地形异质性对尖峰岭热带山地雨林木本植物群落结构及多样性的影响 / Effects of Topographic Heterogeneity on Community Structure and Diversity of Woody Plants in Jianfengling Tropical Montane Rainforest
【目的】探讨热带山地雨林不同地形条件下物种组成及群落结构特征差异, 评估物种与地形关联性, 为进一步探索热带山地雨林的物种共存机制提供依据。【方法】以海南尖峰岭热带山地雨林60 hm2大样地及其290种木本植物(胸径≥ 1 cm)为研究对象, 通过对大样地每块20 m×20 m样地的平均海拔、坡度和凹凸度3个地形指标进行C-均值模糊聚类, 将60 hm2大样地分为不同地形类型, 分析不同地形条件下群落物种组成、物种丰富度和植株密度的差异; 采用Torus转换检验, 对大样地中胸径≥ 1 cm的独立植株且种群个体数量大于60的230种常见木本植物进行物种与地形关联性分析。【结果】尖峰岭60 hm2大样地可分为低海拔沟谷、陡坡、高海拔沟谷和山脊4类地形, 其面积分别为12.6, 16.68, 15.08和15.64 hm2, 对应的物种丰富度分别为274, 269, 264和267种; 种-面积曲线表明, 随着取样面积增加, 同等面积条件下, 低海拔沟谷的物种丰富度始终最大, 其他3类地形物种丰富度基本处于陡坡估计值的±1.96×SE置信区间内, 三者种-面积曲线相差不大; 种-个体数累积曲线表明, 随着个体数增加, 低海拔沟谷物种丰富度的累积速率最大, 陡坡和高海拔沟谷物种丰富度基本处于陡坡估计值的±1.96×SE置信区间内, 二者种-个体数累积曲线相差不大, 山脊物种丰富度随个体数增加的累积速率最小; 高海拔沟谷植株平均胸径最大, 陡坡次之, 山脊植株平均胸径与大样地植株平均胸径相同, 低海拔沟谷植株平均胸径最小; 在各个径级内, 山脊植株密度均最大, 陡坡次之, 植株平均胸径≤ 10 cm时, 高海拔沟谷植株密度小于低海拔沟谷, 而植株平均胸径≥ 10 cm时, 低海拔沟谷植株密度小于高海拔沟谷; 对4类地形内各径级植株数占总植株数的比例进行分析, 平均胸径≥ 30 cm时, 比例表现为高海拔沟谷>陡坡>山脊>低海拔沟谷, 平均胸径≥ 50 cm时, 比例表现为低海拔沟谷>高海拔沟谷>陡坡>山脊; 低海拔沟谷中重要值最大的前3个物种为白颜树、柏拉木和大叶蒲葵, 而其他3类地形条件重要值最大的前3个物种均为大叶蒲葵、白颜树和厚壳桂; 230种常见植物中, 有203个物种(占88.3%)与至少1类地形显著相关, 高于世界上其他多个大样地; 4类地形显著负相关的物种平均数占被检测物种总数比例表征的地形异质性贡献率为23.7%。【结论】尖峰岭60 hm2大样地中不同地形条件下木本植物群落结构及多样性具有较大差异, 4类地形显著相关的物种数明显不同。地形是影响该大样地中木本植物分布的重要因素, 与其他影响因素如光照、水分、土壤等多种环境因子共同发挥作用。尖峰岭热带山地雨林森林群落具有生境特化的特性, 地形异质性对其物种多样性的维持具有重要贡献。本研究结果同样具有应用价值, 如在恢复热带山地雨林植被、改造或营建混交林时, 可以根据物种与地形的关联性, 在不同的地形条件下选择不同的物种组合。
【Objective】To further explore the species coexistence mechanisms in tropical mountain rainforest, we compared differences in species composition and population characteristics in different topographic conditions, and assessed topographic associations with species diversity.【Method】The 60 hm2 tropical montane rainforest in Jianfengling of Hainan Province containing trees (DBH ≥ 1 cm) of 290 woody species as a large plot was classified into different topographic types according to their elevations, convexities and slopes of each of the 20 m×20 m sample plots by fuzzy C-mean clustering.community composition, species abundance, and individual density among different topographic conditions were compared.Using Torus-translation tests, we examined the association between micro-topography and species for 230 woody species each with more than 60 plants with a DBH ≥ 1 cm in the plot.【Results】All sample plots of Jianfengling plot could be unambiguously assigned to one of the four topography categories, lower valley (12.6 hm2, 274 species), steep slope (16.68 hm2, 269 species), upper valley (15.08 hm2, 264 species) and ridge (15.64 hm2, 267 species).By comparing species-area relationships among these four topographies, the number of species in the lower valley was the largest.But there was little difference among other three topographies, because the numbers of species of them fell within the expected values of the steep slope ±1.96×SE.By comparing the cumulative species-individual relationships among these four topographies, the cumulative rate of the lower valley was the largest and it was the least of the ridge.But there was little difference between the steep slope and the lower valley, because the numbers of species of them fell within the significance interval of the expected values of steep slope ±1.96×SE.The upper valley had the largest average DBH, followed by the steep slope, whereas the lower valley had the least average DBH.And the average DBH of the ridge was equal to that of the whole plot.The ridge had the highest density, followed by the upper valley.The density of the tree community of the upper valley was lower than that of the lower valley, when the average DBH ≤ 10 cm.When the average DBH ≥ 10 cm, it was inverse.For the proportion of different DBH sizes, the upper valley > the steep slope > the ridge > the lower valley when the average DBH ≥ 30 cm, and the lower valley > the upper valley > the steep slope > the ridge when the average DBH ≥ 50 cm.Of the lower valley type, Gironniera subaequalis, Blastus cochinchinensis, and Livistona saribus were the most dominant species, while of the other three topographies Livistona saribus, Gironniera subaequalis, and Crypcarya chinensis were the most dominant species. 203 (88.3% of all) of 230 common species showed significant associations with the topographies, which is relatively higher than other large plots in the world.We used the mean of species negatively associated with one of the four topographies divided by the examined 230 species to assess the effects of topography.The extent that species-topography associations contributed to species coexistence was 23.7%.【Conclusion】We found that community structure, species diversity and species-topography associations were different among 4 topographies in the 60 hm2 plot in Jianfengling.Topography was one of the important environmental factors that determined species distribution in the plot, although light, moisture and soil condition may also have played roles.This study indicated that the species in Jianfengling plot had strong differentiation of micro-topographic niche.Topographic heterogeneity had important contribution to maintaining species diversity in this tropical montane rainforest.This study also provided guidance to choose different species combinations in different topographies when restoring tropical mountain rainforest, rebuilding or constructing mixed forests, according to the species-topography associations.
Abstract in Chinese and English; article in Chinse only.