华北山地典型天然次生林群落的树种空间分布格局及其关联性

Spatial distribution patterns and associations of tree species in typical natural secondary mountain forest communities of Northern China

关帝山华北落叶松、云杉、杨桦天然次生林植被类型是华北高海拔地带代表性的森林类型。以该地区上述3种典型的天然次生林群落为例,运用点格局分析中的单变量O-ring统计方法,分析各群落主要树种的种群空间分布格局;用双变量O-ring统计方法,分析各群落中树种间的空间关联性;并对同一树种在不同森林群落类型中种群空间分布格局和种间关联性的变化进行比较,以探讨华北山地次生林群落空间格局形成和种群维持与动态机制。研究结果表明,(1)各种群在相对小的尺度上聚集分布特征明显,随尺度增加树木种群的聚集性减弱并逐渐表现出随机分布的格局特征;(2)同一树种在不同森林群落类型中空间分布格局差异很大。红桦、白桦和山杨在阔叶林中呈明显的小尺度聚集分布格局,而在针叶林群落呈随机分布。在阔叶次生林中混生的小龄级华北落叶松呈现聚集性空间分布格局。在华北落叶松为优势树种的针叶林中,大龄级的华北落叶松表现出小尺度上均匀分布和较大尺度上随机分布的格局特征;(3)各群落中树种间的空间关联性主要表现在小尺度范围,随尺度加大空间关联性逐渐不明显;(4)在阔叶树占优势的次生林,小龄级华北落叶松与桦木的分布有较明显的空间正关联性,而在华北落叶松为优势树种的针叶林,桦与华北落叶松并未表现明显的空间关联性。种群分布格局和种群间的空间关联性随群落结构、空间尺度和龄级结构不同而有较大变化。

Analyzing spatial patterns of species can provide many important clues about the underlying processes that have generated these patterns.Natural secondary prince rupprecht′s larch forest,spruce forest and poplar-birch forest in Guandi Mountain are representative forest types of high altitude area in Northern China.In this study,the three typical natural secondary mountain forest plots narrated above were established to analyze and compare spatial patterns of dominant tree species populations.In the plots,all arbor species at least 1cm diameter at breast height（DBH,1.3m above ground） were mapped and identified to species,and their geographic coordinates were recorded following a standard field protocol.The pair correlation function,univariate O-ring statistic of the point pattern analysis,was used to analyze spatial distribution of tree species in each community,while bivariate O-ring statistic was used to analyze spatial associations of different species in each community.The change of population spatial pattern and association for same species among different forest communities was compared to explore inherent formation mechanism of spatial patterns.We found that：（1） Most populations in three communities showed significantly aggregated distributions at relatively smaller scales and random distributions at larger scales,and the degree of aggregation decreased with increasing spatial scales（2） There are large differences among the spatial patterns of the same species in different forest communities.Betula albo-sinensis,B.platyphylla and Populus davidiana were significantly aggregated at smaller scales in deciduous forests,but randomly distributed in conifer-dominated forests.For Larix principis-rupprechtii,The young trees were aggregated in mixed broadleaved secondary forest,while the old ones were regularly distributed at small scales and randomly distributed at large scales in Larix principis-rupprechtii-dominated conifer forests.（3） Spatial associations among tree species in the three communities were mainly found at smaller scales and gradually disappeared with increasing scales.In broadleaved species dominated secondary forest,there were significantly positive associations among the young Larix principis-rupprechtii and Betula species.However,in Larix principis-rupprechtii-dominated conifer forest,there was no significant association among them.In summary,spatial pattern and associations of tree species in the three communities varied greatly with tree age,size and community structure.This study result aims at providing a theory basis for going deep into a cognition for the formation of spatial patterns,the maintenance mechanisms and dynamics of the populations,knowing further about biodiversity and species coexistence mechanisms of mountain secondary forest communities of Northern China.