生态系统的脆弱性与退化生态系统

生态系统的脆弱性是一个含义广泛的概念,是生态系统内固有的特性,脆弱性只能在干扰的状态下才显现出来．而干扰（包括自然干扰和人为干扰）又是引起退化生态系统的原因,种类的入侵和消亡、种类组成的变化、生态系统的多样性和稳定性、生产力、生态位的分化及生态系统小环境变化则是研究退化生态系统形成和恢复的重要内容,本文探讨脆弱性与退化生态系统诸方面的关系以及在植被恢复上的应用．     

山西蟒河自然保护区栓皮栎林的聚类和排序

本文用等级聚类、极点排序、主成分分析和对应分析等多元分析法, 对蟒河自然保护区的栓皮标(Quercus variabilis)林进与于了聚类和排序。等级聚类法将蟒河自然保护区的栓皮栎林划分为五个群丛, 极点排序、主成分分析和对应分析三种方法得出一致的结论, 并较好地反映了环境变化的梯度及植被变化的连续性。综合分析表明栓皮栎林是保护区内稳定的群落类型。     

Latitudinal comparison of altitudinal changes in forest structure,leaf-type,and species richness in humid monsoon Asia

A new template for mountain vegetation zonation along latitudinal gradients is proposed for examining geographical pattern of various forest attributes in humid monsoon Asia. The contrasting temperature regime in tropical and temperate mountains, i.e., the former is a non-seasonal, temperature-sum controlled environment, and the latter is a seasonal, low temperature limiting environment, leads to different altitudinal patterns of tree height distribution and species richness. In the tropical mountains, both tree height and species richness decrease steeply, and the tree height often stepwise. The decline of tree height and species diversity in the temperate mountains is far less pronounced except near the forest limit. Both trends are explained by their temperature regime.     

Bacterial genome mapper: A comparative bacterial genome mapping tool

Recently, next generation sequencing (NGS) technologies have led to a revolutionary increase in sequencing speed and costefficacy. Consequently, a vast number of contigs from many recently sequenced bacterial genomes remain to be accurately mapped and annotated, requiring the development of more convenient bioinformatics programs. In this paper, we present a newly developed web-based bioinformatics program, Bacterial Genome Mapper, which is suitable for mapping and annotating contigs that have been assembled from bacterial genome sequence raw data. By constructing a multiple alignment map between target contig sequences and two reference bacterial genome sequences, this program also provides very useful comparative genomics analysis of draft bacterial genomes. AVAILABILITY: The database is available for free at http://mbgm.kribb.re.kr.     

Vegetation composition,structure, and biomass of two unpolluted watersheds in the Cordillera de Piuchué, Chiloé Island,Chile

Research in pristine forests provides a necessary reference of energy and nutrient cycling in absence of anthropogenic influence. Therefore two unpolluted watersheds in the Cordillera de Piuchué of southern Chile (42 °30 S) were chosen for detailed ecosystem analysis. The goals of this study were to quantify the distribution of the living biomass in the research watershed and to document topographic gradients in the vegetation. Across a small spatial gradient from ravine bottom to ridgetop (approximately 60 m in elevation and < 300 m in length) in the Cordillera de Piuchué watersheds, there were significant shifts in vegetation composition, structure, and biomass. Based on sampling in 18, 100 m² plots, we identified three distinct community associations: a Fitzroya forest at the bottom of the watershed, a mid-slope Pilgerodendron-Tepualia transition zone, and a ridgetop moorland community. The Fitzroya forest was dominated by a cohort of approximately 400 year-old Fitzroya cupressoides trees. Both tree basal area (138 m²/ha) and total live biomass (656 Mg ha^–1) reached a maximum in this vegetation type. The Pilgerodendron-Tepualia forest consisted of smaller, shorter, and younger trees with dominance shared by Pilgerodendron uviferum, Tepualia stipularis, and to a lesser extent, F. cupressoides. Basal area and biomass were half that of the Fitzroya forest (69.5 m² ha^–1; 350 Mg ha^–1) but tree density was 65% greater. The moorland can best be described as an open community of mosses and cushion plants that included low stature individuals of P. uviferum, F. cupressoides, and T. stipularis. The size and age structure of F. cupressoides in the bottomland forest suggest that the current cohort of adult trees was established following a catastrophic disturbance and that F. cupressoides is unable to regenerate under its own canopy. In contrast, the size structure of the tree populations in the Pilgerodendron-Tepualia zone indicates that all the constituent tree species, except F. cupressoides, are able to reproduce at least at some microsites in the understory. The watershed-level means for live biomass were 306 Mg ha^–1 of aboveground tree biomass, 25 Mg ha^–1 of large root biomass (diameter ge 1 cm), and 46 Mg ha^–1 of small root biomass (diameter < 1 cm).     

陕南秦巴山区药用植物群落物种多样性研究

采用样方法对陕南秦巴山区药用植物群落物种多样性进行了研究。结果显示,该地区药用植物共计105科268属361种,其中药用裸子植物5科6属7种,药用被子植物92科254属344种,药用蕨类植物7科8属10种;含1属的科、含2~5属的科和含1种的属的药用植物数量较多,所占比例较高;该地区各植被类型的物种多样性变化各具特点,其中,物种丰富度指数(S)、Shannon-Wiener多样性指数(H)及Simpson多样性指数(D)表现为:乔木层最小、灌木层较大、草本层最大,但Pielou物种均匀度指数(J)的变化较为复杂;药用植物群落总的物种丰富度、乔木层物种丰富度和草本层物种丰富度均随海拔的升高表现出先升高后下降的趋势,且物种丰富度最大值出现在海拔1000~1200 m的山地常绿落叶阔叶林和温性针阔混交林的过渡区域,但灌木层物种丰富度与海拔之间无相关关系。本研究结果为阐明山地物种多样性的分布格局提供了基础资料,也为该区域药用植物的保护和管理提供参考。     

Mapping and characterization of mangrove plant communities in Hong Kong

Ecological surveys were carried out to investigate the distribution and characterization of remaining mangrove stands in Hong Kong. The field studies indicate that 43 mangrove stands, excluding Mai Po Nature Reserve, still remained along the coastline of Hong Kong despite tremendous reclamation and development which occurred in the past 40 years. Most mangrove stands were found in Deep Bay (western part)and Sai Kung District (eastern coasts). The total areas occupied by these mangrove stands were 178 ha,varying from a very small stand (with 1–2 mangrove shrubs) to fairly extensive mangroves in Deep Bay (> 10 ha). It appeared that mangrove stands located in Deep Bay area were larger than those in the eastern coasts. Twenty plant species were identified from these stands, with 13 being exclusive or associate mangrove species. The major constituent species were Kandelia candel, Aegiceras corniculatum, Excoecaria agallocha and Avicennia marina. Rare species such as Heritiera littoralis were only found in a few mangrove stands. Out of the 43remaining mangrove stands, 23 were more worthwhile for conservation and their plant community structures were further investigated by transect and quadrat analyses. The importance values (sum of relative abundance,frequency and dominance) show that K. candel was the most dominant species. Species richness and Simpson's indices together with tree height, tree density and canopy area fluctuated significantly between mangrove stands. These values were used to prioritize the conservation potential of the remaining mangrove stands in Hong Kong. This revised version was published online in August 2006 with corrections to the Cover Date.     

A comparison of major histocompatibility complex SNPs in Han Chinese residing in Taiwan and Caucasians

Summary Genetic dissection of complex diseases is both important and challenging. The human major histocompatibility complex is involved in many human diseases and genetic mechanisms. This highly polymorphic chromosome region has been extensively studied in Caucasians but not as well in Asians. Thus, we compared genotypic distributions, linkage disequilibria and haplotype blocks between Caucasian and Taiwan’s Han Chinese populations. Moreover, we investigated the population admixture and phylogenetic system in Han Chinese residing in Taiwan. The results show that Taiwan’s Han Chinese differ drastically in genotypic information compared with Caucasians but are relatively homogeneous among the three major ethnic subgroups, Minnan, Hakka and Mainlanders. Differences in allele frequency (AF) between Taiwanese and Caucasians in some disease-associated loci may reveal clues to differences in disease prevalence. The results of ethnic heterogeneity imply that public databases should be used with caution in cases where the study population(s) differs from the population characterized in the database. The high homogeneity we observed among the Taiwanese subpopulations mitigates the possibility of spurious association caused by ignoring population stratification in Taiwanese disease gene association studies. These results are useful for understanding our genetic background and designing future disease gene mapping studies.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Rate of succession in restored wetlands and the role of site context

Question: Are changes in plant species composition, functional group composition and rates of species turnover consistent among early successional wetlands, and what is the role of landscape context in determining the rate of succession? Location: Twenty‐four restored wetlands in Illinois, USA. Methods: We use 4 years of vegetation sampling data from each site to describe successional trends and rates of species turnover in wetlands. We quantify: (1) the rate at which composition changes from early‐successional to late‐successional species and functional groups, as indicated by site movement in ordination space over time, and (2) the rate of change in the colonization and local extinction of individual species. We correlate the pace of succession to site area, isolation and surrounding land cover. Results: Some commonalities in successional trends were evident among sites. Annual species were replaced by clonal perennials, and colonization rates declined over time. However, differences among sites outweighed site age in determining species composition, and the pace of succession was influenced by a site's landscape setting. Rates of species turnover were higher in smaller wetlands. In addition, wetlands in agricultural landscapes underwent succession more rapidly, as indicated by a rapid increase in dominance by late‐successional plants. Conclusions: Although the outcome of plant community succession in restored wetlands was somewhat predictable, species composition and the pace of succession varied among sites. The ability of restoration practitioners to accelerate succession through active manipulation may be contingent upon landscape context.