Rare Species and Ecosystem Functioning

Abstract:  The role of diversity in the maintenance of ecosystems has been studied widely in the past decade. By correlating richness and diversity with basic ecosystem processes, these investigations lend support to the hypothesis that species diversity significantly influences ecosystem functioning and, in turn, provide support for the conservation of biodiversity. Nonetheless, the majority of these investigations demonstrate that conservation of a relatively small number of generally dominant species is sufficient to maintain most processes. Indeed, there is remarkably little evidence to support the contention that less common species, those likely of highest conservation concern, are important in the maintenance of ecosystem functioning. Here we summarize studies, most employing alternative methodological strategies, wherein less common and rare species are demonstrated to make significant contributions to ecosystem functioning. Evidence exists among studies of keystone species, aggregate effects of less common species, and species turnover. Our findings suggest that (1) less common species can make significant ecosystem contributions; (2) further investigation into the effects of rare and less common species on ecosystem maintenance is sorely needed; (3) further investigation should embrace a variety of approaches; and (4) until further research is conducted a prudent conservation approach is warranted wherein the contribution of less common species to ecosystem functioning is assumed.     

黄河三角洲附近海域底栖动物多样性及其保护措施

在对黄河王角洲附近海域３０个站点底栖动物调查基础上，辅以文献资料法，综合分析了底栖动物物种多样性，研究了生物多样度以及与均度、单纯度之间的关系，并提出了保护底栖动物多样性的措施。结果表明：该海域共记录底栖动物２２２种，物种较为丰富；生物多样度为０～４．４２，均度为０～２．０１，单纯度为０．１１～１．００；多样度与均度呈显著的正相关，与单纯度呈显著的负相关。     

Conservation for the landscape ecological diversity in Wulingyuan scenic area of China

Wulingyuan is located at the mountainous area of the middle reach of the Yangtze River,it is one of the three nature heritages in China which ranks in the “List of Worls‘s Heritage”by UNESCO.It is characterized by quartz sandstone peaks landform with several landform components(pattern,corridor)and rich in landscape ecological diversity and biodiversity.The main patterns(ecosystem)include mid-height mountain peaks,rift-avlley and streams among peaks,peaks and gullies on slopes,square mountain-platforms and peaks among blind valleys and so on.The corridor system consists of natural corridors and artificial corridors among which the stream corridors account for a major part.The fracturing of habitat is unfavorable for the biodiversity conservation,but meanwhile the habitat diversity leads to an increase in biodiversity.Therefore,it is still rich in landscape ecological diversity in Wulingyuan.The biodiversity at the level of landscape component(ecosystem) and the function of the Wulingyuan complex ecosystem,and the measures for the biodiversity conservation in Wulingyuan ecotourism area are discussed in this paper.     

铁矿石港口对海域环境的影响——以宝钢马迹山铁矿石中转港口为例

通过对马迹山铁矿石中转港建港前后的海域水质、沉积物、浮游动植物及潮间带生物资源现状监测资料的回顾评价,分析了铁矿石港口营运对海域生态环境产生的影响。结果显示:铁矿石港口的运营对海洋生态环境有一定的影响,表现在潮间带生物量、底栖生物、港口前沿沉积物中油类含量的变化等。并分析了产生环境影响的原因,提出防止港口对海域环境影响的相应环保措施建议。     

京密运河与北京排污河浮游藻类的群落演替与水质污染的关系

对京密运河及北京排污河进行了不同季节的藻类生态调查,根据藻类群落结构特征,对河流质量进行评价,并将河流水质划分为五级.相关性分析结果表明,藻类数量和生物量与水质相关性显著.根据藻类组成、分布特征及河流水质选出了作为评价京密运河和北京排污河污染程度的几种指示藻类.     

Application of the quadratic entropy indices for diversity studies of drosophilid assemblages

Most diversity indices widely used in ecology (e.g. the Shannon-Wiener index and the Gini-Simpson index) do not reflect taxonomic or other differences among species. Quadratic entropy, proposed by C.R. Rao (1982), takes these differences into account. The aim of this paper is to demonstrate the application of this diversity index in investigations of drosophilid species diversity. Quadratic entropy and Simpson index values are also compared. The elements of the difference matrix in the quadratic form are taxonomic differences (distances) among the species. The difference is defined by the position of the lowest-ranking taxon containing both species. According to the results, the Gini-Simpson index and the taxonomic quadratic entropy are positively correlated. The observed differences are due to the fact that assemblages with greater taxonomic distances produce greater quadratic entropy. Drosophilid species can be assigned to specific life habit classes, more specifically to resource types. After postulating differences between the types, we used the quadratic entropy measure to analyse resource diversity. These kinds of examinations approximate to an operative association of species diversity and environmental diversity.     

Differing Effects of Cattle Grazing on Native and Alien Plants

Abstract:   Habitat managers use cattle grazing to reduce alien plant cover and promote native species in California grasslands and elsewhere in the western United States. We tested the effectiveness of grazing as a restoration method by examining the effects of herbivory on native and alien plants. At Carrizo Plain National Monument, California, we surveyed native and alien species cover in adjacent grazed and ungrazed areas. We also established experimental plots in which plants were clipped or mulch (dead biomass) was removed. In addition, we clipped plants grown in pots and plants in the field that grew with and without competitors. Native species were negatively affected by clipping in 1999, 2000, and 2001, whereas alien species were unaffected. In the experimental field plots, the European annual forb Erodium cicutarium compensated in growth and reproduction following simulated herbivory. In contrast, growth and reproduction of the native perennial bunchgrass Poa secunda were reduced 1 year after clipping. In pots, E. cicutarium overcompensated and grasses undercompensated. In the field, European grasses were unaffected by the removal of competitors. It is unclear by what mechanism E. cicutarium was able to compensate, but the ability may be related to its basal rosette growth form and indeterminately growing inflorescences. The native California grassland community assembled in the absence of grazing herds, whereas invasive European species have been exposed to grazing for centuries. It may be that these invaders have adaptations that better enable them to recover from grazing. In the grassland we studied, the strategy of livestock grazing for restoration is counterproductive. It harms native species and promotes alien plant growth.     

广西大明山自然保护区鱼类资源调查研究

~~广西大明山自然保护区鱼类资源调查研究@黄文$湖南省第一师范学校!湖南长沙410002 @邓学建$湖南师范大学生命科学学院动物系!湖南长沙410081~~~~~~     

Determination of Fish Community Composition in the Untempered Regions of a Thermal Effluent Canal – The Efficacy of a Fixed Underwater Videography System

High flows and deep waters associated with thermal dischargecanals invoke safety concerns and preclude the use of conventional fish sampling methodologies. Despite these challenges, it is critical that assessments of thermal effectsfrom power generation do not rely solely on data collected in the plume, but also focus on fish living in the canal, particularly in regions above the zone of tempering influence. We deployed a fixed underwater videography apparatus to monitor the community composition and abundance patterns of fish in the Nanticoke thermal generating discharge canal on the north shore of Lake Erie from February 1, 1999 until July 31, 1999. We also compared the number of species observed using video to angling surveys, visual observations through the air/water interface and two modified netting procedures. Our results indicate that videography permitted the detectionof the most species and the highest number of individuals. Variable visibility was the largest limitation of this approach. The addition of infrared lighting for low light conditions and a series of cameras positioned at several depths would be a cost effective, safe, and efficient method ofassessing community structure and behaviour of fish in thermal discharge canals.     

电厂增温对中小型浮游动物群落结构的影响

为探明电厂增温可能导致邻近海域浮游动物的小型化问题,对小网目（网目77μm）采集的象山港国华电厂排水口附近样品数据进行了分析.结果表明：本次调查共鉴定出75种浮游动物（包括浮游幼体、卵与仔鱼）,优势种18种,年平均丰度为27690.0ind/m³.该海域主要由中小型桡足类和浮游幼体组成,且个体体长以<1000μm中小型浮游动物占绝对优势.其中,体长<500μm小型浮游动物丰度在各月份和各断面均最高,平均丰度占总丰度比例>58.2%;体长500~1000μm占比>34.8%;而体长>1000μm所占比例仅为7%.经群落相似性分析（ANOSIM）,群落结构具显著的季节性差异（P<0.05）,但不同断面的空间结构无显著差异.群落相似性百分比（SIMPER）分析显示,导致群落结构时空差异的主要判别种有大同长腹剑水蚤（Oithona similis）、异体住囊虫（Oikopleura dioica）和砂壳虫（Difflugia sp.）等.电厂增温导致大型浮游动物（>2000μm）全部远离排水口0.2km断面（D02断面）,主要幼体类群的桡足类无节幼体和桡足幼体则在增温海域分布较均匀,几乎不受影响.而一些高丰度小型浮游动物,如砂壳虫、短角长腹剑水蚤（Oithona brevicornis）、伪长腹剑水蚤（Oithona fallax）大量聚集于排水口,使D02断面的浮游动物丰度最高,达35704.1ind/m³.多样性分析显示,海域增温与种类数（S）间的线性关系不显著（P>0.05）,而与Shannon指数（H'）、Pielou均匀度（J'）、Simpson指数（D'）间均存在显著的线性关系（P<0.01）.据回归方程斜率计算,每增温1℃会导致浮游动物H'、J'、D'和S分别降低5.4%、5.0%、3.8%和2.9%.