Presence of cushion plants increases community diversity in the high equatorial Andes

Cushion plants are a common growth form in the equatorial páramo vegetation and their surfaces are often colonized by other plants. This paper analyzes the effect of the cushion plants on the community diversity at 4650 m on the eastern slope of the Iliniza volcano in Ecuador. Ninety sample plots of 1 m² size were located in the study area and were divided into 25 subplots in which presence and abundance of plant species was recorded. The community diversity was expressed as species richness, Simpson's diversity index, and evenness. Correlation between the cushion species and the composition of the colonists was measured with the CCA ordination analysis, correlation between the cushion cover and community diversity was measured by means of correlation analysis. Randomized species–area curves were used to compare richness of plant communities with and without the cushions. A total of 32 species were found including five cushion plants. Most species preferred to grow on the cushion surface whereas only a few species were able to colonize open ground. Species richness and Simpson's index were significantly correlated to the cushion area but no correlation was found for evenness. The cushions were usually composed of more than one species which hampered the examination of the cushion–colonist specific relationships. Nevertheless, cushions of Azorella and Arenaria seemed to provide more favorable habitat for colonization than the other cushion species. Comparison with an earlier study made on Iliniza indicates that the presence of the cushions significantly increases the richness of the plant community.     

Predicting diversity of juvenile neotropical fish communities: patch dynamics versus habitat state in floodplain creeks

The species richness of communities should largely depend on habitat variability and/or on habitat state. We evaluated the ability of habitat variability and habitat state to predict the diversity of juvenile neotropical fish communities in creeks of a river floodplain. The young-fish fauna consisted of 73 taxa, and samples were well distributed over a wide range of relevant temporal and spatial habitat variability. We were unable to demonstrate clear patterns of richness in relation to temporal and spatial habitat variability (if habitat state variables were not included), regardless of the temporal variability scale, the grouping of sites (up- and downstream sites differed in temporal variability patterns), taxonomic units or life stages considered. Using stepwise multiple regression, 36% of the variance in species richness was explained for all data, and at best 47% was explained for all taxonomic units at upstream sites using temporal and spatial habitat variability and habitat state (bank length, mean width, mean water level before fishing and/or water turbidity). Using Monte Carlo simulations, we blindly predicted 31% (all data) and at best 37% (all upstream taxa) of the observed variance in species richness from these model types. This limited precision is probably because rare species produced most of the richness patterns in our creeks. The prediction of these rare species is generally difficult for various reasons, and may be a problem in many ecosystem types. Received: 6 July 1998 / Accepted: 16 November 1998     

祁连山区不同海拔草地群落的物种多样性

依据植物在各海拔带出现的频率和不同海拔带植物种的生活型,对祁连山区草地群落海拔2500～3000m的物种α多样性变化特征进行了研究．结果表明,随海拔升高,Shahnon-Wiener指数从1．432上升到1．832,Simpson指数的变化较为复杂．海拔2701～2800m带是物种多样性的一个重要转折点,是物种多样性较丰富的地带．在祁连山草地群落中,有毒的与食性较差的物种在各海拔带所占比例均超过50％,生物量占到整个样地生物量的60％以上,物种多样性已呈现衰退．     

乌伦古河流域克孜赛水库浮游植物群落组成

克孜赛水库是乌伦古河源头的一个小型水库,2008年7月(夏季平水期)、2008年10月(秋季枯水期)和2009年5月(春季丰水期)对水库内浮游植物群落进行了调查分析,共鉴定出浮游植物102种(属),隶属于8个门,以硅藻门和绿藻门为主。3个时期浮游植物密度变化趋势为:枯水期(25.221±3.605×106ind/L)>平水期(12.539±1.064×106ind/L)>丰水期(1.052±0.077×106ind/L)。各季节优势种的组成因气候温度差异而变化,其中以夏季平水期最多,达9种。克孜赛水库温度和水量的变化共同导致了水库浮游植物种类组成、密度、优势种和生物多样性指数的季节变化。Shannon-Weaver多样性指数(H)和Pielou均匀度指数(J)变化趋势较一致:平水期>枯水期>丰水期,而Margalef丰富度指数(D)则于丰水期达最大值。     

Geographic patterns and environmental correlates of taxonomic and phylogenetic diversity of aquatic plants in China

Studies on large-scale geographic patterns of aquatic plant diversity can promote research on the generality of macroecological patterns in different ecosystems. Here, we compiled a checklist of 889 aquatic angiosperms in China, including 738 helophytes (emergent and marshy plants) and 151 hydrophytes (submerged, free-floating, and floating-leaved plants). We explore the geographic patterns and environmental correlates of aquatic plant diversity based on six metrics including species richness (SR), weighted endemism (WE), phylogenetic diversity (PD), phylogenetic endemism (PE), the standardized effect size of phylogenetic diversity (PDses), and the standardized effect size of mean phylogenetic distance (MPDses). Our results show that the diversity of aquatic plants in China is extremely uneven, with high diversity in southeastern China and low diversity in northwestern China, and the geographic patterns of taxonomic and PD are generally consistent. The pattern of helophytes differs from that of hydrophytes. Notably, the wavy-shaped pattern of aquatic plant diversity (especially SR and PD for hydrophytes) across the latitude observed in this study is not consistent with those previously observed for aquatic plants in other continents. Climatic variables and water environmental variables are the main drivers of aquatic plant diversity in China; however, the effects of individual variables differ between helophytes and hydrophytes. Water environmental variables have a greater impact on PDses and MPDses of hydrophytes than those of helophytes. Overall, our work provides insight into understanding the large-scale patterns of aquatic plant diversity and is a critical addition to previous studies on the macroecological pattern of terrestrial organisms.     

Patterns of bryophyte diversity and rarity at a regional scale

Information on bryophyte diversity and rarity were combined withinformation on soil conditions and land use for Walloon Brabant (centralBelgium, 1091 km²) in order to investigate whichlandscape features sustain the most rare and diverse species assemblages.Presence–absence of 325 bryophyte species was recorded in 87 grid-squaresof 4 × 4 km. Species diversity was significantly correlatedwith forest cover (r = 0.71, P <0.001), sandy soils (r = 0.61, P <0.001), loamy soils, (r = –0.68,P < 0.001), and agricultural fields(r = –0.49, P < 0.001). Themost diverse grid-squares possessed up to 182 species and were characterized byat least 10% forest cover and the presence of unique micro-habitats.Grid-squares with forest cover reaching at least 10% but lacking uniquemicro-habitats contained between 90 and 130 species. Below 10% forest cover,diversity ranged between 55 and 110 species per grid-square. However, even theleast diverse cultivated areas included a significant amount of the regionallyrare species. A number of the latter are characteristic in other areas forspecific primary habitats lacking in Walloon Brabant but display an unexpectedability to disperse throughout hostile areas and colonize secondary habitats.The tendency of such species to occur in man-made habitats decreased our abilityto predict species richness and rarity from landscape features and soilconditions.     

西凉湖水生植物多样性研究

研究了江汉湖群西凉湖水生植物多样性的现状及其变化 ,讨论了西凉湖水生植物多样性丧失的原因和保护的途径。主要结果是 :( 1 )西凉湖现有水生植物 3 2科 5 6属 77种 ,优势种类为微齿眼子菜、密齿苦草、轮叶黑藻、菹草、野菱、双角菱、金鱼藻、凤眼莲和菰等。 ( 2 )西凉湖现有水生植物群落类型 1 3个 ,全湖水生植被覆盖率约为 61 %,平均生物量为 1 4 70 .5 g/m2 。 ( 3 )物种多样性指数最高的群落是“凤眼莲 +野菱 +双角菱群丛”(D =0 .8499,H =2 .975 8) ,其次为“菰—凤眼莲群丛”与“野菱 +双角菱群丛”(D =0 .840 1 ,H =2 .82 35 ;D =0 .83 2 4,H =2 .888) ,以微齿眼子菜群丛的多样性指数最低 (D =0 .2 2 81 ,H =0 .782 3 )。 ( 4 )二十年来 ,西凉湖水生植物多样性严重丧失 :植被覆盖率和全湖平均单位面积生物量分别下降了 3 8.80 %与 77.87%,先后有 8种水生植物 (水葱、荸荠、莲子草、乌菱、细果野菱、萍蓬草、睡莲、小眼子菜 )和 4个水生植物群落类型(荇菜群落、乌菱群落、马来眼子菜群落、穗花狐尾藻群落 )从西凉湖消失。 ( 5 )多样性丧失的原因是围网养殖、过度收获水草、耙捞蚌类螺类等人为干扰     

Plant species diversity is correlated with climatic factors differently at the community and the functional group levels: A case study of desert steppe in Inner Mongolia,China

In the desert steppe of Inner Mongolia, mean annual precipitation was found to be the dominant factor that correlated positively with species richness at the community level and for the perennial forb functional group. Shrub and semi-shrub functional group exhibited positive correlation with mean temperature of the coldest month.     

Laboratory conditions can change the complexity and composition of the natural aquatic mycobiome on Alnus glutinosa leaf litter

Community structure is of major interest when aquatic fungi are studied, particularly in leaf decomposition experiments. Although such studies are often conducted as laboratory experiments with microbial communities taken from the field, it remains unclear to what extent natural fungal communities can be sustained under experimental conditions. Here, we used DNA metabarcoding to investigate the development of fungal communities on alder leaves both under laboratory and field conditions. Five leaf conditioning treatments were compared by colonizing leaves in a stream, exposing stream colonized leaves to a defined medium or filtered stream water and using stream colonized leaves to inoculate sterile leaves in the defined medium or stream water. Fewer species were found on leaves that were inoculated under laboratory conditions, whereas differences in fungal community composition were comparably low in the other treatments, irrespective of the chosen medium. Possible shifts in fungal communities should therefore be considered in laboratory experiments.     

竹叶眼子菜种群遗传多样性与群落物种多样性关系的研究

以洪湖中的沉水植物群落及其优势种竹叶眼子菜(Potamogeton wrightii Morong)为研究对象,利用AFLP分子标记结合野外调查的方法,分析保护区(干扰较小)与非保护区(干扰较大,敞水区)中沉水植物群落的物种多样性与竹叶眼子菜遗传多样性之间的相关性。结果显示:洪湖沉水植物群落物种丰富度(S)和物种多样性辛普森指数(D)在保护区和非保护区均未发现显著性差异;竹叶眼子菜的重要值(IV)在保护区(5.2%~23.2%)较非保护区(8.5%~73.3%)稳定。竹叶眼子菜的遗传多样性在两个区未发现显著差异,其遗传多样性与群落物种多样性这两个指标在保护区、非保护区及全湖水平均不相关,说明沉水植物群落的物种多样性和竹叶眼子菜的遗传多样性对不同环境干扰的响应有所差异。     

A test of traditional diversity measures and taxonomic distinctness indices on benthic diatoms of soda pans in the Carpathian basin

Saline lakes are threatened all over the world and their conservation has been a key issue. Various diversity indices are available for ecological status assessments, however, with poorly explored relevance and applicability in saline, alkaline pans. Therefore, traditional diversity measures (species richness and Shannon diversity) and taxonomic distinctness indices (Average [AvTD] and Variance of Taxonomic Distinctness [VarTD]) were tested in more than 100 sampling sites of 39 soda pans in Central-Europe to find sufficient indicators of the ecological condition and simultaneously to facilitate their preservation according to the modern conservation practices. Results of the analyses showed that healthy soda pan ecosystems with high level of natural stress and reduced habitat heterogeneity are characterized by low diversity diatom assemblages. In soda pans where the stress can be extremely high from natural reasons, oligopoly of closely related species can develop: the average taxonomic distinctness appeared between genus and family level. The non-DNA-sequence based phylogenetic diversity measures (AvTD and VarTD), were generally sensitive to the trophic state of the lakes, in contrast to traditional diversity metrics, which were unequivocally indicative for the special physical and chemical parameters (e.g. conductivity, pH) of the soda pans. In some cases, when the response of the diversity measures for a given environmental variable (pH, temperature) overlapped, the AvTD was found to be a more precise indicator of the environmental changes (pH) than traditional ones. The decreasing tendency of the AvTD along the intensified natural impact may be explained by the long available time for the species to adapt to these special environments.     

植物群落功能多样性计算方法

以性状为基础的功能多样性指数在预测生态系统功能中起到越来越重要的作用.本文对近年来陆续出现的植物群落功能多样性指数进行综述.依据物种多样性指数的组成,功能多样性指数分为功能丰富度、功能均匀度和功能离散度指数.介绍了这3类指数的计算方法,有助于更好、更准确地理解“生物多样性-环境-生态系统功能”的关系.     

Insights into plant biodiversity conservation in large river valleys in China: A spatial analysis of species and phylogenetic diversity

Large river valleys (LRVs) are heterogeneous in habitat and rich in biodiversity, but they are largely overlooked in policies that prioritize conservation. Here, we aimed to identify plant diversity hotspots along LRVs based on species richness and spatial phylogenetics, evaluate current conservation effectiveness, determine gaps in the conservation networks, and offer suggestions for prioritizing conservation. We divided the study region into 50 km × 50 km grid cells and determined the distribution patterns of seed plants by studying 124,927 occurrence points belonging to 14,481 species, using different algorithms. We generated phylogenies for the plants using the “V. PhyloMaker” R package, determined spatial phylogenetics, and conducted correlation analyses between different distribution patterns and spatial phylogenetics. We evaluated the effectiveness of current conservation practices and discovered gaps of hotspots within the conservation networks. In the process, we identified 36 grid cells as hotspots (covering 10% of the total area) that contained 83.4% of the species. Fifty‐eight percent of the hotspot area falls under the protection of national nature reserves (NNRs) and 83% falls under national and provincial nature reserves (NRs), with 42% of the area identified as conservation gaps of NNRs and 17% of the area as gaps of NRs. The hotspots contained high proportions of endemic and threatened species, as did conservation gaps. Therefore, it is necessary to optimize the layout of current conservation networks, establish micro‐nature reserves, conduct targeted conservation priority planning focused on specific plant groups, and promote conservation awareness. Our results show that the conservation of three hotspots in Southwest China, in particular, is likely to positively affect the protection of biodiversity in the LRVs, especially with the participation of the neighboring countries, India, Myanmar, and Laos.     

Impact of resource availability on species composition and diversity in freshwater nematodes

This study investigates the long-term effects of resource availability in a freshwater nematode community. We carried out a mesocosm experiment where natural nematode communities were exposed to nutrient addition/depletion over 2 years. Compared to the nutrient-addition treatment, species richness and diversity were strongly reduced upon nutrient depletion. The functional group of bacterial feeders particularly suffered severely from nutrient depletion. The decrease in diversity of bacterial feeders was linked to reduced species richness and diversity of large omnivorous species, as predicted by trophic-dynamic models. Tilmans (1976) statement, that under low nutrient levels the best competitor dominates the system, was applicable in our system. Upon nutrient depletion, resource depletion led to a monoculture of 1 small bacterial feeder, but even after 2 years of resource depletion, up to 16 species still coexisted. Our results provide strong evidence that freshwater nematode systems can be regulated by nutrient competition.     

洮河国家湿地公园主要植物群落多样性对土壤环境因子的响应

内陆河湿地原生植被群落多样性对土壤环境因子的响应分析,有助于深入理解河岸带原生植物群落的生态适应策略。采用双向指示种分析（two-way indicator species analysis,TWINSPAN）和典范对应分析（canonical correspondence analysis,CCA）方法对研究区27个样方的原生植物群落进行分析,研究河岸带植物群落多样性与土壤因子之间的关系。结果表明：研究区主要原生植物有8种生活型,群落类型可分为女贞（Ligustrum lucidum）+野蔷薇（Rosa multiflora）群落、杠柳（Periploca sepium）群落、艾蒿（Artemisia argyi）+狗娃花（Heteropappus hispidus）群落、旋覆花（Inula japonica）+败酱（Patrinia scabiosaefolia）群落、沙棘（Hippophae rhamnoides）+小檗（Berberis thunbergii）群落和沙棘+红花岩黄耆（Hedysarum multijugum）群落6类。群落的Shannon-Wiener多样性指数（H''）整体呈下降趋势,Pielou均匀度指数（J）呈现增减交替的趋势,Simpson优势度指数（C）整体呈增加趋势,土壤粉粒含量与Simpson优势度指数（C）呈显著正相关关系（P<0.05）,其他土壤因子与多样性指数无显著相关关系（P>0.05）,表明土壤中粉粒含量是影响河流湿地原生植物群落分布和多样性的关键因子之一。内陆河流湿地土壤质地类型的差异性一定程度上决定河岸带湿地生态系统原生植物群落的种类组成和分布格局。     

永定河干涸段(卢梁段)河流廊道植物群落数量分类及多样性特征

为探究永定河干涸段河流廊道的植物群落结构特征及多样性特征,给永定河河道防护林、水源涵养林建设等提供科学的理论依据,通过对河流廊道植物群落的实地调查,对124个植物群落进行了TWINSPAN数量分类,并探究了不同层次间的物种多样性的区别以及垂直和水平梯度上的分布格局。结果表明:(1)植物群落包括9种群丛类型,其中优势群丛为"狗尾草+猪毛菜+尖头叶藜群丛"、"狗尾草群丛"和"加杨-狗尾草+蒺藜群丛"。(2)草本层物种的丰富程度和均匀程度整体大于乔木层,且物种组成复杂程度的变化幅度更大。(3)从垂直梯度上看,植物群落乔木层上游的物种结构组成较下游更加丰富、整体分布更加均匀,草本层从上游到下游物种组成的丰富程度和均匀程度先降低后升高、再降低;从水平梯度上看,越靠近左、右两堤,乔木层的物种结构组成越丰富、分布越均匀,左堤的物种组成较右堤更加复杂且分布更加均匀,草本层的物种多样性在水平梯度上变化较大,在靠近左堤的位置物种组成最丰富。影响乔木层物种多样性变化的主要原因是人类活动干扰的强度。     

Functional diversity (FD), species richness and community composition

Functional diversity is an important component of biodiversity, yet in comparison to taxonomic diversity, methods of quantifying functional diversity are less well developed. Here, we propose a means for quantifying functional diversity that may be particularly useful for determining how functional diversity is related to ecosystem functioning. This measure of functional diversity “FD” is defined as the total branch length of a functional dendrogram. Various characteristics of FD make it preferable to other measures of functional diversity, such as the number of functional groups in a community. Simulating species' trait values illustrates how the relative importance of richness and composition for FD depends on the effective dimensionality of the trait space in which species separate. Fewer dimensions increase the importance of community composition and functional redundancy. More dimensions increase the importance of species richness and decreases functional redundancy. Clumping of species in trait space increases the relative importance of community composition. Five natural communities show remarkably similar relationships between FD and species richness.