阔叶红松林大径级个体对树木空间分布的影响

The influence of large trees on spatial distribution in broadleaved Korean pine forests

对森林空间结构的研究一直是生态学重要研究内容之一,林分中大径级个体直接影响周围林分的空间格局,当大径级个体成为倒木或枯立木时会造成较大林隙,这也将导致周围空间格局发生变化。利用小兴安岭凉水自然保护区内10.4 hm2样地的调查数据,统计了样地内乔木树种组成,分析计算样地内树木个体间的分布规律,探究大径级个体对周围邻木空间分布的影响。研究结果表明:样地中共有乔木24种,共计7412株(去除分株),隶属于11科18属,林分中大径级个体周围存在由小径级树木聚集生长形成的环形结构,该环形结构随着邻木径级的变化而变化,2级邻木(5.0 cm≤DBH<10.0 cm)主要在距离大径级个体3—7m范围内形成环形结构,3级邻木(10.0 cm≤DBH<30.0 cm)主要在距离大径级个体3—6 m范围内形成环形结构,而1级邻木(1.0 cm≤DBH<5.0 cm)与4级邻木(30.0 cm≤DBH<50.0 cm)并未形成环形结构,经分析环形结构的产生与林分内个体间的竞争存在密切关系,并且该结构与林隙斑块动态理论间存在内在联系,该结构是森林动态变化的一种表现形式,会伴随林木的生长产生或消失。研究表明大径级个体胸径的变化对邻木的环形结构分布范围也有一定影响,当大径级个体胸径增加时邻木的聚集范围有收缩的趋势。

Forest spatial structure has always been an important topic of ecology research. This research has a key significance on the management and maintenance of forests. However,the research has yet not attained robust knowledge on these processes. Moreover,there is a lack of reliable supporting data,and research on changes in forest spatial patterns is not sufficient. Large trees in forest stands affect spatial pattern directly; large trees cause large gaps when they fall or become dead standing trees,thus resulting in changes in spatial patterns. In this study,we used 10.4 hm 2 of forest sample data at Liangshui Nature Reserve in the Lesser Khingan Mountains (Northeast China). We obtained location coordinates, DBH of each individual tree in the sample,and analyzed the forest spatial patterns to elucidate the distribution among individuals within the forest stand. We statistically analyzed the composition of tree species and explored the effect of large trees on the spatial distribution of adjacent trees. The results showed that a total of 24 tree species in 18 genera and 11 families were recorded among the 7412 individuals. Additionally,a circular structure of small trees surrounded a large tree, and the circular structure changed with the diameter of the small trees. The diameter class 2 of adjacent trees (5.0≤DBH< 10.0 cm) form circular structures in the radius of 3—7 m from large diameter individuals and diameter class 3 of adjacent trees (10.0 cm≤DBH<30.0 cm) form circular structures in the radius of 3—6 m from large diameter class individuals. However,the circular structure was not found in diameter class 1 of adjacent trees (1.0 cm≤DBH<5.0 cm) and diameter class 4 of adjacent trees (30.0 cm≤DBH<50.0 cm). The formation of a circular structure was closely related to the competition among individuals in the forest,and there was an internal relationship between structure and dynamic theory. Structure is also a manifestation of dynamic change in forests,which will appear or disappear with forest growth. In addition,the change in large trees' diameter class affects the distribution of the circular structure. The larger the diameter of the large tree,the narrower the scope of gather,the more obvious the circular structure. This shows that the traditional explanations that the degree of aggregation of adjacent trees decreases near large trees,and the larger the diameter of larger trees,the lower the degree of aggregation,are not always correct. However,this study used single-time data,further studies are required to determine changes in circular structures over time.