武夷山大安源甜槠常绿阔叶林群落物种组成及多样性分析

采用相邻格子样方法对武夷山大安源甜槠〔Castanopsis eyrei(Champ.ex Benth.)Tutch.〕常绿阔叶林群落的物种组成及物种多样性进行了研究,并分析了群落的种-面积曲线以及样方面积与物种多样性的关系。结果表明:在面积4 800 m2的样方中共记录维管植物31科57属97种,其中乔木78种、灌木8种、草本植物5种、藤本植物6种;乔木主要为常绿树种,落叶树种仅10种;优势科为壳斗科(Fagaceae)、杜鹃花科(Ericaceae)、杜英科(Elaeocarpaceae)和山茶科(Theaceae)等,优势属为栲属〔Castanopsis(D.Don)Spach〕、杜鹃属(Rhododendron Linn.)和杜英属(Elaeocarpus Linn.);优势树种为甜槠、马银花〔Rhododendron ovatum(Lindl.)Planch.〕、鹿角杜鹃(R.latoucheae Franch.)和薯豆(Elaeocarpus japonicus Sieb.et Zucc.)等,其中甜槠的相对胸高断面积达64.93%,重要值也最高(25.70%),在群落中具有明显的优势地位。群落中胸径小于5 cm的乔木个体数量占76.88%,径级越高个体数量越少。南坡样方的Simpson指数和Shannon-Wiener指数均高于北坡,显示该群落南坡的物种多样性高于北坡。该群落的种-面积曲线拟合方程为y=21.836ln(x)-87.287(R2=0.990 2),且随样方面积的增加,物种数量、Shannon-Wiener指数和Pielou指数呈增加且趋于稳定的趋势,总体上调查样方面积应设置在2 000 m2以上。综合分析结果说明:武夷山大安源甜槠常绿阔叶林的物种组成较丰富、物种多样性水平较高;光照条件是导致该群落南坡多样性大于北坡的主要环境因素。     

山西霍山植物群落种-面积曲线与物种多样性的关系

采用标准样方调查法,对霍山植物群落的物种数、面积和物种多样性之间的关系进行了研究.结果表明:种(对数)-面积(对数)曲线在各海拔处的R2值较种-面积曲线和种-面积(对数)曲线大,中海拔处的平均物种数最多,群落Margalef丰富度指数(R)和Shan-non-Wiener多样性指数(H')也最大,而Jaccard系数(J)最小.各海拔样地物种数的观察值与种-面积曲线和种-面积(对数)曲线在各海拔样地物种数的预测值接近.     

破碎化次生林斑块面积及栖息地质量对繁殖鸟类群落结构的影响

于1998～2000年夏季。运用GPS定位系统确定了12块面积范围为6．5～112．8hm。的彼此隔离的森林斑块。比较了斑块面积和栖息地质量对繁殖鸟类群落结构的影响。结果表明：不同面积斑块中繁殖鸟类的群落结构有所差异。各斑块所容纳的繁殖鸟类的物种数从4种到26种不等。鸟类物种数随着斑块面积的增大而增多。不同鸟类对斑块面积的反应并不相同,耐边缘种偏爱面积较小的斑块。而非边缘种偏爱在大面积的斑块中繁殖。斑块栖息地质量也是影响鸟类群落结构的重要因素,质量好的斑块包容的鸟类物种较多。鸟类物种丰富度与斑块质量的相关性(R2=0．67)小于与斑块面积的相关性(R2=0．88)。各斑块中的鸟类群落结构在不同年份间比较相似。栖息地破碎化不但缩小了栖息地面积。同时也不同程度地降低了栖息地的质量。从而消极地影响着鸟类群落结构的稳定性和鸟类的物种多样性。     

松嫩平原破碎化羊草草甸退化演替系列植物多样性的空间格局

物种多样性格局是国际生物多样性科学前沿领域热点问题.本文以松嫩平原破碎化羊草草甸退化演替系列(6种植物群落、144个斑块)为研究对象,系统地探讨了其α、β和γ多样性空间格局及其机理.结果表明:在羊草草甸退化演替系列中共发现87种植物,但没有一种能分布于所有斑块;羊草+鸡儿肠群落或羊草群落的α、β和γ多样性较高,多稀有种和特有种;碱地肤群落最低,少稀有种,无特有种;γ多样性与α多样性显著正相关,但与β多样性无相关性.各植物群落的α多样性与单个斑块面积呈显著幂函数关系,β多样性(相似性指数Sjk)仅羊草+鸡儿肠群落呈显著幂函数关系;斑块平均面积和总面积与α、γ多样性呈显著正相关,与β多样性无相关性.群落的物种丰富度越高,稀有种和特有种就越多,物种在局域斑块上灭绝的可能性越大;β多样性在物种多样性格局中的重要性与生境破碎化程度有关.     

海南岛霸王岭两种典型热带季雨林群落特征

热带季雨林为海南岛的隐域性植被类型,分布在与热带低地雨林相似的海拔范围但生境条件较差的局部地段,在旱季其大部分的乔木种类和个体都会落叶.海南岛霸王岭林区分布着海南岛最为典型且大都保存较为完好的热带季雨林原始林,按照其优势树种可划分为海南榄仁(Terminalia hainanensis)季雨林和枫香(Liquidambar formosana)季雨林两种群落类型.通过对霸王岭林区两种典型的热带季雨林老龄林群落的样地调查,比较分析了其物种组成、大小结构、多样性、季相变化等特征.结果表明:海南岛热带季雨林群落中物种优势度明显,具有明显的标志种--海南榄仁和枫香.海南榄仁群落具有较高的灌木物种丰富度、个体多度及较低的乔木物种丰富度、个体多度和多样性;海南榄仁群落在小径级和低高度级中具有较高的植物个体多度,同时在低高度级中具有较低的物种丰富度,但其它径级和高度级两个群落物种丰富度及个体多度差异均不显著;除灌木落叶物种丰富度海南榄仁群落显著高于枫香群落外,其余各生长型落叶物种丰富度及个体多度两个群落之间均无显著差异;在具刺木质藤本物种丰富度和个体多度上海南榄仁群落与枫香群落差异不显著,但乔木、灌木和木本植物具刺物种丰富度及个体多度海南榄仁群落均显著高于枫香群落.总体来看,海南榄仁群落比枫香群落的季雨林特征明显,是海南岛最为典型的季雨林群落类型.     

井冈山自然保护区福建柏群落的研究

对井冈山福建柏(Fokienia hodginsii)群落4个样地的物种组成、区系成分和物种多样性进行了统计和分析.结果表明:该群落有维管植物32科43属59种,其中蕨类植物有4科4属5种,裸子植物3科3属3种,被子植物25科36属51种.区系分析显示该植物区系起源古老,地理成分复杂,以温带性成分为主,热带亚热带成分占有较大比例.群落为复层异龄结构,类型有福建柏 甜槠(Castanopsis eyrei)群落、福建柏 猴头杜鹃(Rhododendronsimiarum) 甜槠群落.群落物种多样性指数较高,各样地间多样性指数变幅不大;福建柏群落的4种多样性指数基本表现出相同的趋势,福建柏群落物种多样性在群落不同层次的变化规律为:灌木层>乔木层>草本层.     

秦岭南坡松栎林群落演替过程中物种组成及多样性动态分析

为揭示秦岭南坡植物群落演替与物种多样性之间的复杂关系,采用空间代替时间的方法在秦岭南坡油松林、松栎混交林和锐齿栎林群落典型分布区域设置45个样地进行了群落学调查,统计分析了油松林→松栎混交林→锐齿栎林这一演替序列过程中草、灌、乔3层的物种组成和α物种多样性动态。结果表明:(1)秦岭南坡油松林、松栎混交林和锐齿栎林3种群落共有维管植物312种,隶属于73科183属,其中草本植物136种,灌木(含木质藤本)98种,乔木78种;油松林群落包含52科117属190种,松栎混交林群落含有60科95属129种,锐齿栎林群落则为50科109属178种。(2)沿油松林→松栎混交林→锐齿栎林群落演替序列,草本层物种均匀度和物种多样性显著降低,物种丰富度呈"V"形变化趋势;灌木层物种丰富度、均匀度以及物种多样性均无显著差异;乔木层物种多样性呈明显的单峰型变化,其中松栎混交林群落物种多样性指数最高。研究表明,秦岭南坡松栎林群落物种多样性随演替进展总体上呈现单峰型变化,与中期物种多样性假说一致;物种多样性可能仅仅是群落稳定的一个基础或前提条件。     

不同演替阶段东方水韭群落特征初步研究

采用"空间代替时间"的方法,对处于不同演替阶段的东方水韭(Isotes orientalis H. Liu et Q. F. Wang)群落进行了物种组成、群落生态学数量特征、物种多样性及繁殖方式的比较分析,结果表明,在演替初期,群落的多样性(物种丰富度、Shannon-Wiener指数、Pielou均匀度指数和β多样性指数)最低,群落中东方水韭的多度、盖度、重要值和生态位宽度均最大,是明显的优势种;演替中期,东方水韭的多度、盖度、重要值和生态位宽度降低,但群落的物种多样性最高,是东方水韭的顶极群落;演替后期,群落中东方水韭的多度、盖度、重要值和生态位宽度均最低,多年生草本植物细叶芒(Miscanthus sinensis Anderss. )和菰[Zizania latifolia (Griseb. ) Turcz. ex Stapf]等逐渐占据重要地位.随群落的演替,群落中营无性/营养繁殖方式的物种数量逐渐增加,群落的繁殖策略由有性繁殖为主转为以无性/营养繁殖为主.研究结果显示,在东方水韭群落演替过程中,群落物种组成的改变、物种多样性的提高、物种繁殖策略的变化以及生境中生化,可能是导致东方水韭种群衰退的主要原因.     

林窗对川西周公山柳杉人工林林下物种多样性的影响

采用典型样地法,以川西周公山柳杉人工林5种不同大小的林窗为研究对象,以林下非林窗为对照,研究了不同大小的林窗对柳杉人工林物种多样性的影响,同时分析了不同梯度林窗下林窗中心、林窗边缘、及林下群落的物种组成、物种多样性的变化情况。结果表明:(1)在所调查的18个样地231个样方中共记录到维管束植物141种,隶属于76科113属;随着林窗面积的增大,群落各层次的物种数呈现出先升高后降低的趋势,灌木层物种数在各林窗梯度上表现为林缘林下林窗中心,草本层物种数在各林窗梯度上表现为林缘林窗中心林下。(2)不同林窗优势种及其重要值不同,即在小林窗内,优势种为柳杉和野桐,其重要值之和高达0.292 3;在大林窗内,杉木及亮叶桦为群落优势物种,群落内出现大量其更新幼苗。(3)不同大小的林窗表现为灌木层物种丰富度指数(D)、Shannon-Wienner指数(H)、和Pielou均匀度指数(Jsw)值在400~450 m2面积的大林窗内达到一个均优水平,草本层物种的多样性在面积为100~150m2的小林窗内达到较高水平;不同梯度的林窗各层次群落D、H值整体表现为林缘林窗中心林下。研究认为:林窗的存在会改变群落物种组成,提高群落物种多样性水平,并且大林窗(400~450m2)更利于柳杉人工林林下树种更新及物种多样性的提高。     

四川大巴山米心水青冈（Fagus engleriana）群落的物种多样性特征

四川省大巴山处于秦岭南部的北亚热带,水青冈属植物分布较集中.该处米心水青冈(Fagus engleriana)林分布面积较大,生长良好,保存相对完好,具有重要的地域代表性.分析了米心水青冈群落的物种组成、区系地理成分、物种多样性以及群落自身特征与物种多样性的灰色关联度,得到以下主要结果:(1)在4个样地28个10m×10m群落样方中,一共记录到维管束植物197种,隶属140属、74科. 群落乔木层物种主要由壳斗科、蔷薇科、杜鹃花科、桦木科、槭树科等科组成;灌木层物种主要由蔷薇科、忍冬科、杜鹃花科等科组成;草本层主要由莎草科、菊科、百合科等科植物组成.(2)地理区系成分中,温带成分分别占群落总属数、总种数的65.38%和64.32%,处于主导地位;热带和亚热带成分占总属数、总种数的23.85%、24.32%.(3)群落中物种数目-多度在不同的层次变化趋势不同.(4)群落的物种丰度以灌木层最高、乔木层最低.Shannon指数、Simpson指数、均匀度指数以草本层最高、灌木层最低.(5)乔、灌、草3层的物种多样性均受到乔、灌两层植物的多度与盖度的影响,说明群落自身的特征与群落物种多样性是紧密相关的.     

Regional patterns of diversity and estimates of global insect species richness

The total number of insect species in the world is an important if elusive figure. We use a fresh approach to estimate global insect species richness, based on biogeographic patterns of diversity of well or better documented taxa. Estimates generated by various calculations, all variations on a theme, largely serve to substantiate suggestions that insect species are likely to number around 10 million or less.     

Assessing the accuracy of species distribution models to predict amphibian species richness patterns

1. Evaluating the distribution of species richness where biodiversity is high but has been insufficiently sampled is not an easy task. Species distribution modelling has become a useful approach for predicting their ranges, based on the relationships between species records and environmental variables. Overlapping predictions of individual distributions could be a useful strategy for obtaining estimates of species richness and composition in a region, but these estimates should be evaluated using a proper validation process, which compares the predicted richness values and composition with accurate data from independent sources. 2. In this study, we propose a simple approach to estimate model performance for several distributional predictions generated simultaneously. This approach is particularly suitable when species distribution modelling techniques that require only presence data are used. 3. The individual distributions for the 370 known amphibian species of Mexico were predicted using maxent to model data on their known presence (66,113 presence-only records). Distributions were subsequently overlapped to obtain a prediction of species richness. Accuracy was assessed by comparing the overall species richness values predicted for the region with observed and predicted values from 118 well-surveyed sites, each with an area of c. 100 km(2), which were identified using species accumulation curves and nonparametric estimators. 4. The derived models revealed a remarkable heterogeneity of species richness across the country, provided information about species composition per site and allowed us to obtain a measure of the spatial distribution of prediction errors. Examining the magnitude and location of model inaccuracies, as well as separately assessing errors of both commission and omission, highlights the inaccuracy of the predictions of species distribution models and the need to provide measures of uncertainty along with the model results. 5. The combination of a species distribution modelling method like maxent and species richness estimators offers a useful tool for identifying when the overall pattern provided by all model predictions might be representing the geographical patterns of species richness and composition, regardless of the particular quality or accuracy of the predictions for each individual species.     

Global and regional tree species diversity

Aims Understanding tree species richness at a global scale and the origin and maintenance of patterns of tree species richness across the world is crucial to preserving tree species diversity. The recently published global tree database (i.e. GlobalTreeSearch) is the only source with tree lists at both global and national scales. However, our review and assessment show that many species included in GlobalTreeSearch are not tree species. In addition, several thousands of tree species in the botanical literature have not been included in GlobalTreeSearch. The exact number of tree species in the world remains unknown. This study aims to correct errors with GlobalTreeSearch and to estimate the number of tree species in the world based on a large number of regional floras.     

Elevational species richness patterns for vascular plants on Mount Kinabalu, Borneo

Aim  We quantify the elevational patterns of species richness for all vascular plants and some functional and taxonomic groups on a regional scale on a tropical mountain and discuss some possible causes for the observed patterns.
Location  Mount Kinabalu, Sabah, Borneo.
Methods  A data base containing elevational information on more than 28,000 specimens was analysed for vascular plant distribution, taking into account sampling effort. The total species richness pattern was estimated per 300-m elevational interval by rarefaction analyses. The same methods were also applied to quantify species richness patterns of trees, epiphytes, and ferns.
Results  Total species richness has a humped relationship with elevation, and a maximum species richness in the interval between 900 and 1200 m. For ferns and epiphytes the maximum species richness is found at slightly higher elevations, whereas tree species did not have a statistically significant peak in richness above the lowest interval analysed.
Main conclusions  For the first time a rigorous estimate of an elevational pattern in species richness of the whole vascular plant flora of a tropical mountain has been quantified. The pattern observed depends on the group studied. We discuss the differences between the groups and compare the results with previous studies of elevational patterns of species richness from other tropical areas. We also discuss the methods used to quantify the richness pattern and conclude that rarefaction gives an appropriate estimate of the species richness pattern.     

Pteridophyte species richness in Andean forests in Bolivia

I assessed the magnitude and distribution of pteridophyte species richness on the eastern Andean slope in Bolivia based on 676 study plots of 400 m² each in forest habitats at 65 study sites. In total 755 species were recorded, including 426 (56%) epiphytes and 598 (79%) terrestrials, with 266 species (35%) recorded under both groups. Mean number of species per plot at a given site varied from 0 to 31.1 for epiphytes, 0 to 20.9 for terrestrials, and 0 to 47.9 for all species combined. The highest numbers of species recorded at a given study site were 110 epiphytes, 101 terrestrials, and 167 species in total. While overall there were more terrestrial than epiphytic species, at individual sites and plots the reverse was true, indicating that terrestrial species tended to be more patchily distributed than epiphytes. Despite high survey intensity, many species went unrecorded; the minimum estimate of total species richness obtained through extrapolation was 975 species overall, including 559 epiphytes and 880 terrestrials. A correlation analysis of species richness to 14 environmental parameters revealed a highly positive correlation to mean annual precipitation and bryophyte cover on tree branches (a proxy for air humidity). Significant correlations to other parameters (e.g. human impact, canopy height, etc.) reflected the covariance of these factors with precipitation and bryophyte cover. Despite a lack of data on the pteridophyte communities from much of the Bolivian Andes, it appears that in most of the countries, pteridophyte diversity can be protected by focussing the most humid parts of the Andean forests.     

Effects of species evenness can be derived from species richness – ecosystem functioning relationships

Although species richness effects on ecosystem functioning have been studied thoroughly in countless experiments, the effects of the other side of diversity – species evenness – remain less identified, especially at high species richness. Due to the large number of different model ecosystems that need to be created, the explanatory power of the experimental approach for evenness is indeed limited. We show here that experimental studies on the influence of species richness on ecosystem functions contain hidden information on the influence of species evenness. Both the effects of maximum and minimum evenness, and of a key set of intermediate evenness levels, can be derived from species richness – ecosystem function curves, and that for every richness level, by using communities with low species richness as the equivalent of highly uneven communities with higher richness. We show that evenness effects on ecosystem functioning have the same direction as richness effects, however with increasing effect sizes at higher richness levels. We validated our technique for a wide range of ecosystem functions and applied it to the species richness – community biomass data from an existing biodiversity experiment. Our approach could provide a fast and easy alternative to resource‐intensive experiments in which evenness is experimentally varied, as we can build on the elaborate existing literature on species richness to assess its effects.     

Patterns of richness across forest beetle communities—A methodological comparison of observed and estimated species numbers

1. Species richness is a frequently used measure of biodiversity. The compilation of a complete species list is an often unattainable goal. Estimators of species richness have been developed to overcome this problem. While the use of these estimators is becoming increasingly popular, working with the observed number of species is still common practice.
2. To assess whether patterns of beetle communities based on observed numbers may be compared among each other, we compared patterns from observed and estimated numbers of species for beetle communities in the canopy of the Leipzig floodplain forest. These patterns were species richness and the number of shared species among three tree species and two canopy strata.
3. We tested the applicability of the asymptotic Chao1 estimator and the estimate provided by the nonasymptotic rarefaction–extrapolation method for all tree species and both upper canopy and lower canopy. In the majority of cases, the ranking patterns of species richness for host tree species and strata were the same for the observed and estimated number of species. The ranking patterns of the number of species shared among host tree species and strata, however, were significantly different between observed and estimated values.
4. Our results indicate that the observed number of species under‐represents species richness and the number of shared species. However, ranking comparisons of published patterns based on the number of observed species may be acceptable for species richness but likely not reliable for the number of shared species. Further studies are needed to corroborate this conclusion. We encourage to use estimators and to provide open access to data to allow comparative assessments.

     

Deriving site-specific species pools from large databases

Defining the species pool of a community is crucial for many types of ecological analyses, providing a foundation to metacommunity, null modelling or dark diversity frameworks. It is a challenge to derive the species pool empirically from large and heterogeneous databases. Here, we propose a method to define a site-specific species pool (SSSP), i.e. the probabilistic set of species that may co-occur with the species of a target community. Using large databases with geo-referenced records that comprise full plant community surveys, our approach characterizes each site by its own species pool without requiring a pre-defined habitat classification. We calculate the probabilities of each species in the database to occur in the target community using Beals’ index of sociological favourability, and then build sample-based rarefaction curves from neighbouring records with similar species composition to estimate the asymptotic species pool size. A corresponding number of species is then selected among the species having the highest occurrence probability, thus defining both size and composition of the species pool. We tested the robustness of this approach by comparing SSSPs obtained with different spatial extents and dissimilarity thresholds, fitting different models to the rarefaction curves, and comparing the results obtained when using Beals co-occurrence probabilities or presence/absence data. As an example application, we calculated the SSSPs for all calcareous grassland records in the German Vegetation Reference Database, and show how our method could be used to 1) produce grain-dependent estimations of species richness across plots, 2) derive scalable maps of species richness and 3) define the full list of species composing the SSSP of each target site. By deriving the species pool exclusively from community characteristics, the SSSP framework presented here provides a robust approach to bridge biodiversity estimations across spatial scales.     

Patterns and causes of species richness: a general simulation model for macroecology

Understanding the causes of spatial variation in species richness is a major research focus of biogeography and macroecology. Gridded environmental data and species richness maps have been used in increasingly sophisticated curve‐fitting analyses, but these methods have not brought us much closer to a mechanistic understanding of the patterns. During the past two decades, macroecologists have successfully addressed technical problems posed by spatial autocorrelation, intercorrelation of predictor variables and non‐linearity. However, curve‐fitting approaches are problematic because most theoretical models in macroecology do not make quantitative predictions, and they do not incorporate interactions among multiple forces. As an alternative, we propose a mechanistic modelling approach. We describe computer simulation models of the stochastic origin, spread, and extinction of species’ geographical ranges in an environmentally heterogeneous, gridded domain and describe progress to date regarding their implementation. The output from such a general simulation model (GSM) would, at a minimum, consist of the simulated distribution of species ranges on a map, yielding the predicted number of species in each grid cell of the domain. In contrast to curve‐fitting analysis, simulation modelling explicitly incorporates the processes believed to be affecting the geographical ranges of species and generates a number of quantitative predictions that can be compared to empirical patterns. We describe three of the ‘control knobs’ for a GSM that specify simple rules for dispersal, evolutionary origins and environmental gradients. Binary combinations of different knob settings correspond to eight distinct simulation models, five of which are already represented in the literature of macroecology. The output from such a GSM will include the predicted species richness per grid cell, the range size frequency distribution, the simulated phylogeny and simulated geographical ranges of the component species, all of which can be compared to empirical patterns. Challenges to the development of the GSM include the measurement of goodness of fit (GOF) between observed data and model predictions, as well as the estimation, optimization and interpretation of the model parameters. The simulation approach offers new insights into the origin and maintenance of species richness patterns, and may provide a common framework for investigating the effects of contemporary climate, evolutionary history and geometric constraints on global biodiversity gradients. With further development, the GSM has the potential to provide a conceptual bridge between macroecology and historical biogeography.     

Testing for local species saturation with nonindependent regional species pools

Identifying the factors controlling local community structure is a central problem in ecology. Ecologists frequently use regression to test for a nonlinear saturating relationship between local community richness and regional species pool richness, suggesting that species interactions limit the number of locally coexisting species. However, communities in different regions are not independent if regions share species. We present a Monte Carlo test for whether an observed local-regional richness relationship is significantly different from that expected when regions are nonindependent and species interactions do not limit community membership. We illustrate this test with data from experimental microcosm communities. A conventional F -test suggests a significant saturating relationship between realized community richness and species pool richness. However, the Monte Carlo test fails to reject the null hypothesis that species interactions do not affect community richness. Strong species interactions do not necessarily set an absolute upper limit to the number of locally coexisting species.