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1、不同植物类群物种丰富度垂直格局分形特征的比较任海保1 张林艳2 马克平1*(1 中国科学院植物研究所植被数量生态学重点实验室, 北京 100093) (2 南京大学国际地球系统科学研究所, 南京 210093)摘 要 格局和过程一直是生态学的核心问题, 该文应用/ 非布朗运动随机分形0模型, 在北京东灵山远离人为干扰地区的阴坡设置了两条宽 2 m的样带, 描述和比较了暖温带落叶阔叶林区乔木、 灌木、 草本以及总的植物物种丰富度在不同尺度上沿海拔梯度变异特征, 以及相关的生态过程。研究结果表明:1) 直接梯度法刻画了植物物种丰富度在海拔梯度上的总体变化趋势, 并不能从中获得更多的信息。/ 非布朗
2、运动随机分形0模型揭示了不同尺度上物种丰富度的空间变化并能和生态过程相联系, 研究表明该模型适合对乔木、 灌木和草本植物物种丰富度的垂直梯度格局特征进行描述, 但对总的植物物种丰富度有一定的局限性。2)乔木物种丰富度在海拔梯度上的变化主要受两种生态过程的控制, 小尺度上分形维数接近于2, 主要受独立的不具有长程相关的生态过程控制, 呈近随机分布;大尺度上分形维数接近于 1, 主要受自相关范围大、 具有长程关联特性的生态过程控制, 随海拔上升呈近似单调下降的趋势。灌木和草本物种丰富度在海拔梯度上的变化主要受 3 种生态过程的控制, 小尺度和大尺度上的特征与乔木相似;但在中等尺度上, 分形维数接近
3、于 1. 5, 它们以近似布朗运动的形式变化。虽然乔木和灌木物种丰富度在海拔梯度上变化的尺度范围相似, 但决定它们的主要生态过程完全不同, 或相同的生态过程以截然不同的方式作用于两种不同的植物类群。总的植物物种丰富度在整个尺度范围内呈现标度不变性, 这可能是由于决定其变化的生态过程作用尺度紧密相关, 也可能因为该文研究范围的局限性。关键词 生物多样性 丰富度 分形维数 尺度 垂直格局 生态过程COMPARISON OF FRACTAL CHARACTERISTICS OF SPECIES RICHNESS PATTERNS BETWEEN DIFFERENT PLANT TAXONOMIC G
4、ROUPS ALONG AN ALTITUDINAL GRADIENTREN Hai_Bao1 Z HANG Lin_ Yan2and M A Ke_Ping1* (1 Labo ratory o f Quantitative V egetation Ecology, Institute o f Botany, Chinese A cademy o f Sciences, Beijing 100093, China) (2 International Institute o f Earth System Science, Nanjing U niversity, Nanjing 210093,
5、 China)Abstract Using non_brown fractal model, this study was tailored to quantify and compare the variations of species richness of trees, shrubs, herbs and total plants along altitudinal gradients and characterize the domi2 nating ecological processes that determined the variations. Two transects
6、were sampled far away from any anthropogenic disturbances along the shady slopes of the Dongling Mountains, Beijing, China. Both transectswere continuous and 2 mwide, and every individual tree and shrub was recorded in each transect. Discrete quadrats of 1 m1 mwere located along transect A and B for
7、 estimation of herb species richness along the altitudinal gradients. The bevel interval between the quadrats was 10 m and 25 m, respectively. In the present study, transect A and B were combined into one transect AB, and 40mwas selected as optimal quadrat length alongthe altitudinal gradients for m
8、easuring plant species richness patterns. Species richness in each quadrat was calculated by a program written in Matlab 6. 0. Firstly, direct gradient analysis was used to describe the overall trends in species richness of trees, shrubs, herbs and total plantswith changes in altitude, and the non_b
9、rown fractal model was used tomore ac2 curately detect their variations at various scales along the gradient. The model assumed that each class of eco2 logical processes affecting the distribution of a variable could be represented by an independent spatial random function. Generally, ecological phe
10、nomena were determined not by a single ecological process but by multiple ones. These processes acted on ecological patterns at their own spatial scales. In the non_brown fractal model,X 收稿日期: 2004212 221 接受日期: 2005 207 207基金项目: 国家自然科学基金项目项目(39893360、 39770131 和39970136)本研究得到北京森林生态系统定位站全体工作人员, 特别是 茅
11、世森 和宋凤山两位老师的大力支持, 米湘成博士为本文编写了计算程序,谨向他们致以诚挚的谢意* 通讯作者 Author for correspondence E_mail: makpbrim. ac. cn植物生态学报 2005, 29( 6)901 909 XActa Phytoecologica Sinicathe spatial random functions were nested within a larger range of spatial scales. The relative contribution of spatial random functions to the s
12、patial variation of a variablewas indicated by aweighting parameter that had to be greater than or equal to zero. In this paper, we reached the following results and conclusions. Firstly, the direct gradient method de2 scribed the general trends of trees, shrubs, herbs and total plants along the alt
13、itudinal gradient but was unable to provide more detail about altitudinal variations of species richness. The non_brown fractal model uncovered altitudinal variations in species richness oftrees, shrubs and herbs at various scales and related themtoecolog2 ical processes. The sharp changes in the do
14、uble_logvariograms suggested that the non_bro wn fractal model was advisable for characterizing the altitudinal patterns in species richness of trees, shrubs and herbs at various scales but not appropriate for explaining the variation of total plant species richness, because there was no ob2 vious s
15、harp change in its double_log variogram. Secondly, for trees, the double_log variogramwas divided into two scale ranges (0- 245m and 245- 570m), with a fractal dimension of 1. 83 and 1. 10, respectively, im2 plying that changes in tree species richness was nearlyrandomat small scales (0- 245 m) and
16、nearly linear at large scales (245- 570 m) along the altitudinal gradients. This suggested that altitudinal variations in tree species richness were dominated by short_range processes at small scales and by long_range processes at large scales. Thirdly, for shrubs and herbs, the double_log variograms exhibited three sections (0- 101 m, 125- 298 m and 325- 570 m), and the fractal dimensionswere 1. 78 and 1. 97, 1. 56 and 1. 43, and 1. 08 and 1. 25, respectively. The results indicated
