Spatial variation in community structure of a subtropical evergreen broad-leaved forest: Implications for sampling design

With the full survey data for a 24-ha subtropical evergreen broad-leaved forest dynamics plot,we evaluated spatial variation in forest structure characteristics(basal area and aboveground biomass),and calculated the minimal sample size and total sampling area necessary to estimate the forest structure characteristics within 20%(±10%) of the observed values with 95% probability for particular quadrat sizes by using a computer program that is designed to simulate the sampling process by allowing different sized quadrats to be randomly located within the sampling region.We found that(1) based on the 600 20 m×20 m subplots,basal area and aboveground biomass displayed a high degree of variation,with respective coefficients of variation of 27% and 31%;(2) based on the computer simulation analysis,the variability of basal area and aboveground biomass decreased with increasing quadrat size.The number of quadrats required to achieve the specified degree of precision dropped sharply with the increase of quadrat size.However,the total sampling area increased with increasing quadrat size,suggesting that using several small quadrats across the sampling area is more efficient than using fewer larger quadrats.Results of this study are valuable for evaluating the reliability of previous research and may assist researchers in designing effective sampling strategies for future field surveys,particularly in subtropical evergreen broad-leaved forests in China.     

洛河中游河岸带不同生境类型中物种多样性研究

为研究河岸带植被不同生境类型中物种多样性变化格局,在洛河中游沿河岸带通过样地调查,采用Patrick丰富度指数(R)、McIntosh均匀度指数(E)、Simpson优势度指数(C)、Shannon-Wiener多样性指数(H)、Simpson多样性指数(D)对洛河中游河岸带不同生境类型(河滩、农田、撂荒地和林地)草本层的物种多样性进行评价,利用重要值对多样性指数中的Ni进行无偏估计.结果表明:洛河中游河岸带植物种类丰富,有33科,97属,141种,分布最多的为菊科,其次是禾本科.沿洛河河岸带不同生境类型中,物种多样性各项指标有一个明显的变化格局:丰富度指数中,河滩>林地>撂荒地>农田;多样性指数(Shannon-Wiener多样性指数和Simpson多样性指数)中,河滩>林地≈撂荒地>农田;农田均匀度最高,且优势度也最高.     

Evolution of species interactions in a biofilm community

Biofilms are spatially structured communities of microbes whose function is dependent on a complex web of symbiotic interactions. Localized interactions within these assemblages are predicted to affect the coexistence of the component species, community structure and function, but there have been few explicit empirical analyses of the evolution of interactions. Here we show, with the use of a two-species community, that selection in a spatially structured environment leads to the evolution of an exploitative interaction. Simple mutations in the genome of one species caused it to adapt to the presence of the other, forming an intimate and specialized association. The derived community was more stable and more productive than the ancestral community. Our results show that evolution in a spatially structured environment can stabilize interactions between species, provoke marked changes in their symbiotic nature and affect community function.     

城市化进程中的上海植被：多样性、空间格局和动态响应(Ⅲ)：高度城市化影响下上海中心城区杂草区系特征

通过对上海中心城区城市杂草区系的调查,分析了高强度城市化影响下杂草的多样性状况,探讨了高异质性城市生境中杂草的适应特征.在所调查的260个杂草群落样方中,共出现杂草107种,隶属32科89属,其中禾本科和菊科两个多种科含种数最多,高比例的单种属表征了城市生境具有较高的异质性;在广适性杂草对城市生境普适性的基础上,生活周期短和适应性强是一年生杂草对高强度和高频度人为干扰生境的适应策略,城市干旱的特化生境提高了冬季一年生杂草的比例.     

Large-scale processes and the Asian bias in species diversity of temperate plants

An important issue in the study of biodiversity is the extent to which global patterns of species richness reflect large-scale processes and historical contingencies. Ecological interactions in local assemblages may constrain the number of species that can coexist, but differences in diversity in similar habitats within different regions (diversity anomalies) suggest that this limit is not firm. Variation in rate of species production could influence regional and perhaps local diversity independently of the ecological capacity of an area to support coexisting species, thereby creating diversity anomalies. Temperate Zone genera of plants that are disjunct between similar environments in eastern Asia and eastern North America (EAS-ENA) have twice as many species in Asia as in North America. Because lineages of these genera in Asia and North America are mostly sister pairs, they share a common history of adaptation and ecological relationship before disjunction. Thus, the diversity anomaly in EAS-ENA genera is not an artefact of taxon or habitat sampling but reflects differences in the net diversification (speciation-extinction) of the lineages in each of the continents. Here we propose that the most probable cause of the EAS-ENA anomaly in diversity is the extreme physiographical heterogeneity of temperate eastern Asia, especially compared with eastern North America, which in conjunction with climate and sea-level change has provided abundant opportunities for evolutionary radiation through allopatric speciation.     

Species-area relationships always overestimate extinction rates from habitat loss

Extinction from habitat loss is the signature conservation problem of the twenty-first century. Despite its importance, estimating extinction rates is still highly uncertain because no proven direct methods or reliable data exist for verifying extinctions. The most widely used indirect method is to estimate extinction rates by reversing the species-area accumulation curve, extrapolating backwards to smaller areas to calculate expected species loss. Estimates of extinction rates based on this method are almost always much higher than those actually observed. This discrepancy gave rise to the concept of an 'extinction debt', referring to species 'committed to extinction' owing to habitat loss and reduced population size but not yet extinct during a non-equilibrium period. Here we show that the extinction debt as currently defined is largely a sampling artefact due to an unrecognized difference between the underlying sampling problems when constructing a species-area relationship (SAR) and when extrapolating species extinction from habitat loss. The key mathematical result is that the area required to remove the last individual of a species (extinction) is larger, almost always much larger, than the sample area needed to encounter the first individual of a species, irrespective of species distribution and spatial scale. We illustrate these results with data from a global network of large, mapped forest plots and ranges of passerine bird species in the continental USA; and we show that overestimation can be greater than 160%. Although we conclude that extinctions caused by habitat loss require greater loss of habitat than previously thought, our results must not lead to complacency about extinction due to habitat loss, which is a real and growing threat.     

对地面植被群落中稀有植物的种类数的多重抽样估计

利用矩估计和一个稳健估计方法来处理植物学家在林地的地面植被群落调查数据.在假定已经发现一些稀有植物的情况下,通过统计推断得到那些未被发现的植被的种类数.     

常绿阔叶林退化群落的物种多样性特征及影响因子分析

由于土地利用方式改变以及人为砍伐等多种原因的共同作用,导致我国各地的常绿阔叶林均发生了不同程度的退化.本项研究从物种多样性角度出发,首先对浙江天童常绿阔叶林及其退化群落的α多样性进行了对比,进而利用逐步回归的方法,从9种可能影响该地区物种多样性的因子：海拔、坡度、坡向、用地类型、土层厚度、人类干扰强度、与自然植被的距离、同主要道路的距离以及距离村庄远近中,筛选出主要因子,并分析了它们对物种多样性的影响.结果表明：（1）常绿阔叶林的α多样性要显著高于退化群落;（2）对退化群落物种丰富度影响较显著的因子主要是：土层厚度、到自然植被的距离以及用地类型.其中物种丰富度与土层厚度呈正相关,与到自然植被的距离呈负相关,而废弃的人工果园、用材林中植被的物种丰富度相对另两类用地类型要高.（3）通过把前述9个因素划分为生境、景观、人类干扰三大类型后可以发现,它们对退化群落物种丰富度的作用大小存在明显差异.三大类因素对退化群落总体的物种多样性都有显著影响;对于退化的针叶林来说,主要的影响因子是生境和人类干扰;而就退化的灌丛而言,则主要是生境因素.     

Factors influencing the natural regeneration of arrow bamboo in giant panda habitat of the north Minshan Mountains, southwestern China

To determine the effects of eco-factors on the regeneration of arrow bamboo in giant panda habitat,a field study was conducted in the Baozuo and Gonggangling Nature Reserves,Sichuan Province,China.A total of 183 quadrats(10 m×10 m) and 717 small quadrats(1 m×1 m) were investigated within the study site.Bamboo seedling density was used as an indicator of natural regeneration.Twelve factors were measured,which included topography and forest factors(elevation,slope aspect,slope degree,slope position,canopy cover,and shrub cover) and microhabitat factors(upper vegetation cover,herb cover,litter layer cover,moss cover,moss thickness,and dead bamboo density).A One-Way ANOVA was used to analyze the effects of topography and forest factors on seedling density,and a GLM(Generalized Linear Model) procedure was performed to examine the relationship between seedling density and microhabitat factors.The results indicated that elevation and canopy cover had highly significant effects on seedling density:bamboo seedling density was highest and showed the best regeneration at middle elevations(2800-3000 m) and under medium to medium-high canopy cover.Moss thickness,moss cover,and dead bamboo density were the most important microhabitat factors influencing the natural regeneration of bamboo:seedling density increased with increasing moss cover and moss thickness and decreased with increasing dead bamboo density.We propose that removal of dead bamboo and controlling grazing activities may accelerate the process of bamboo regeneration.     

Dietary overlap of snow leopard and other carnivores in the Pamirs of Northwestern China

Information about competition between carnivore species for food within high altitude regions is limited.Data collected from the Taxkorgan Nature Reserve,China revealed important interactions between snow leopard(Panthera uncia),grey wolf(Canis lupus),red fox(Vulpes vulpes)and their prey species,including domestic livestock.Sixty-four line transects were conducted in order to identify field signs of habitat occupancy and collect scats for diet analysis.High dietary overlap was observed between all three carnivore species:snow leopard and red fox(Pianka’s index=0.96),red fox and grey wolf(Pianka’s index=0.90),snow leopard and grey wolf(Pianka’s index=0.87).Snow leopard and grey wolf showed significant predation on livestock(36.8%for snow leopard and 29.4%for grey wolf in diet composition).As a pioneering exploration of the endangered snow leopard and its relationship with other species within the alpine ecosystem under livestock grazing pressure,this study contributes a greater understanding of the relationship within carnivore guild in the Pamirs whilst providing implications for conservation planning and project implementation activities in China.     

General patterns of taxonomic and biomass partitioning in extant and fossil plant communities

A central goal of evolutionary ecology is to identify the general features maintaining the diversity of species assemblages. Understanding the taxonomic and ecological characteristics of ecological communities provides a means to develop and test theories about the processes that regulate species coexistence and diversity. Here, using data from woody plant communities from different biogeographic regions, continents and geologic time periods, we show that the number of higher taxa is a general power-function of species richness that is significantly different from randomized assemblages. In general, we find that local communities are characterized by fewer higher taxa than would be expected by chance. The degree of taxonomic diversity is influenced by modes of dispersal and potential biotic interactions. Further, changes in local diversity are accompanied by regular changes in the partitioning of community biomass between taxa that are also described by a power function. Our results indicate that local and regional processes have consistently regulated community diversity and biomass partitioning for millions of years.     

黑石顶山区植被恢复过程中物种多样性的变化

采用时空替代结合样地跟踪的方法,对广东黑石顶自然保护区船底窝的皆伐火烧迹地上永久样地的植被恢复过程(0～50年)中物种多样性的动态变化进行了研究.结果发现:随植被恢复演替的进展,群落的物种多样性总体逐渐升高,优势度趋于下降,而群落的均匀度基本上保持比较高而稳定的状态.运用灰色系统理论对该样地植被演替过程中的物种多样性与主要环境因子之间进行了关联度分析,结果发现多数环境因子对研究地群落物种多样性的影响不太明显,只有群落的透光度对物种多样性的影响相对最大.     

安徽皇藏峪自然保护区青檀种群的初步研究

皇藏峪自然保护区青檀林可分为青檀纯林和混交林两种类型.在青檀纯林中乔木层和更新层只有青檀一个物种,郁闭度较低;而在其混交林中,可明显分为乔木层、灌木层和草本层,物种丰富度和群落郁闭度较高.另外,在其混交林中,各个层次的优势种明显.青檀是乔木层优势树种之一,其重要值达66%.从青檀种群内分布型指标(方差/平均数)来看,种群个体基本为集群分布.各种群的年龄结构反映保护区内青檀种群是增长型种群.     

森林作业法的历史发展与面向我国森林经营规划的三级作业法体系

从森林作业法的发展历史和概念定义开始,19世纪初期在德国执行的作业法技术体系中,第1级产品目标分为两个大类,第2级按森林形态分为5个小类,第3级按作业方式划分出14个具体的作业法.简要说明了森林作业法技术体系在全球不同区域的演化和应用发展情况;在中国多功能森林经营科学定义的基础上,论述了我国三级结构的多功能森林作业法的...     

褐翅鸦鹃春季生境选择初步研究

2012年2～4月,对广西宜州市的褐翅鸦鹃(Centropussinensis)生境选择进行了初步研究.共测量了70个20 m×20 m样方11个生态因子,对照样方88个,运用频次分析表明:褐翅鸦鹃选择利用郁闭度良好,避风性良好,水源距离10～100 m,乔木密度4～40株,灌木密度10～100株,乔木距离<1 m,灌木距离>1 m,树径<0.4 m,人为干扰距离10～100 m,食物丰富的生境.主成分分析结果表明,前4个主成分的选择特征值均大于1,其累计贡献率达70.342%,影响春季生境选择的主要因子为隐蔽性因子,次要因子是安全性和地理性因子、食物和水源因子和干扰性因子.减少人类活动对鸟类生境的破坏是促进褐翅鸦鹃种群数量和分布增加的重要途径.     

Fractals in Spatial Patterns of Vegetation Formations

Introduction The quantification of spatial patterns, a focal subject in ecological research, is used as a foundation for meas-urement and analysis of the quality of habitats and the biodiversity[1]. Historically, the dominant approach has been used to cho…     

大源湖虾类种类组成、时空分布及生物量估算

利用“蹦网”(pop-net)采样,调查了龙感湖一个湖汊—大源湖的虾类种类组成、空间分布,估算优势种类的生物量.在2002年冬季的31个采样点和2003年春季42个采样点中共采集到虾类2707尾,属于甲壳纲,十足目的2科5属.秀丽白虾(Exopalaemon modestus Heller)是大源湖虾类的优势种,占采样总数量的84.1%.根据水深分布特征和水生植被的分布格局,划分生境类型,苦草生境是各虾类分布最多的生境,冬季优势种秀丽白虾在苦草生境中的密度是8.14 ind/m2,生物量是1.59 g/m2.春季分别是2.98 ind/m2,1.04 g/m2.春季水深对虾类的分布影响较小,冬季虾类主要分布在深水区.表明水生植被是影响虾类分布的主要环境因子;在冬季,水深成为影响虾类分布的主要环境因子之一.     

四川大头茶种群优势度增长动态的初步研究

用有限空间种群增长的逻辑斯谛模型探讨了四川缙云大头茶种胸硐面积的增长规律结果是：大头茶种群在不同林分密度下的纯林中，其胸面积最大增长速度是中密度〉高密度〉低密度，达到最大增长速度的径极范围都在１８ｃｍ左右，在不同林型中，大头茶种群胸面积的最大增长速度是纯林最大，常绿阔叶林次之，针阔混交林最小，达到最大增长速度的时间以针阔混交林最长，常绿阔叶林次之，纯林最短，还讨论了大头茶种群在不同林分密度下，不同     

Multidimensional Data Querying on Tree-Structured Overlay

Multidimensional data query has been gaining much interest in database research communities in recent years, yet many of the existing studies focus mainly on ten tralized systems. A solution to querying in Peer-to-Peer（P2P） environment was proposed to achieve both low processing cost in terms of the number of peers accessed and search messages and balanced query loads among peers. The system is based on a balanced tree structured P2P network. By partitioning the query space intelligently, the amount of query forwarding is effectively controlled, and the number of peers involved and search messages are also limited. Dynamic load balancing can be achieved during space partitioning and query resolving. Extensive experiments confirm the effectiveness and scalability of our algorithms on P2P networks.     

安徽苦苣苔科植物野生种质资源分布特征及其观赏性评价

根据标本、文献资料以及实地调查,安徽省野生苦苣苔科植物现已查明为8属13种.与《安徽植物志》(第四卷)记载的9属10种比较,取消了粗筒苣苔属Briggsia、唇柱苣苔属Chirita、小花苣苔属Chiritopsis和旋蒴苣苔属Boea,改添为报春苣苔属Primulina、羚角苣苔属Dorcoceras和丹氏苣苔属Damrongia,并增添了绢毛马铃苣苔Oreocharis sericea、大花石上莲O.maximowiczii和池州报春苣苔Primulina chizhouensis三种.通过本省该科植物的分布地区、生境及地形地貌的归纳分析,表明在气候、土壤及地形等环境因素的共同影响下,该科植物呈现出狭域且间断分布的特征.最后对本省该科植物的观赏特性进行了评价,并提出了合理保护和园艺开发利用的建议.