Linking Community and Ecosystem Processes: The Role of Minor Species

The link between species and ecosystem functioning is a central issue in ecology. In natural plant communities, the dominant species determine most of the productivity-related processes but what is the function of minor species? A recent hypothesis suggests that after disturbance, minor species facilitate the recruitment and abundance of dominants during re-colonization, thus indirectly determining ecosystem function. We tested this hypothesis using a long-term dataset of annual plant communities in a semiarid shrubland by comparing plant density and biomass from plots in which all vegetation had been removed; plots from which only the dominant (the annual grass Stipa capensis) had been removed, and control plots. In the absence of vegetation, the dominant failed to re-establish during the following growing season. After being removed the dominant re-established similarly to the controls. An ant exclosure experiment excluded the possibility that this was due to seed predation. In an experiment with individual dispersal units of S. capensis, we demonstrated the mechanism by which minor species can control the dominant’s abundance. Minor species indirectly govern ecosystem processes by providing structures facilitating seed soil penetration and thus recruitment of the dominant.     

Genetic Diversity within Cryptosporidium parvum and Related Cryptosporidium Species

To assess the genetic diversity in Cryptosporidium parvum, we have sequenced the small subunit (SSU) rRNA gene of seven Cryptosporidium spp., various isolates of C. parvum from eight hosts, and a Cryptosporidium isolate from a desert monitor. Phylogenetic analysis of the SSU rRNA sequences confirmed the multispecies nature of the genus Cryptosporidium, with at least four distinct species (C. parvum, C. baileyi, C. muris, and C. serpentis). Other species previously defined by biologic characteristics, including C. wrairi, C. meleagridis, and C. felis, and the desert monitor isolate, clustered together or within C. parvum. Extensive genetic diversities were present among C. parvum isolates from humans, calves, pigs, dogs, mice, ferrets, marsupials, and a monkey. In general, specific genotypes were associated with specific host species. A PCR-restriction fragment length polymorphism technique previously developed by us could differentiate most Cryptosporidium spp. and C. parvum genotypes, but sequence analysis of the PCR product was needed to differentiate C. wrairi and C. meleagridis from some of the C. parvum genotypes. These results indicate a need for revision in the taxonomy and assessment of the zoonotic potential of some animal C. parvum isolates.     

The Relationship between Local Species Richness and Species Pool: A Case Study from the High Mountains of the Greater Caucasus

The causes of linear relationships between local species richness and the size of the actual species pool in closed subalpine meadow communities and open plant communities of the alpine stony substrate (the Greater Caucasus Mountains) were analyzed using a computer simulation model. The results demonstrated that this relationship is insufficient evidence for the variation of local species richness among communities is wholly or partly determined by regional processes (the species-pool hypothesis). A relatively proportional ratio between these variables can also arise where local species richness and the size of the species pool both depend on local processes, or where local species richness is determined by local factors alone while the size of the species pool is determined by both local and regional factors.     

百花山植物群落物种多样性研究

基于百花山50个样方的调查资料，从不同类型群落的物种多样性及其与海拔的关系等方面对百花山植被进行了分析，并且用DCA排序和海拔高程排序对物种多样性在环境梯度上的分布格局进行了初步研究。结果表明：群落内不同生长型的物种丰富度指数在森林群落中大小顺序为草本层＞灌木层＞乔木层，灌丛群落主要表现为草本层﹥灌木层，只有荆条灌丛表现为灌木层＞草本层；Shannon-Wiener指数在山杨—华北落叶松群落中表现为灌木层＞草本层＞乔木层,其他森林群落为草本层＞灌木层＞乔木层，在灌丛群落中主要表现为草本层＞灌木层，只有荆条灌丛表现为灌木层＞草本层；均匀度指数在灌丛群落中表现为灌木层＞草本层，在辽东栎林和山杨—华北落叶松林中表现为灌木层＞乔木层＞草本层,而其他森林群落表现为乔木层＞灌木层＞草本层。物种多样性在DCA第一轴排序和海拔高程梯度上都表现出单峰曲线变化趋势，但拟和效果的显著程度不同：丰富度和均匀度指数在海拔高程上曲线的拟和效果优于DCA环境梯度排序效果；而多样性指数则相反。     

Lack of Congruence in Species Diversity Indices and Community Structures of Planktonic Groups Based on Local Environmental Factors

The importance of analyzing the determinants of biodiversity and community composition by using multiple trophic levels is well recognized; however, relevant data are lacking. In the present study, we investigated variations in species diversity indices and community structures of the plankton taxonomic groups–zooplankton, rotifers, ciliates, and phytoplankton–under a range of local environmental factors in pond ecosystems. For each planktonic group, we estimated the species diversity index by using linear models and analyzed the community structure by using canonical correspondence analysis. We showed that the species diversity indices and community structures varied among the planktonic groups and according to local environmental factors. The observed lack of congruence among the planktonic groups may have been caused by niche competition between groups with similar trophic guilds or by weak trophic interactions. Our findings highlight the difficulty of predicting total biodiversity within a system, based upon a single taxonomic group. Thus, to conserve the biodiversity of an ecosystem, it is crucial to consider variations in species diversity indices and community structures of different taxonomic groups, under a range of local conditions.     

莫索湾垦区啮齿动物群落结构与物种多样性分析

2004年6～8月对莫索湾垦区啮齿动物调查,按不同生境共抽取18个样地,采用铗日法进行鼠类密度调查,共置10400个铗日,捕获啮齿动物446只,分属3科9属11种。经聚类分析,该垦区鼠类群落可划分为6种群落类型：（1）以大沙鼠（Rhombomys opimus）＋子午沙鼠（Meriones meridianus）为主的荒漠型;（2）以红尾沙鼠（Meriones erythrourus）＋小五趾跳鼠（Allactaga elater）为主的半荒漠灌丛型;（3）以柽柳沙鼠（Meriones tamariscinus）＋小林姬鼠（Apodemus sylvaticus）为主的林地型;（4）以小家鼠（Mus musculus）＋小林姬鼠为主的农田型;（5）以灰仓鼠（Cricetulus migratorius）＋子午沙鼠为主的弃耕地型;（6）以褐家鼠（Rattus norvegicus）为主的城镇型。从原始荒漠到城镇居民区的环境梯度变化中,鼠类群落多样性指数呈上升趋势（1．1053～1．2744）,到农田达到最大,农田到居民区则略有下降;均匀性随各群落生境类型不同,变化无规律性（0．6423≤J≤0．9207）;优势度则呈下降趋势（0．4176～0．3368）。生境差异、植被盖度和人为干扰强度对鼠类群落多样性均有一定影响。     

山东五莲山植物群落结构及物种多样性

五莲山自然保护区地处鲁东南沿海地区,为全面了解其群落结构组成及物种多样性,作者进行了野外调查,共获得11个标准样方,面积6 600 m²。样方内记录到高等植物52科141种。该保护区地带性植被为常绿—落叶针阔叶天然次生混交林、落叶阔叶林,主要森林植被为赤松—板栗群落(Pinus densiflora-Castanea mollissima community)、麻栎—赤松群落(Quercus acutissima-Pinus densiflora community)、赤松—杜鹃群落（P. densiflora-Rhododendron simsii community）、麻栎—杜鹃群落(Q. acutissima-Rhododendron simsii community)。样方数据显示该区域木本植物种类不是很丰富,但植物群落结构复杂,具有明显的生境异质性,其多样性指数乔木层＜木本层＜灌木层。作者认为影响该保护区核心区多样性的最显著特征应该为海拔和坡度,而人为干扰会严重影响外围保护区植被类型及其物种多样性。整体上看,本区域正处于群落演替早期,种间竞争尚不充分,物种多样性偏低。     

陆地植物群落物种多样性演替研究进展

植物群落物种多样性在不同梯度上,其变化规律不一致.物种多样性与纬度呈反相关关系,与水分关系密切,表现出不同变化规律,与海拔主要表现为反相关关系和中间高度膨胀规律.土壤盐度、水分、肥力对物种多样性也有影响.在不同演替阶段物种多样性出现不同变化规律,群落结构最复杂的演替阶段,物种多样性最高.     

广西流星天坑植物群落结构与多样性

以广西乐业流星天坑为研究对象,在流星天坑腰部与底部设置样地,采用样方法调查冠层树种及林下植物群落;并用数量生态学的方法分析了天坑植物群落的组成、结构与物种多样性,探讨其生境关联。结果表明:(1)在天坑调查的样地中,胸径大于10cm的冠层树种个体60株,隶属于13科、17属、18种,个体密度约为188株/hm2。林下植物种群共记录到94株个体,隶属于28科、38属、43种,个体密度为23 500株/hm2。群落物种多样性较丰富,Shannon-Wiener多样性指数和均匀度指数均较高;冠层树种的科属多样性很高,体现出群落组成的古老和隔离性质。(2)樟科是流星天坑植物群落的优势科,在群落冠层包含4个种14株个体,在林下包含3个种,7株个体,其中2种与群落冠层共有;群落的林下层含物种数较多的科包括大戟科(4种)、菊科(3种)、凤尾蕨科(3种)、鳞毛蕨科(3种),但天坑植物群落中种群水平的优势现象不明显。(3)林下植物包含了各种生长型,以灌木数量最多,禾草类植物数量最少,乔木的幼苗也较少,体现出天坑的生境提供了较丰富的资源生态位,同时也表明乔木的幼苗更新不良。(4)流星天坑大树数量比例高,在样地中记录到的60株个体中,最小胸径为17.0cm,最大胸径104.0cm,胸径30cm的大树共34株,占全部立木比例56.6%,体现出天坑森林群落的原始性并且未受到干扰破坏。(5)双向指示种分析表明,广西乐业天坑林下植物对生境的响应更为敏感,但无论冠层还是林下层其现状分布并不能完全把坑腰和坑底两种生境分离。该研究结果为深入开展天坑这种特殊生境下植物种群以及群落的发生、演替和生态适应性的研究提供了基础数据及理论依据。     

Inorganic Species Distribution and Microbial Diversity within High Arctic Cryptoendolithic Habitats

Cryptoendolithic habitats in the Canadian high Arctic are associated with a variety of microbial community assemblages, including cyanobacteria, algae, and fungi. These habitats were analyzed for the presence of metal ions by sequential extraction and evaluated for relationships between these and the various microorganisms found at each site using multivariate statistical methods. Cyanobacteria-dominated communities exist under higher pH conditions with elevated concentrations of calcium and magnesium, whereas communities dominated by fungi and algae are characterized by lower pH conditions and higher concentrations of iron, aluminum, and silicon in the overlying surfaces. These results suggest that the activity of the dominant microorganisms controls the pH of the surrounding environment, which in turn dictates rates of weathering or the possibility for surface crust formation, both ultimately deciding the structure of microbial diversity for each cryptoendolithic habitat.     

中国沙拐枣属天然群落特征及其物种多样性研究

根据野外调查资料,应用生物多样性的原理和方法计测了群落的物种丰富度指数(R0、R1)、物种多样性指数(H′、D)、均匀度指数(E)以及优势度指数(C)以分析中国沙拐枣属天然群落的群落学特征。结果表明(1)中国沙拐枣属天然群落组成成分简单,共出现种子植物91种,分属22科62属,科属组成较为分散;生活型组成中1年生植物种类多,数量大,占总数的35.16%;沙拐枣属天然群落的垂直结构明显;(2)多样性分析表明,中国沙拐枣属天然群落物种组成单一,结构简单,其中群落多样性最低分别为塔克拉玛干沙拐枣(Calligonum roborowskii)群落和沙拐枣(C.mongolicum)(若羌)群落。群落多样性最高分别为沙拐枣(C.mongolicum)(采南)群落、小沙拐枣(C.pumilum)群落和艾比湖沙拐枣(C.ebi-nuzicum)群落。不同沙拐枣属植物所形成的群落差异主要表现在物种组成以及物种多样性水平,这种差异表现主要是1年生和多年生草本植物的物种多样性。(3)丰富度指数和物种多样性指数表现出基本一致的变化趋势,而生态优势度指数则表现相反的趋势。物种的丰富度指数和多样性指数与群落的结构以及立地环境条件等有密切的关系,结构复杂的群落较其它群落的多样性指数高,但由于特殊生境所形成的单优群落物种多样性指数则较低。     

曲阜师范大学校园蜘蛛种类组成、群落结构与物种多样性

2006年春季,通过对山东省曲阜师范大学校园蜘蛛随机采样调查,共采集到蜘蛛标本336个,经鉴定统计,共发现曲阜师范大学校园蜘蛛46种,隶属2亚目,16科,37属。其中山东新记录种4种,有2种标本仅鉴定到属。校园蜘蛛物种多样性高,Shannon多样性指数为4．65,Simpson多样性指数为0．94。     

The Relationship between Species Diversity and Genetic Structure in the Rare Picea chihuahuana Tree Species Community,Mexico

Species diversity and genetic diversity, the most basic elements of biodiversity, have long been treated as separate topics, although populations evolve within a community context. Recent studies on community genetics and ecology have suggested that genetic diversity is not completely independent of species diversity. The Mexican Picea chihuahuana Martínez is an endemic species listed as “Endangered” on the Red List. Forty populations of Chihuahua spruce have been identified. This species is often associated with tree species of eight genera in gallery forests. This rare Picea chihuahuana tree community covers an area no more than 300 ha and has been subject of several studies involving different topics such as ecology, genetic structure and climate change. The overall aim of these studies was to obtain a dataset for developing management tools to help decision makers implement preservation and conservation strategies. However, this unique forest tree community may also represent an excellent subject for helping us to understand the interplay between ecological and evolutionary processes in determining community structure and dynamics. The AFLP technique and species composition data were used together to test the hypothesis that species diversity is related to the adaptive genetic structure of some dominant tree species (Picea chihuahuana, Pinus strobiformis, Pseudotsuga menziesii and Populus tremuloides) of the Picea chihuahuana tree community at fourteen locations. The Hill numbers were used as a diversity measure. The results revealed a significant correlation between tree species diversity and genetic structure in Populus tremuloides. Because the relationship between the two levels of diversity was found to be positive for the putative adaptive AFLP detected, genetic and species structures of the tree community were possibly simultaneously adapted to a combination of ecological or environmental factors. The present findings indicate that interactions between genetic variants and species diversity may be crucial in shaping tree communities.     

阿拉善雅布赖风沙区荒漠植物群落结构和物种多样性研究

根据阿拉善雅布赖风沙区30个样地的调查资料,对该区荒漠植物群落物种多样性进行分析.结果表明:雅布赖风沙区天然植被物种组成简单,以旱生、盐生或超旱生的小灌木和多年生草本植物占主导地位,体现出荒漠半荒漠和草原化荒漠植物群落的特点.群落优势层片为灌木层,其物种组成以矮化的半灌木和小灌木为主(占41%～90%),受环境变化的影响较小,结构比较稳定;草本层片组成中以多年生草本为主,但一年生草本的数量却占到81.5%～98.8%,为不稳定层片.雅布赖风沙区荒漠植物群落多样性数量特征值差异较大,在植被生态建设时应关注不同生活型植被的防护效应与当地大风和沙尘暴在发生时间上的匹配性,针对半灌木、小灌木和多年生草本覆盖特有的防风性能,重视灌木和多年生草本的恢复与建设,以取得抵抗风沙、稳定当地生态环境的效果.     

珍贵药材黄花倒水莲的群落结构及物种多样性研究

黄花倒水莲系华南民间常用且珍贵中药材。采用样方调查法对福建省三明地区黄花倒水莲群落的植物组成、群落结构和物种多样性进行了分析。结果表明,在26个样方、共计2600m2的样地内,群落有维管植物89科167属205种。种子植物属的区系成分划分为12个分布型和8个变型,热带性分布属稍占优势,占总属数的57.85%;温带性成分占总属数的40.7%。生活型谱分析显示群落包括藤本在内的高位芽植物占总种数的58.53%,其中以小高位芽和矮高位芽植物占优势;地面芽和地上芽占较大比例,以蕨类植物和多年生草本植物为主,地下芽和1年生植物很少。群落垂直结构分为乔木层、灌木层和草本层。物种丰富度指数、Simpson指数、Shannon-Wiener指数和Pielou均匀度指数分析表明:群落垂直结构多样性特点为草本层>灌木层>乔木层>层外层,草本层的各项多样性指数均显著大于其他层次。为黄花倒水莲人工栽培选择适生环境提供参考,提出了开发利用和资源保护的建议。     

Effects of Species Diversity on Establishment and Coexistence: A Phylloplane Fungal Community Model System

A model system was devised, evaluating the influence that species diversity (species richness) has on fungal establishment and coexistence. Seven members of the fungal phylloplane community of Vaccinium macrocarpon (American cranberry) were selected to assess how species diversity affected development and coexistence of another community member, Pestalotia vaccinii. Pestalotia was engaged in competitive interactions on 1% Malt Extract Agar (MEA) petri dishes with each of the seven individual saprotrophs (two-way interaction), in random combinations with three of the seven saprotrophs (four-way interaction), and in random combinations with five of the seven saprotrophs (six-way interaction). The saprotrophic fungi used in this study were Aspergillus sp., Alternaria alternata, Cladosporium cladosporoides, Curvularia lunata, Epicoccum purpuracens, Penicillium sp., and Pithomyces chartarum. We hypothesized that species diversity would have a significant impact on the establishment and coexistence of Pestalotia vaccinii in culture. In an effort to minimize density-dependent effects, the number of viable spores employed in the three types of interactions was kept constant. Target spore concentrations of 50 viable spores of P. vaccinii and 50 saprotroph spores were used, regardless of the number of species involved in the interaction. This proved to be a very important factor in the experiment. As our results show, species diversity had little or no effect on the establishment and coexistence of Pestalotia vaccinii; however, spore density played an extremely important role in the establishment and development of fungal propagules in our model.     

民勤连古城自然保护区群落结构和物种多样性特征分析

通过物种多样性指数、林地承载力以及土壤水分等指标对民勤连古城自然保护区荒漠群落的结构和物种多样性以及影响因子进行了研究。结果表明:(1)群落的优势层片为灌木层,其物种组成和结构比较稳定,受环境变化的影响较小,而草本层为不稳定层片;(2)荒漠群落的物种多样性指数均偏低,生态优势度较高,群落的生态功能主要由优势种群或建群种群实施,在无外界干扰情况下,优势种群或建群种群的稳定性可以揭示群落的稳定性;(3)土壤水分是影响群落结构的主导因子,而降水是土壤水分的主要来源,对群落结构具有显著影响。土壤异质性对群落结构同样具有显著影响,是第二主导因子,其物种多样性指数为黏性土壤>灰棕荒漠土>风沙土;(4)群落物种多样性与其林地承载力无一定规律的相关性,灌木层片中,二者呈对数相关(y=64.787ln(x) 214.04,R2=0.829,P<0.01),能够比较科学地揭示物种多样性与林地承载力之间的关系,而草本层中二者呈幂指数相关(y=0.3198e6.1654x,R2=0.6999,P<0.01),反映了林地承载力受环境因子变化的影响。     

山西南部脱皮榆群落生态特征及其物种多样性的研究

选择脱皮榆群落分布较为集中的霍山、中条山等2个地段,设计7个样地,用样方法进行调查,共做样方585个。分析了脱皮榆群落的种类组成、区系特点、群落外貌、垂直结构等群落学特征,并对该群落的环境概况进行分析,计测了不同地段群落的重要值指标和不同层次上的Shannon-Wiener指数、Simpson指数和Pielou指数。结果表明,脱皮榆主要分布于海拔1100-1650m的中海拔山地。群落组成种类约156种,北温带分布属占优势,显示了脱皮榆群落具有北温带性质。高位芽和一年生植物种类多,显示了脱皮榆群落分布区域夏季水热条件良好,冬季漫长、寒冷、干旱的气候特点。乔木层平均高度约13m,多样性指数H为1．0260一1,5907;灌木层H值0．9983—2．4478;草本层H值为0．9047—3.0621。研究为脱皮榆可持续利用和保护提供了有益的参考。