海南岛霸王岭热带雨林的种间分离

INTERSPECIFIC SEGREGATION IN A TROPICAL RAIN FOREST AT BAWANGLING NATURE RESERVE, HAINAN ISLAND

基于地理信息系统软件绘制了海南岛霸王岭热带雨林 1个 0 .5hm2 永久样地所有DBH≥ 1cm树木的分布图 ,进而借助最近邻体分析扩展模块判定每个个体的最近邻体植株 ,并得到每个基株 最近邻体种对的距离。采用N×N最近邻体列联表的截表法 ,研究了这个多物种群落的种间分离。结果表明 ,随机毗邻种对占优势 ,正分离种对次之 ,负分离种对最少。多数灌木和一些小乔木 (平均胸径 <1 5cm)彼此呈正分离 ,少数负分离 ;灌木和乔木间的分离关系复杂 ;大乔木种类 (平均胸径≥ 65cm)间不存在负分离。种间分离存在种间差异。种间分离与分布格局明显相关 ,聚集分布的物种与其它物种正分离比例远比随机分布、均匀分布大 ;相反 ,聚集分布物种与其它物种负分离比例要比随机分布、均匀分布小。聚集 聚集分布的种对最可能出现正分离 ;聚集 均匀分布的种对以及随机 随机分布的种对则最可能出现负分离。但是 ,无论物种的分布格局或种对相对分布格局如何 ,随机毗邻的种对都占优势。与种间联结不同 ,种间分离反映的是小尺度的物种空间关系。在此基础上 。

Both interspecific association and interspecific segregation can be used to study the spatial affinity between different species. They are connected but different. Interspecific association is more related to habitat, while interspecific segregation more to small_scale effects and intra_/inter_specific interactions. Association is measured by plot sampling while segregation is measured by plotless nearest neighbor methods. Compared with interspecific association, few studies on pairwise segregation in a multi_species community have been reported. Meanwhile, clarifying the segregation relationship between different species pairs will be helpful for revealing the phenomena of the species interactions, community structure and community dynamics. With the aid of GIS software (ArcView), a distribution map of all trees with DBH≥1cm from a tropical rain forest community at Bawangling National Nature Reserve in Hainan Island was drawn. The nearest neighbors of each individual and the distances between every individual_neighbour pair were obtained by using ArcView’s nearest_neighbor extension module (Jeff Jenness’s Nearest Features v.3.5). Based on this, the spatial pattern and interspecific segregation in the multi_species community was studied with a subtable method of a N×N nearest_neighbor contingency table. Distribution pattern was measured by a revised Clark_Evans index ( CE ) and the often_used χ 2 method. Pielou’s coefficient of segregation ( S ) was adopted to measure the segregated degree between two species: while 0.7≤ S ≤1, two species are positively segregated; -1≤ S ≤-0.7, negatively segregated; otherwise they are random neighbors. In order to solve zero cell problems, each zero cell of the contingency table had 0.001 added to it. This will not change the polarity of segregation and the zero denominators will be avoided in Pielou’s equation. Pairwise segregation was shown in a constellation diagram in which solid lines stand for positive segregation, dash lines for negative segregation and different shapes for different mean DBH. The subtable method is quick, convenient and reliable. Its reliability increases with the increase of number of individuals. This is the reason we only focus on the segregation relationship between those species with more than 10 individuals. With the development of GIS software, computer simulation as well as the application of plotless sampling methods in a large area becomes possible. However, there is not any significant test for Pielou’s coefficient until today. The statistical test for such subtables is still under question for both ecologists and statisticians. In the forest community we analyzed, some species pairs are positively segregated (23.3%) and a few pairs are negatively segregated (2.4%). In contrast, the segregation relations between most of the species are random (74.3%). Our results support Pielou’s opinion that negative segregation is rare in a mature plant community. On the other hand, most understory trees (mean DBH<15 cm) are positively segregated between each other, few negatively segregated. No negative segregation occurs between large arbors (mean DBH≥65 cm). Segregation relations between understory trees and large arbors are complicated. Meanwhile, most species will not be negatively segregated with others. Some will not be positively segregated with others. Two species have both positive and negative segregated relationship, while only one species has neither positive nor negative segregation with all other species. The results also indicated that interspecific segregation is closely related to their distribution patterns. Proportion of positive segregation between clumped species and other species (31.4%) is much larger than that of random species (16.7%) or uniform species (20.0%). Proportion of negative segregation between clumped species and other species (1.3%) is less than that of random (3.3%) or uniform species (2.4%). Clumped_clumped species pairs tend to be more positively segregated (43.1%) than that of other species p