庞泉沟自然保护区寒温性针叶林演替优势种格局动态分析

Dynamic analysis on spatial pattern of dominant tree species of cold-temperate coniferous forest in the succession process in the Pangquangou Nature Reserve

以华北落叶松和青杆为主的寒温性针叶林是庞泉沟自然保护区的重要林型,也是主要保护对象之一。通过空间代时间构建庞泉沟自然保护区寒温性针叶林演替的时间序列,序列1是华北落叶松单优群落稳定发展的过程,序列2是从华北落叶松单优群落演替至华北落叶松-青杆共优群落再到青杆单优群落的过程,采用点格局分析法和与Monte-Carlo拟合检验对演替过程中华北落叶松和青杆的分布格局及其相互关系进行了研究。结果表明:(1)序列1在华北落叶松单优群落稳定发展过程中,华北落叶松的分布格局由集群分布趋向于随机分布,甚至在0—2.5 m上表现为均匀分布,驱动力是种内竞争引起的自疏现象。序列2从华北落叶松单优群落演替至青杆单优群落过程中,华北落叶松的分布格局同样是由集群分布趋向于随机分布,驱动力主要来自于由于青杄侵入扩散而形成的种间竞争;青杄集群的尺度逐步增大,驱动力主要是种群拓殖和种内竞争。(2)二者种间关系,在华北落叶松单优群落阶段无明显相关,共优阶段由于竞争在0—6.5 m尺度上呈显著正相关,在青杄单优群落,青杄竞争获胜,在0—2.5 m尺度上无明显相关,二者种间关系的变化主要来自于群落剩余资源驱动下的种内种间竞争。

The dynamics and characteristics of population patterns in the vegetation succession process are rarely explored. Scale, pattern and process of ecological succession are three intertwined concepts in modern ecology. Succession research will inevitably involve scale and pattern analyses. Species spatial patterns and interspecific associations at any scale can be analyzed based on point pattern analysis with spatial mapped points of individuals＇ distribution. Therefore, it is suitable to discuss the relationships between species pattern in the vegetation succession process which have attracted much attention from ecologists. The aim of the present work is to study the spatial pattern formation and relative importance of intra and interspecific competition in dominant tree species of cold temperate coniferous forest in the vegetation succession process in the Pangquangou Nature Reserve. The selected forest communities were treated as a time series of successional stages for the traditional space-for-time succession approach by applying the point pattern analysis.Pangquangou Nature Reserve is located in the midst of Luliang Mountain rangeat 37°5＇--37°55＇ N, 111°22＇-111 °33＇ E. It was established for the conservation of the first-class nationally protected bird, Crossoptilon mantchuricum, and the cold-temperate coniferous forest. Cold temperate coniferous forest dominated by Larix principis-rupprechtii and Picea wilsonii is an important vegetation formation and has a large distribution area in Pangquangou Nature Reserve. It playssignificant role in water conservation, eco-tourism, biodiversity maintaining etc. in the Pangquangou Nature Reserve. Many research have been conducted, however few of them concerning the distribution patterns of dominant species in the succession process. In the present research, two time series of ecological succession of cold-temperate coniferous forest in the Pangquangou Nature Reserve were established through spatially-sampled data substitution. The first time series reflected the stable development process of Larix principis-ruppreehtii as the monodominant community ; the second ones reflected the process from Larix principis-rupprechtii as the monodominant community to Larix principis-rupprechtii and Picea wilsonii as the co-dominant communities and then to Picea wilsonii as the monodominant community. Point pattern analysis and Monte- Carlo simulation test were used to analyze the spatial pattern of the two dominant species and their interaction relationship. The following conclusions were drawn. 1 ） During the stable development process of Larix principis-rupprechtii reflected by the first time series, the spatial pattern of the species changed from clumped to nearly random distribution and even to uniform distribution at 0-2. 5 m scale, which was driven by the intraspecific competition caused by the self-thinning effects ; during the process from Larix principis-rupprechtii to Picea wilsonii as the monodominant community reflected by the second time series, the spatial pattern of Larix principis-rupprechtii also gradually changed from clumped to nearly random distribution, which was mainly caused by the colonization and expansion of Picea wilsonii and the resulted interspecific competition. Besides, the spatial scale of Picea wilsonii community gradually increased, with the species colonization and intraspecific competition as the major causes. 2 ） In terms of the interspecific competition between the two species, no obvious relationship was found when Larix principis-rupprechtii acted as the monodominant community, significant positive relationship was identified at 0-6. 5 m scale at the co-dominant stage, and no obvious relationship was found at 0-2. 5 m scale when Picea wilsonii became the dominant species. The change of relationship between the two species was mainly driven by the intraspecific and interspecific competition for residual resources.