Sampling strategies for the assessment of tree species diversity

Abstract. This paper aims at proposing efficient vegetation sampling strategies. It describes how the estimation of species richness and diversity of moist evergreen forest is affected by (1) sampling design (simple random sampling, random cluster sampling, systematic cluster sampling, stratified cluster sampling); (2) choice of species richness estimators (number of observed species vs. non-parametric estimators) and (3) choice of diversity index (Simpson vs. Shannon). Two sites are studied: a 28-ha area situated in the Western Ghats of India and a 25-ha area located at Pasoh in Peninsular Malaysia. The results show that: (1) whatever the sampling strategy, estimates of species richness depend on sample size in these very diverse forest ecosystems which contain many rare species; (2) Simpson's diversity index reaches a stable value at low sample sizes while Shannon's index is affected more by the addition of rare species with increasing sample size; (3) cluster sampling strategies provide a good compromise between cost and statistical efficiency; (4) 300 - 400 sample trees grouped in small clusters (10–50 individuals) are enough to obtain unbiased and precise estimates of Simpson's index; (5) the local topography of the Western Ghats has a major influence on forest composition, the steep slopes being richer and more diverse than the ridges and gentle slopes; (6) stratified cluster sampling is thus an interesting alternative to systematic cluster sampling.     

自然保护区在保护生物多样性中的作用和意义

本文从理论上论述了自然保护区在生物多样性保护中的重要作用,并指出建立自然保护区是保护生物多样性的最有效措施。1.在自然保护区里,基本的生态过程和生命系统得以维持;2.自然保护区提供了物种生存和进化的场所;3.在自然保护区里,不仅能保护生存其中的已知物种;而且能保护所有的未知物种;4.在自然保护区里?能够保护足够大的种群和完整的种群结构;5.自然保护区的试验区是进行生态、遗传和进化等学科研究的理想基地。 基于野外调查的资料,本文分析了云南所建立的自然保护区在保护国家重点保护植物中的作用。云南分布有154种国家第一批重点保护植物。130余种分布于在各自然保护区中而得到了保护;第二批国家重点保护植物中的192种分布于云南,其中104种分布于各自然保护区中而得到了保护。 本文还对云南自然保护区的现状和管理状况进行了分析,指出了加强对自然保护区管理的迫切性。     

井冈山稀有濒危植物区系探讨

本文分析了井冈山稀有濒危植物39个种的地理分布和35个属的分布区类型及其区系特征,并认为:①稀有濒危植物的古老成份,反映了井冈山自侏罗纪以来地史与气候比较稳定,植物区系区的,演化具有一定的连续性;泥盆纪至侏罗纪可能是井冈山植物区系发生的重要时期。②稀有濒危植物的区系特点是,现代植物区系的种、属成份与华南联系紧密,与华东次之;区系的起源与古热带区系有重要关系。③井冈山特有种的形成可能是生态分异成因多于历史成因,并且温带性物种在井冈山的生态分异比热带性物种更趋强烈。     

广东乳阳山地广东松、长苞铁杉原生林的结构特征和动态分析

对乳阳林区亚热带山地广东松(Pinus kwangtungensis)、长苞铁杉(Tsuga longibracteata)原生林及其与阔叶树的混交林结构特征和动态作了论述和分析,并从森林群落演替的观点出发提出了保护和利用的建议。     

Vegetation of Pande and Kiono Coastal forests,Tanzania

East African coastal forests possess considerable botanical importance as an area of high plant endemicity, but are little known ecologically. Quantitative botanical sampling techniques have been used to determine vegetation communities in Pande and Kiono coastal forests, Tanzania. Data from 76 quadrats established in six transects (three in each forest) and containing a total of 146 plant species have been classified using TWINSPAN. Seven species-associations and four sample-associations are recognised. Undisturbed forest supports six species-associations which are rich in plant species of restricted distribution, and these differ between the sites studied. Forest heavily disturbed by man supports one species-association composed of more generalist forest species and this association is similar between sites. Variation in vegetation types of undisturbed forests appears to be caused by edaphic conditions, rainfall and degree of exposure. Variation in the vegetation of disturbed forests appears to be controlled by the intensity of forest disturbance. Heavy human disturbance of coastal forests reduces their biodiversity values as plant-diversity and the habitats of rare plant species are lost.     

Habitat restriction in Mammillaria pectinifera,a threatened endemic Mexican cactus

Abstract. This study deals with the habitat restriction of Mammillaria pectinifera, a threatened cactus species, confined to a few low density localities of the Tehuacán valley in tropical Mexico. We analysed the patterns of presence/absence of M. pectinifera in relation to the presence/absence of 48 other plant species, and the variation of environmental factors in 120 sampling plots. A Principal Components Analysis revealed a clear segregation between plots with and without individuals of M. pectinifera. A classification analysis resulted in four groups: two with low prevalence and two with high prevalence of M. pectinifera. Paired comparisons between plots with and without M. pectinifera allowed the characterization of its patterns of occurrence related to the variation of environmental factors. M. pectinifera was found on deep alkaline soils with relatively high surface stoniness and high water retention capacity, showing low species richness compared with plots where it was absent. The limited distribution of M. pectinifera in the Tehuacán Valley seems to be related to particular requirements of this species, being restricted to certain suitable habitat patches. Nevertheless, it is likely that other aspects, such as poor dispersal and establishment abilities, or biotic interactions could be associated with the observed patterns.     

Bootstrap confidence intervals for adaptive cluster sampling

Consider a collection of spatially clustered objects where the clusters are geographically rare. Of interest is estimation of the total number of objects on the site from a sample of plots of equal size. Under these spatial conditions, adaptive cluster sampling of plots is generally useful in improving efficiency in estimation over simple random sampling without replacement (SRSWOR). In adaptive cluster sampling, when a sampled plot meets some predefined condition, neighboring plots are added to the sample. When populations are rare and clustered, the usual unbiased estimators based on small samples are often highly skewed and discrete in distribution. Thus, confidence intervals based on asymptotic normal theory may not be appropriate. We investigated several nonparametric bootstrap methods for constructing confidence intervals under adaptive cluster sampling. To perform bootstrapping, we transformed the initial sample in order to include the information from the adaptive portion of the sample yet maintain a fixed sample size. In general, coverages of bootstrap percentile methods were closer to nominal coverage than the normal approximation.     

Vitellogenin in rare minnow (Gobiocypris rarus): identification and induction by waterborne diethylstilbestrol

Rare minnow (Gobiocypris rarus) is a tiny Chinese carp that has a short life cycle and is easily cultured in the laboratory. In this study, juvenile rare minnows were exposed to waterborne diethylstilbestrol (DES) at 0.05, 0.5 and 5 microg/l in laboratory aquaria. After exposure for 4, 8, 13 and 21 days, juvenile fish were collected and vitellogenin (Vtg) was measured in whole body homogenates. Native and SDS electrophoresis followed by Western blotting were performed for Vtg identification, and a non-competitive ELISA was developed. In the DES exposure groups (0.5 and 5 microg/l DES), Vtg appeared after 4 days, increased significantly after 8 days and reached a maximum on day 13. Further, a significant increase in the hepatosomatic index (HSI) was found in the 5 microg/l DES exposure group after 21 days. These results indicate that rare minnow provides a good model for assessing endocrine disruption by environmental estrogens.     

广东始兴南山自然保护区的植物资源及珍稀植物

对南山自然保护区的初步调查结果显示,区内有野生维管植物179科565属1039种,国家二级野生保护植物9种,其他珍稀濒危的种类7种。由此可见,南山自然保护区植物资源极其丰富,野生维管植物及珍稀保护植物是其重要组成部分。其中野生维管植物资源种类繁多,蕴藏量较大,而且不少种类具有开发和可持续利用的价值,具有巨大的经济价值和生态价值。     

Contribution of rare and common variants determine complex diseases—Hirschsprung disease as a model

Finding genes for complex diseases has been the goal of many genetic studies. Most of these studies have been successful by searching for genes and mutations in rare familial cases, by screening candidate genes and by performing genome wide association studies. However, only a small fraction of the total genetic risk for these complex genetic diseases can be explained by the identified mutations and associated genetic loci. In this review we focus on Hirschsprung disease (HSCR) as an example of a complex genetic disorder. We describe the genes identified in this congenital malformation and postulate that both common ‘low penetrant’ variants in combination with rare or private ‘high penetrant’ variants determine the risk on HSCR, and likely, on other complex diseases. We also discuss how new technological advances can be used to gain further insights in the genetic background of complex diseases. Finally, we outline a few steps to develop functional assays in order to determine the involvement of these variants in disease development.