海南霸王岭热带山地雨林森林循环与树种多样性动态

The Forest Cycle and Tree Species Diversity Dynamics in a Tropical Montane Rain Forest of Hainan Island ,South China

通过对海南岛霸王岭热带山地雨林的调查 ,研究了热带山地雨林树种多样性特征随森林循环的动态变化规律。结果表明 :( 1 )热带山地雨林森林循环不同阶段斑块在森林景观中所占的面积比例分别是 :林隙阶段 ( G)占 38.5 0 % ,建立阶段 ( B)占 2 8.5 0 % ,成熟阶段 ( M)占 2 7.0 0 % ,衰退阶段 ( D)占 6 .0 0 %。 ( 2 )热带山地雨林中乔木树种的密度随森林循环的变化趋势是由 G→B→M呈现出逐渐增加的趋势 ,以成熟阶段达到最大 ,而到衰退阶段又趋于下降。灌木树种则表现出 G阶段斑块的密度最大 ,B阶段的最小 ,从 B到 M有所增加 ,到 D又稍有下降。 ( 3)热带山地雨林中不同高度级和不同径级的树木的密度在森林循环的不同阶段表现出不同的增减趋势 ,其随森林循环过程呈现出的动态变化可能与不同阶段斑块内的空间、环境及物种生物学特性有关。 ( 4 )热带山地雨林中树木的平均胸径、平均高、平均胸高断面积、平均单株材积随森林循环过程呈现出不断增加的趋势 ,其中平均胸径和平均高随森林循环的变化较为平缓 ,而平均胸高断面积和平均单株材积之变化较为陡急。 ( 5 )热带山地雨林森林循环不同阶段的物种多样性指数不同 ,其中 G和 B阶段的物种丰富度和多样性指数值较接近 ,M阶段的物种丰富度达到最大 ,D阶段则最小。

Since the initiatial work by Watt in 1947, it has been recognized that plant communities are mosaic-complexes of patches with dynamic properties. This is especially true in forest ecosystems.The natural disturbance is essential to maintain the structure, dynamics and diversity of the patch dynamics in forest ecosystem. Whitmore(1989)further developed Watt's patch dynamics into the theory of forest cycle in his studies on tropical rain forests. The theory emphasizes that forest cycle driven by disturbance exists in every forest ecosystem.The succession pathway of forest cycle could be divided into initial gap phase, building phase, mature phase, and degenerating phase. The diversity of the tree species in he forest ecosystem will change through the process of the forest cycle driven by natural disturbance. There are two ways to study the dynamic changes of species diversity in forest ecosystem. One is through permanent plots. which is believed the most effective approach to study the species diversity and its dynamics.However,it may not be a practical way to adopt in many cases because the costs to set up as well as to conduct the observations on a long term are expensive.The other is by investigating the communities at various succession stages.The theory of forest cycle has provided a new way to study the dynamics of species diversity of forest ecosystems.By establishing the relationship among the patches based on various phases along its succession pathway,and comparing the properties in species diversity between these patches,the dynamics of species diversity of the ecosystem can be understood. For both sciectific significance and practical concerns,and also giving the gap exists in the research area in the patch dynamics in forest ecosystems in China,this study is the first attempt to apply the forest cycle theory to the study of species diversity dynamics.This paper represents the works conducted in a tropical montane rain forest in Hainan Island in southern China . Population and community characteristics between patches at various succession phases in the forests were analyzed based on forest cycle theory. The purpose of this study is to explore the relationships between natural disturbance, patterns of the patch mosaic, and the dynamic changes of species diversity in the tropical montane rain forest. We carried out the field investigations in a permanent plot of size 100m×100m.The plot was divided into 400 grid quadrants with a size of 5m×5m for each grid.During the investigation,the first step was to determine the phase of forest cycle for each quadrant.Then,all the trees and shrubs avove 1.5m height were identified.Then the DBH (diameter at breast height which is 1.3m above ground) and height of the trees were measured and recorded. If more than one patch types were included in one quadrant, then the patch type of the quadrant was defined as the one with the largest area. The following standards were used to classify patch types in the forest cycle. (1) Gap phase (G):The Gap is much brighter than other places in the stand, decomposing dead logs or gap makers can be identified. In gap phase, there are seldom trees above 8m in height or 10cm in DBH. (2) Building phase (B): Gap makers or even their remains can not be found in forest at this phase. The stand is much darker than gaps. The height of the tree layer in the patch almost reaches the lower edge of the main canopy layer around the patch. However, the height difference between trees in the patch and the trees in the canopy layer of the stand is still easy to discern since it remains a open space over the stand surrounded by tall trees along the edge of the patch. Many trees in the patch are over 8m in height or 10cm in DBH. But few of them are higher than 14m or greater than 20 cm in DBH. (3) Mature phase (M): When at mature phase, most trees in the upper layer are as high as the canopy layer of the forest. Many trees are over 14m in height or 20cm in DBH, but few trees are over 50cm in DBH at this phase. (4) Degenerate ph