物种丰富度对集群生物量的影响及抽样、互补效应的检验

通过8种甲藻构建不同物种丰富度梯度的集群进行室内一次性培养实验,探讨了集群生物量随物种丰富度的增长模式,运用多因素方差分析检验集群内是否存在抽样效应. 运用超产分析、相对产量之和分析和子集分析方法,检验了集群内的生态位互补效应,并运用分离加性方程法定量分离了抽样与互补效应.结果表明: 集群生物量随物种丰富度呈饱和型上升趋势;集群内存在较强的互补效应;在指数生长期,某些特定物种对集群生物量有显著影响,但在生长稳定期,集群生物量不受个别物种出现与否的影响;在生长稳定期,抽样效应总体上为负,而互补效应与净生物多样性效应则总体为正.     

生产力、可靠度与物种多样性:微宇宙实验研究

近年来,生物多样性与生态系统功能的关系成为生态领域内一个重大科学问题。有一些实验研究表明,物种多样性的降低会使生态系统的生产力、稳定性等功能受损,然而对这些实验结果的解释却产生了激烈的争论,因为有两种机制-“生态位互补”和“抽样效应”都可能会产生这种结果。本项研究通过微宇宙实验探讨了物种多样性与生态系统生产力及其可靠度的关系。在10种单细胞藻类中随机抽取物种,构建具有不同物种丰富度的水生群落,并使同一物种丰富度水平的群落之间没有物种交叉,然后检测物种丰富度对群落生产力及其可靠度的作用,群落生产力以藻类干重表示,自实验开始后第4周起,每周测定1次,共测5次。结果显示：物种丰富度对群落生产力有正效应,并且这种正效应随时间推移而增强;许多混合群落的生产力超过了该群落内所有物种的单产,即发生了超产现象,在实验初期某些特定物种对一些混合群落生产力有主要贡献,而在实验后期却没有任何多物种群落的生产力受个别物种存在与否的影响,群落生产力的可靠度与物种丰富度之间不存在显著相关。从以上结果可以得知：物种多样性对群落生产力有着逐渐增强的正效应;物种多样性对生产力的正效应是生态位互补和抽样效应共同作用的结果,但随时间推移,抽取效应逐渐减弱,本顶研究支持了关于生态位互补与抽样效应在多样性正效应中共同起作用的认识,并说明了这两种机制的相对重要性随时间推移而发生改变。     

放牧干扰下高寒草甸物种、生活型和功能群多样性与生物量的关系

为明晰放牧强度对高寒草甸物种、生活型以及功能群多样性和生物量的时间累积作用以及对多样性与生物量之间相互关系的影响。选择青藏高原东北缘高寒草甸,在6个放牧强度样地连续4 a(2012—2015)进行物种、生活型、功能群多样性和生物量调查。采用重复测量方差分析和线性回归法分析放牧强度和放牧年份对物种、生活型、功能群多样性以及多样性与生物量之间的相关关系的影响。结果表明:(1)放牧强度和放牧年份均对生物量产生显著影响。随放牧强度增加,生物量显著降低。但随放牧年份延长,不同放牧强度区生物量无一致的变化规律。(2)放牧年份对物种、生活型和功能群丰富度、均匀度和优势度的影响均达到显著水平。但放牧强度和放牧年份只对物种丰富度产生交互作用,放牧强度对物种丰富度的影响具有时间的累积效应。(3)放牧干扰下不同层次多样性,仅物种丰富度与所有多样性指数显著相关,物种丰富度可以作为物种多样性测度的代表性指标。(4)多样性与生物量关系的研究,对丰富度而言,仅低放牧强度样地(Plot2)中物种丰富度随生物量增加而显著降低,其余放牧强度样地的物种、生活型和功能群丰富度均与生物量无关。对均匀度而言,高放牧强度样地(Plot4、Plot5、Plot6)生活型均匀度随生物量的增加而显著降低。对优势度而言,高放牧强度样地生活型优势度随生物量的增加而显著增加。生活型多样性可作为放牧干扰下生物量变化快速预测的有效指标。     

内蒙古典型草原建群种羊草基因型多样性抑制群落物种多样性的生态功能

植物群落的物种多样性以及群落建群种的基因型多样性对群落生态功能是否存在交互影响已成为群落生态学研究的热点内容。以内蒙古典型草原群落内常见物种为研究对象,研究了群落物种多样性与建群种羊草(Leymus chinensis)基因型多样性及其交互作用对群落生物量生态功能特性的影响。结果表明:(1)羊草基因型多样性、物种多样性及其交互作用对群落地上、地下和总生物量无显著影响(P0.05);(2)羊草基因型多样性、物种多样性及其交互作用对多样性效应(净多样性效应、互补效应和选择效应)有显著影响(P0.05)。羊草基因型多样性抑制多样性净效应的发挥,且主要抑制互补效应;而物种多样性则促进多样性净效应的发挥,主要表现为选择效应对地上生物量的正效应;(3)互补效应对群落生物量多样性净效应起主要贡献。实验所得结果不仅为探讨多样性效应在物种水平以及群落水平上对群落生物量的影响因素提供了重要启示,而且为内蒙古草原种质资源的保护及合理利用,乃至生态系统的恢复和重建提供理论指导。     

西江下游浮游植物群落周年变化模式

西江肇庆段是珠江干流汇入珠三角河网水域的咽喉通道,对2009年该江段的浮游植物群落组成及变化进行系统阐析.调查期间共发现浮游植物7门,245种(包括变种、变型),其中硅藻和绿藻是浮游植物群落组成的最主要类群,分别占总种数的42.44％和34.69％,其次是裸藻和蓝藻.PCA分析结果显示,浮游植物各类群的种类丰富度和生物量的周年变化趋势主要受水温和径流量的影响.浮游植物种类丰富度的周年变化呈现明显的高温季节高,低温季节低的特征,除因大多数藻类物种直接喜好高温之外,径流量的增大有助于真浮游绿藻种类的外源注入及半浮游和偶然性浮游硅藻种类的增加.浮游植物生物量的周年变化呈现明显的双峰型,峰值分别出现在8月和11月.然而8月份第1个高峰出现之前,生物量波动不大,尽管水温的升高有助于生物量的增加,但是径流量增大所带来的稀释作用掩盖了水温上升对浮游植物生长的促进作用.真浮游植物生物量的变化趋势和数值与总浮游植物极其接近,主要得益于真浮游硅藻物种颗粒直链藻在总种群中的绝对优势地位.综上,水温升高对浮游植物种类丰富度和生物量的增长均有促进,径流量的增大虽然有助于种类丰富度的增加,但不利于生物量的增加.     

浙江定海次生林内物种丰富度与生物量和生产力关系的环境依赖性

迄今生物多样性与生态系统功能关系的研究主要在物种组成随机配置的人工生态系统中进行, 在自然生态系统中研究较少, 且未考虑环境因子如何影响生态系统功能及其与生物多样性的关系。本研究选取亚热带广泛分布的次生林为研究对象, 利用模型拟合的方法, 探讨亚热带次生林中物种丰富度与生物量和生产力之间的关系, 以及环境因子(海拔、坡度、坡向、土层厚度)和次生林恢复时间(林龄)对生物量、生产力、物种丰富度与生物量和生产力间关系的影响。结果表明, 当不考虑环境因子时, 物种丰富度与生物量之间存在显著的线性正相关关系, 而与生产力之间存在显著的二次关系(先增加后减少的驼峰型)。当考虑环境因子时, 个体密度和土层厚度对生物量具有显著影响, 而环境因子对生产力并无显著效应。在坡度较陡、坡向朝南及土层较厚的环境条件下, 物种丰富度与生物量具有显著的线性正相关关系; 而在坡度较缓、坡向朝北及土层较薄的环境条件下, 物种丰富度不影响生物量。在较高海拔环境条件下, 生产力随物种丰富度先增加后减少(驼峰形状), 而在其他环境条件下, 生产力均不响应物种丰富度。以上结果说明自然森林生态系统中物种丰富度与生物量和生产力的关系存在差异, 且其相互间的关系依赖于环境因子。     

羊草基因型多样性能增强种群对干扰的响应

研究了不同基因型多样性(1、3、6三种基因型组合)羊草种群的地上生物量、地下生物量、分蘖数、根茎芽数和根冠比5个指标对干扰强度(用不同留茬高度来模拟)的响应。结果表明:(1)基因型多样性和干扰强度对地上生物量、地下生物量、分蘖数和根茎芽数均有显著影响(P0.05),但两者的交互作用不显著(P0.05)。其中,多基因型组合(3、6基因型组合)羊草种群中这4个响应变量的值均显著高于单基因型羊草种群(P0.05);而干扰强度的增加显著降低了这4个响应变量的值(P0.05)。对于根冠比这一响应变量来说,仅干扰强度对其产生了显著地影响(P0.05)。(2)29个基因型多样性效应值中,有25个值大于0,其中12个表现为显著的基因型多样性正效应。依Loreau和Hector的方法将多样性净效应分解后发现,互补效应和选择效应共同主导12个响应指标的基因型多样性效应,而互补效应独自主导3个、选择效应独自主导5个响应指标的基因多样性效应;但对基因型多样性正效应起主要贡献的是互补效应。所得结果表明,基因型多样性能提高羊草种群的表现,能增强羊草种群对干扰的响应,不同基因型间的互补作用对这种正效应起主要贡献,这将为该物种种质资源保护和合理利用提供理论指导。     

模拟人工湿地中的植物多样性与系统抵抗力

设计模拟人工湿地实验,探究铵干扰下生态系统抵抗力与物种多样性的关系。在90个沙培微宇宙中配置了4个物种丰富度梯度(1、2、3、4),设置了加铵干扰和无干扰2组处理。结果表明:(1)无干扰时植物地上生物量随物种丰富度的增加显著增加,而铵干扰会消解丰富度的正效应;(2)地上生物量对铵干扰的抵抗力与丰富度呈负相关;(3)抵抗力与未干扰的地上生物量负相关;(4)菖蒲(Acorus calamus)在系统中的存在会显著降低系统对铵的抵抗力,其他种无影响。本研究设置了新的干扰类型,拓展了多样性-抵抗力研究。     

青藏高原东缘人工草地群落物种丰富度对杂草入侵的影响

物种丰富度和生态系统功能间的关系是近年来生物多样性研究的中心问题,其中群落抗杂草入侵是其功能的重要表现形式。本文利用青藏高原东缘地区3种野生优良牧草：垂穗披碱草(Elymus nutans)、中华羊茅(Festuca sinensis)和羊茅(F. ovina),构建人工草地群落,探讨了物种丰富度与杂草入侵能力间的相互关系及其潜在的作用机理。结果表明：随着群落中物种丰富度的增加,入侵杂草的物种数、秧苗数和生物量均表现为显著下降趋势(P＜0.05);杂草的物种数、秧苗数和生物量间存在极显著的正相关(P＜0.01);群落的物种丰富度与入侵杂草间的负相关关系可能是选择效应和补偿效应共同作用的结果;2004—2007年,群落中入侵杂草的物种数和生物量有增加趋势,而秧苗数的变化趋势不明显。     

黄土高原典型草原群落结构和土壤水分对划破的响应

划破是草原改良的基础措施之一,划破强度是划破措施的关键环节,划破对草原健康持续管理有重要意义。目前的研究主要集中在划破对植物群落结构和生产力的影响上,然而草原植物群落与土壤水分对划破强度的响应尚不清楚。在黄土高原典型草原开展不同程度的草地划破试验,探究不同划破强度（27.4%、46.3%和61.9%）对草地植物群落物种多样性、生物量和土壤水分的影响。结果表明：3个划破强度下划破带物种丰富度显著低于未划破带1-3种/m²,划破带和未划破带群落相似性分别低于整区23.85%-119.23%和44.43%-84.55%。地上生物量随物种丰富度的增加而增大,且地上生物量与Simpson指数和Shannon Weiner指数显著负相关。3个划破强度下未划破带地下生物量和总生物量分别高于划破带88.2%-134.6%、52.4%-67.8%、2.5%-16.6%和103.9%-152.9%、59.3%-75.8%、9.1%-22.6%。植物群落物种丰富度和地上生物量随划破强度的增加呈"驼峰"型曲线变化,当划破强度分别为43.7%-55.3%和43.8%-45.7%时,植物群落物种丰富度和生物量均最高。本试验阐明了划破对典型草原植物群落特征和土壤水分的作用机制,研究结果为采用划破措施实现草地培育和草原修复提供了科学依据,对保护草地生物多样性和提高生产力具有重要意义。     

Trade-off between number and length of remote videos for rapid assessments of reef fish assemblages

Remote underwater videos are widely employed to assess the structure and composition of reef fish assemblages but the sampling effort employed on each survey differs considerably, indicating that both the number of assessments and video length could be optimized. We searched for this optimal sampling effort in remote video samples to conduct rapid assessments of community composition and discussed the relation between number of replicates and video length, and how it impacts the method's efficiency to characterize species assemblages. Remote video recordings from tropical reefs in northeastern Brazil were used to investigate how fish species richness and composition builds across time and number of assays. Videos as short as 5 min successfully recorded species richness, requiring about five repetitions to record most species that compose 80% of the total biomass. Recording species composition required even less time in these reefs, setting a minimum of 3 min with the same five videos. By comparing the detected richness per analysed time unit, we found several shorter videos recorded for more species than a few longer videos, indicating that increasing the sampling coverage in the reef area might be better than just extending the video length for rapid assessments.     

Beetle assemblages in ponds: effects of habitat and site age

• 1 Water beetle assemblages were sampled in each of 18 freshwater ponds, including 11 recently constructed sites designed to provide mitigation for wetlands destruction elsewhere, and seven older reference sites. There were three objectives: (a) to relate taxon richness and biomass of the beetles to the same properties of the wider aquatic invertebrate community, (b) to evaluate changes in beetle assemblage structure over time, and (c) to determine habitat effects on taxonomic composition, mean body size and trophic guild structure of the beetle assemblage.
• 2 Forty‐seven beetle genera were identified, representing 77 species. The beetles represented an average of 21.5% of total generic richness, but only 3.7% of total wet biomass of the wider invertebrate community.
• 3 Of all variables evaluated using canonical correspondence analysis (CCA), site age had the greatest influence on the beetle assemblage. Predatory dytiscids were early colonists at younger sites, while herbivorous curculionids and chrysomelids associated with particular types of vegetation typically occurred in older ponds. Mitigation ponds and reference ponds supported similar numbers of species. Reference sites, however, harboured substantially more unique species found at only a single site within the study area.
• 4 The presence of fish was also strongly related to beetle assemblage structure. Ponds with few or no fish contained about 3‐fold higher biomass and 3‐fold greater mean wet weight per individual compared to ponds with substantial fish assemblages.
• 5 Beetle assemblage composition varied among sites and sampling years, but beetle biomass, richness and species composition may be useful tools in evaluating the success of wetland mitigation efforts.

     

No correlation between the diversity and productivity of assemblages: evidence from the phytophage and predator assemblages in various cotton agroecosystems

Biodiversity research has shown that primary productivity increases with plant species number, especially in many experimental grassland systems. Here, we assessed the correlation between productivity and diversity of phytophages and natural enemy assemblages associated with planting date and intercropping in four cotton agroecosystems. Twenty-one pairs of data were used to determine Pearson correlations between species richness, total number of individuals, diversity indices and productivity for each assemblage every five days from 5 June to 15 September 2012. At the same trophic level, the productivity exhibited a significant positive correlation with species richness of the phytophage or predator assemblage. A significant correlation was found between productivity and total number of individuals in most cotton fields. However, no significant correlations were observed between productivity and diversity indices (including indices of energy flow diversity and numerical diversity) in most cotton fields for either the phytophage or the predator assemblages. Species richness of phytophage assemblage and total individual numbers were significantly correlated with primary productivity. Also, species richness of natural enemy assemblage and total number of individuals correlated with phytophage assemblage productivity. A negative but not significant correlation occurred between the indices of numerical diversity and energy flow diversity and lower trophic-level productivity in the cotton-phytophage and phytophage-predator assemblages for most intercropped cotton agroecosystems. Our results clearly showed that there were no correlations between diversity indices and productivity within the same or lower trophic levels within the phytophage and predator assemblages in cotton agroecosystems, and inter-cropped cotton fields had a stronger ability to support the natural enemy assemblage and potentially to reduce phytophages.     

Macrobenthos of a tidal impoundment at the Mai Po Marshes Nature Reserve,Hong Kong

The composition and spatial distribution patterns of the macrobenthic faunal assemblages of an 8-ha tidal impoundment operated as a traditional shrimp pond at the Mai Po Marshes Nature Reserve, Hong Kong, were studied in relation to temporal changes in local environmental conditions. Species richness, abundance and biomass of macrobenthos across 5 different sub-habitats (seaward, middle, and landward parts of open water unvegetated areas, and Phragmites- and Kandelia-dominated, vegetated areas) within the pond were examined bimonthly between January 1997 and January 1998. Grab samples were collected randomly within the sub-habitats. Key physical environmental parameters of the sampling sites were also measured. A total of 46 species of macrobenthos was recorded: 11 polychaetes, 11 molluscs, 13 crustaceans and 11 insects. Mean species density in the five sub-habitats ranged from 0 to 3907 indm^–2, with mean biomass ranging from 0 to 96.9 gm^–2. The macrobenthos showed spatial and temporal differences among the sub-habitats and across sampling times. Species abundances of Polychaeta, Mollusca and Crustacea were significantly higher in the three open water areas than in the two vegetated (Phragmites- and Kandelia-dominated) areas, with an inverse pattern for Insecta. There were no clear temporal patterns although abundance and biomass generally increased in the cooler months. Results of a canonical correspondence analysis suggest that macrobenthic species richness, abundance and biomass in the open areas were positively correlated with salinity, while water depth, dissolved oxygen and sediment organic matter content had little relationship with the macrobenthic assemblage parameters. Ordination by multi-dimensional scaling suggests that different habitats supported distinct macrobenthic assemblages. The macrobenthic assemblage in the tidal pond was less species rich but denser than those in the neighboring tidal mangrove and mudflat, suggesting that conversion of these areas into extensively managed tidal aquaculture ponds results in reduced species richness in tropical mangrove habitats.     

Abundance, species richness and energy availability in the North American avifauna

Aim To determine how species richness, abundance, biomass, energy use and mean number of individuals per species scale with environmental energy availability in wintering and breeding avian assemblages, and to contrast assemblages of (i) common and rare species and (ii) breeding residents and migrants. To assess whether such patterns are compatible with the ‘more individuals hypothesis’ (MIH) that high‐energy areas are species‐rich because they support larger populations that are buffered against extinction. Location The North American continent (latitudinal range 23.4 °?48.1 °N; longitudinal range 124.2°?68.7° W). Methods Avian species richness, abundance, biomass and energy use were calculated for 295 Resident Bird Count plots. Environmental energy availability was measured using ambient temperature and the Normalized Difference Vegetation Index (NDVI), a close correlate of plant productivity. Analyses took plot area into account, and were conducted (with and without taking habitat type into account) using general linear models and spatial mixed models. Results Positive species–energy relationships were exhibited by both wintering and breeding assemblages, but were stronger in the former. The structure of winter assemblages responded more strongly to temperature than NDVI, while breeding assemblages tended to respond more strongly to NDVI. Breeding residents responded to annual measures of energy availability while breeding migrants and the winter assemblage responded more strongly to seasonal measures. In the winter assemblage, rare and common species exhibited species–energy relationships of a similar strength, but common breeding species exhibited a much stronger relationship than rare breeding species. In both breeding and wintering assemblages, abundance, biomass and energy use increased with energy availability and species richness. Energy availability was a poor predictor of the mean number of individuals per species. Main conclusions The nature of the species–energy relationship varies seasonally and with the manner in which energy availability is measured. Our data suggest that residents are less able to respond to seasonal fluxes in resource availability than long‐distance migrants. Increasing species richness and energy availability is associated with increasing numbers of individuals, biomass and energy use. While these observations are compatible with the MIH our data provide only equivocal support for this hypothesis, as the rarest species do not exhibit the strongest species–energy relationships.     

Relationships between fishes and habitat in rainforest streams in Sabah, Malaysia

Distinct fish assemblages were found at the mesohabitat scale in 14 streams in eastern Sabah, Malaysia. Sites were designated a priori as pool, run or riffle on the basis of physical habitat structure and properties. Principal components analysis of physical habitat data confirmed the validity of the a priori designation with a major axis of three correlated variables: water velocity, depth and substratum type. Canonical discriminant analysis on fish abundance and biomass data confirmed the existence of a specialized assemblage of fishes from riffle areas of all streams. Overall, pool and run assemblages were highly variable, dependent on stream size, but also variable between streams of the same size. Multiple regression of species richness, diversity, abundance and biomass data on principal components revealed significant but low correlations with measured habitat variables. Riffle habitats showed lower species richness and diversity but high abundance. The fish assemblage in riffles was dominated by balitorid species, specialized for fast-water conditions. Pool assemblages had the highest species diversity and were dominated by cyprinid species of a number of morphological and ecological guilds. Run assemblages were intermediate in assemblage characteristics between riffle and pool assemblages. Between-stream variation in assemblage composition was less than within-stream variation. Of 38 species collected, seven could be designated as riffle specialists, 18 as pool specialists and 13 as ubiquitous, although most of the latter showed size-specific habitat use with larger size classes found in slower, deeper water.     

福建沿岸红树林湿地多毛类生态分布

根据2009年至2012年在福建沿岸5块典型红树林湿地所作的调查资料,分析了福建沿岸红树林湿地多毛类的物种多样性、生态分布特点以及与环境因子的关系。研究区域春、秋两季共记录多毛类动物45种,其中沙蚕科、海稚虫科和小头虫科3个科种类最为丰富,种类属性为低盐或广盐性种类。多毛类平均密度和生物量分别为190个/m2和2.17 g/m2,样地×季节双因素方差分析表明,密度在不同样地间差异显著,密度和生物量的季节变化均为春季显著高于秋季。此外,林外光滩的多毛类数量要高于林内,不同样地的摄食群组成各异。红树林断面的平均种类数和多样性指数H'与沉积物粘土含量呈显著负相关,与多毛类类群的大尺度空间分布特征关联最为紧密的因子为地理纬度。     

Species richness and rarity of crane flies (Diptera, Tipuloidea) in a boreal mire

Species richness and abundance are central in biodiversity inventories and in measuring the structure of communities. Neglecting the assessment of sampling efficiency may lead to spurious estimates of species richness and conservation value. Our aim was to examine species richness, sampling effectiveness, species-abundance distribution (SAD) and rarity of a boreal, mire-dwelling crane fly (Diptera, Tipuloidea) assemblage in western Finland. 12 Malaise traps dispersed in 4 subplots and standardized sweep net samples were used to collect adult flies from the mire. A total of 23 species and 1,569 specimens were identified. In general all species richness estimators were highly correlated and indicated rather good sampling effort. Sample completeness, expressed as percentage of observed richness divided by estimated richness, was higher for mire-dwellers (mean 75 %) than for all species (mean 63 %). Crane fly assemblages of subplots and combined data fitted best with log-series SAD. Species spatial distribution was positively correlated with average abundance. In other words, the most abundant species occurred in the most of Malaise traps. Seven mire-dwelling species greatly outnumbered (94 % of the collected specimens) all other members in the assemblage, and only one observed species was rare by several definitions (local abundance, extent of occurrence in Finland and area of occupancy). Although the studied assemblage was characterized by commonness, five of the species have threatened status in Europe south of Finland. Separate species richness estimation of all species (vagrants and occasional species included) and focal species (here mire-dwellers) is supported if ecological information is available on the taxonomic group being studied.