssa sinensis)、甜槠(Castanopsis eyrei)和木荷(Schima superba)的空间分布格局及空间关联性。结果:在完全随机模型下,亮叶桦在0~25 m尺度呈聚集分布后转为随机分布,蓝果树呈随机分布,甜槠和木荷在小尺度聚集分布(<10 m),随尺度增大转为随机分布。在异质泊松模型下,亮叶桦和蓝果树均为随机分布;甜槠和木荷在小尺度聚集,在较大尺度上呈随机乃至均匀分布。在完全随机模型下4个优势树种的空间关联性,除亮叶桦和蓝果树不相关外,其他树种两两之间均呈不同程度的的正相关,但总体相关性并不明显。在先决条件模型下,亮叶桦与甜槠在20~25 m呈弱正相关,其他树种两两之间的空间关联均为不相关。结论:主要树种的空间分布格局和种间的关联性随空间尺度的不同而变化,群落处于稳定发展阶段。

Objective:The spatial pattern of vegetation is great significance to understand the ecological characteristics and process of plant community.Exploring the dominant tree species population distribution patterns and interspecific spatial associations are helpful in elucidating the mechanisms underlying species coexistence in the middle subtropical broadleaved evergreen forest communities.Methods:Based on a stem map of a 0.8 hm2 permanent plot at Fengyangshan National Reserve,the point pattern method was used to examine the spatial distribution pattern and associations of 4 dominant tree species(Betula luminifera,Nyssa sinensis,Castanopsis eyrei,Schima superba)through univariate pairwise correlation functions and bivariate pairwise correlation functions.Results:When using a complete spatial randomness(CSR)null model,C.eyrei and S.superba had a clustered distribution across a range of scales(0-10 m),Betula luminifera showed aggregation-random distribution at 0-30 m scale,N.sinensis showed random distribution at scales of 0-30 m.Under the heterogeneous poisson process null model,B.luminifera and N.sinensis showed random distribution.C.eyrei and S.superba showed aggregated patterns at smaller scales and became randomly or uniformly distributed at larger scales.The spatial association between 4 tree species at CSR null model showed that all species were positively associated at some scales,except B.luminifera and N.sinensis showed no correlation at whole scale,at the antecedent condition null model,B.luminifera and C.eyrei was positively associated at the 20-25 m scales,other tree species showed no significant correlation at 0-30 m scales.Conclusion:Our findings provided a valuable insight into the mechanisms of biodiversity maintenance in broadleaved evergreen forest,the spatial distribution pattern and the correlation among the main tree species varied with the spatial scale,this community was in the stable development stage.