Diversity declines in Microstegium vimineum (Japanese stiltgrass) patches

The spread of invasive plant species and their impacts on plant communities have received international attention as global trade and global environmental change enhance the colonization and establishment of introduced species and threaten the integrity of native ecosystems. Because introduced species vary in their impact, studying the relationship between invasion and native communities is necessary to guide allocation of finite management resources. By studying adjacent pairs of invaded and uninvaded plots across an eastern United States forested landscape, we demonstrate Microstegium vimineum was associated with local declines in species richness and cover of native species. Negative impacts of M. vimineum on species richness did not emerge until August when M. vimineum cover and height were greatest, highlighting the value of following study subjects through the growing season. In contrast, native species cover was already lower in invaded plots early in the growing season. M. vimineum invasion was not the only important driver of species richness and community composition within the study region; abiotic environmental gradients, such as soil nitrate concentration and pH, across the six study sites were also important in affecting species richness and cover, but lessened in explanatory power through the growing season. We conclude that M. vimineum has effects on community structure that may have long-term consequences for biodiversity. Studies which track sites through time and consider multiple scales are required as invaders impact multiple biotic and abiotic factors operating at different spatial and temporal scales.     

从北京山区脱贫致富案例获得的几点启示

社会主义新农村建设是构建和谐社会的重要基础,新农村建设的首要问题是发展生产,发展生产的关键是产业的选择.此问题在资源丰富、相对贫困的广大山区表现更为突出.结合对北京山区的概况分析,通过对不同资源背景下不同发展模式的北京山区脱贫致富的几个案例的分析,可以得出创新是促进农村经济发展的强大动力,提高基层组织领导经济发展的能力是富民增收的重要基础等启示.     

不同园林植物类型昆虫群落的比较研究

对4种不同植物类型(百花园、园林植物苗圃、草坪、国槐行道树)组成的昆虫群落的特征指数进行分析比较。不同植物类型的昆虫群落的物种数、多样性、均匀性等均有不同程度的变化,植物种类丰富的百花园、苗圃和草坪,昆虫物种数远远多于植物种类单一的国槐行道树,其多样性指数、均匀性指数也较国槐昆虫群落高。     

Increased crop diversity reduces the functional space available for weeds

There is a drive to improve the sustainability of agricultural systems including the biodiversity component. Cultivar mixtures offer yield benefits from the same land area, but the mechanisms behind this overyielding have not been completely worked out. One potential mechanism is improved competition with weeds. We use an experimental approach of varying barley (Hordeum vulgare L.) genotypic and phenotypic diversity to test the hypothesis that increases in diversity have an impact on weed growth strategies and community assembly, or if responses are driven by barley performance. There was no effect of increasing barley mixture diversity on weed traits, either in terms of species means or the community-weighted mean. However, Functional Richness of the weed community decreased with increasing barley mixture diversity mainly as a result of reduced specific leaf area Functional Richness. This pattern was driven by a reduction in species richness of the weed community rather than by reduced variation within species. Whilst barley phenotype had different impacts on weed traits, there were no specific mixtures of phenotypes or genotypes that had consistent effects on community assembly or weed species responses. The competitive exclusion of weed species could have agronomic and environmental benefits, through better targeting or less frequent use of herbicides. Growing crop mixtures is one of many strategies available to improve agricultural sustainability and resilience, and one that has clear benefits.     

夏棉田昆虫群落结构的研究

[目的]为夏棉田害虫治理对策提供科学依据。[方法]采用5点取样法调查取样范围内地面和植株上所有昆虫、螨类等种类和数量,计算昆虫群落的丰富度、优势度指数、均匀度指数和多样性指数,研究该夏棉田昆虫群落的结构。[结果]夏棉田中昆虫群落组成较为丰富,由10目30科43种昆虫组成,丰富度最大值为22,害虫类和天敌类昆虫的相对丰富度分别为80.22%和19.78%。昆虫群落的多样性指数最大值为2.095 1,均匀度最大值为0.738 5,群落的优势集中性指数最大为0.954 4。夏棉田害虫优势种是棉蚜和烟粉虱;天敌优势种为棉蚜蚜茧蜂。[结论]该研究对棉花害虫的可持续治理有重要的指导意义。     

西双版纳望天树林十五年的动态变化研究

以5块西双版纳望天树林固定样地15年来连续观测的资料为基础,对乔木层1993、1998、2003、2007年等不同年份的株数、丰富度、物种多样性指数、生态优热度、均匀度和胸高断面积等变化进行研究。结果表明,望天树群落的株数以较小的幅度减少,这是因胸高断面积的不断增加而引起的自然稀疏过程;而株数、丰富度、均匀度、物种多样性指数以及胸高断面积的变化体现了望天树群落还处于缓慢发展之中,但是已经接近顶级群落的演替阶段。     

关帝山文峪河流域上游河岸林生物多样性垂直分布格局研究

笔者通过测算丰富度指数、均匀度指数和多样性指数,分析了关帝山文峪河流域上游河岸林不同群落类型的生物多样性垂直分布,得出3种指数随海拔的垂直变化皆有一致的表现,即生物多样性在中等海拔处达到最大,符合“中间膨胀”规律（mid-altitude bulge）,也就是在中度海拔处生物多样性最高,这是群落物种组成和人为干扰双重作用的结果.     

板栗树冠节肢动物群落季节动态研究

分别分析了群落总体及其亚群落数量季节动态以及群落结构特征的季节动态,共采集节肢动物136种,隶属于12个目、63个科。群落害虫优势类群为同翅目、鞘翅目和鳞翅目,天敌优势类群以蜘蛛目为主。节肢动物群落个体总数量两个高峰期分别出现在4月下旬和9月中旬,整个节肢动物群落的数量变化主要由同翅目特别是该目中蚜虫的数量变化而引起。害虫亚群落的个体数量变化左右了整个群落的数量变化,总群落的物种丰富度、多样性指数和均匀度指数与害虫亚群落的变化趋势较为一致。     

太原市公园植物群落稳定性研究

为考察城市公园植物群落稳定性与植被特征的相关性,筛选太原市15个有代表性的公园,设定筛选46个典型样方后,采用M-Godron稳定性测定方法,对所选样方进行稳定性研究。所得稳定性结果与太原市实际情况基本相符,表明所选择的稳定性计算方法可行。可以看出稳定性与群落物种丰富度关系较为密切,稳定性高的样方,其物种丰富度也较高,反之也成立。两者的变化趋势基本一致。而稳定性较高的样方内,灌木与乔木的比值接近6:1;稳定性差的样方内,灌木与乔木的比值则远离6:1。较稳定的19号(学府公园)与27号(太原森林公园),这两个样方内植物群落都具有乔、灌、草结构,物种丰富,各层植物种类多样,平面布局密度合理。较不稳定25号(西海子公园)和38号(玉泉山森林公园)样方,群落空间结构只有乔木和草本两层,缺乏灌木层,群落丰富度较差,乔灌比例严重失调,同时游人干扰多,养护频率低,群整体稳定性较低。总之,为确保城市公园绿地群落的稳定性,除了植物群落自身发展演变之外,还需要适度的、合理的人工管理养护。     

Biodiversity response to intensive biomass production from forest thinning in North American forests - A meta-analysis

Demand for alternative energy sources has led to increased interest in intensive biomass production. When applied across a broad spatial extent, intensive biomass production in forests, which support a large proportion of biodiversity, may alter species composition, nutrient cycling and subsequently biodiversity. Because forest thinning and fuels treatment thinning are viewed as possible wide-spread biomass harvest options, it is important to understand what is known about forest biodiversity response to these practices and what additional information is needed by forest managers and policymakers. Therefore, we summarized documented relationships between forest thinning treatments and forest biodiversity from 505 biodiversity effect sizes (incl. taxa and guild abundance and species richness measures) from 33 studies conducted across North America. We used meta-analysis to summarize biodiversity response by region, taxa and harvest treatments. Biodiversity responses included species richness, diversity, abundance of taxa or groups of species (guilds) and abundance of individual species for birds, mammals, reptiles, amphibians, and invertebrates. Forest thinning treatments had generally positive or neutral effects on diversity and abundance across all taxa, although thinning intensity and the type of thinning conducted may at least partially drive the magnitude of response. Our review highlights the need for more research to determine effects of thinning on amphibians and reptiles and manipulative experiments designed to test the effects of biomass removal on biodiversity.