Effects of macroalgal species identity and richness on primary production in benthic marine communities

Plant biodiversity can enhance primary production in terrestrial ecosystems, but biodiversity effects are largely unstudied in the ocean. We conducted a series of field and mesocosm experiments to measure the relative effects of macroalgal identity and richness on primary productivity (net photosynthetic rate) and biomass accumulation in hard substratum subtidal communities in North Carolina, USA. Algal identity consistently and strongly affected production; species richness effects, although often significent, were subtle. Partitioning of the net biodiversity effect indicated that complementarity effects were always positive and species were usually more productive in mixtures than in monoculture. Surprisingly, slow growing species performed relatively better in the most diverse treatments than the most productive species, thus selection effects were consistently negative. Our results suggest that several basic mechanisms underlying terrestrial plant biodiversity effects also operate in algal-based marine ecosystems, and thus may be general.     

The factors controlling species density in herbaceous plant communities: an assessment

This paper evaluates both the ideas and empirical evidence pertaining to the control of species density in herbaceous plant communities. While most theoretical discussions of species density have emphasized the importance of habitat productivity and disturbance regimes, many other factors (e.g. species pools, plant litter accumulation, plant morphology) have been proposed to be important. A review of literature presenting observations on the density of species in small plots (in the vicinity of a few square meters or less), as well as experimental studies, suggests several generalizations: (1) Available data are consistent with an underlying unimodal relationship between species density and total community biomass. While variance in species density is often poorly explained by predictor variables, there is strong evidence that high levels of community biomass are antagonistic to high species density. (2) Community biomass is just one of several factors affecting variations in species density. Multivariate analyses typically explain more than twice as much variance in species density as can be explained by community biomass alone. (3) Disturbance has important and sometimes complex effects on species density. In general, the evidence is consistent with the intermediate disturbance hypothesis but exceptions exist and effects can be complex. (4) Gradients in the species pool can have important influences on patterns of species density. Evidence is mounting that a considerable amount of the observed variability in species density within a landscape or region may result from environmental effects on the species pool. (5) Several additional factors deserve greater consideration, including time lags, species composition, plant morphology, plant density and soil microbial effects.Based on the available evidence, a conceptual model of the primary factors controlling species density is presented here. This model suggests that species density is controlled by the effects of disturbance, total community biomass, colonization, the species pool and spatial heterogeneity. The structure of the model leads to two main expectations: (1) while community biomass is important, multivariate approaches will be required to understand patterns of variation in species density, and (2) species density will be more highly correlated with light penetration to the soil surface, than with above-ground biomass, and even less well correlated with plant growth rates (productivity) or habitat fertility. At present, data are insufficient to evaluate the relative importance of the processes controlling species density. Much more work is needed if we are to adequately predict the effects of environmental changes on plant communities and species diversity.     

Bird diversity patterns in Neotropical temperate farmlands: The role of environmental factors and trophic groups in the spring and autumn

Productivity, habitat heterogeneity and environmental similarity are of the most widely accepted hypotheses to explain spatial patterns of species richness and species composition similarity. Environmental factors may exhibit seasonal changes affecting species distributions. We explored possible changes in spatial patterns of bird species richness and species composition similarity. Feeding habits are likely to have a major influence in bird–environment associations and, given that food availability shows seasonal changes in temperate climates, we expect those associations to differ by trophic group (insectivores or granivores). We surveyed birds and estimated environmental variables along line‐transects covering an E‐W gradient of annual precipitation in the Pampas of Argentina during the autumn and the spring. We examined responses of bird species richness to spatial changes in habitat productivity and heterogeneity using regression analyses, and explored potential differences between seasons of those responses. Furthermore, we used Mantel tests to examine the relationship between species composition similarity and both the environmental similarity between sites and the geographic distance between sites, also assessing differences between seasons in those relationships. Richness of insectivorous birds was directly related to primary productivity in both seasons, whereas richness of seed‐eaters showed a positive association with habitat heterogeneity during the spring. Species composition similarity between assemblages was correlated with both productivity similarity and geographic proximity during the autumn and the spring, except for insectivore assemblages. Diversity within main trophic groups seemed to reflect differences in their spatial patterns as a response to changes between seasons in the spatial patterns of food resources. Our findings suggest that considering different seasons and functional groups in the analyses of diversity spatial pattern could contribute to better understand the determinants of biological diversity in temperate climates.     

高寒草甸不同草地群落物种多样性与生产力关系研究

生态系统的结构和功能、生物多样性与生产力的关系问题是近年来群落生态学中研究的中心问题,其中,生态系统生产力水平是其功能的重要表现形式,用4种不同草地类型探讨自然群落的物种多样性与生产力关系.结果表明,矮嵩草草甸、小嵩草草甸和金露梅灌丛群落中物种多样性与生产力的关系呈线性增加关系,藏嵩草沼泽化草甸群落中线性增加关系不显著,这表明群落生产力除受物种多样性的影响外,也受物种本身特征和环境资源的影响.不同的环境资源和环境异质性是形成群落结构特征、物种多样性分布格局差异的主要原因之一.     

Impacts of nitrogen deposition on terrestrial plant diversity: a meta-analysis in China

Aims With the global atmospheric nitrogen (N) deposition increasing, the effect of N deposition on terrestrial plant diversity has been widely studied. Some studies have reviewed the effects of N deposition on plant species diversity; however, all studies addressed the effects of N deposition on plant community focused on species richness in specific ecosystem. There is a need for a systematic meta-analysis covering multiple dimensions of plant diversity in multiple climate zones and ecosystems types. Our goal was to quantify changes in species richness, evenness and uncertainty in plant communities in response to N addition across different environmental and experimental contexts.     

降水时间对内蒙古温带草原地上净初级生产力的影响

全球气候变化下降水时间的改变将深刻影响草原生态系统地上净初级生产力(ANPP),而草原生态系统ANPP是区域碳循环的重要过程.利用1998-2007年的SPOT-VEG NDVI数据并结合111个样点的ANPP地面样方调查数据,获得了内蒙古温带草原1998-2007年的ANPP区域数据,依此分析了中国内蒙古温带草原以及区域内的3种植被类型(荒漠草原、典型草原、草甸草原)降水时间对ANPP的影响.研究结果表明,对于整个内蒙古温带草原来说,一个水分年内(从上一年9月份到当年地上生物量达最大值时的8月份)影响ANPP较为重要的降水月份为2-7月份,其中,5-7月份降水尤为重要.具体到每个月降水的影响,研究发现,7月份降水最重要,而仍处于生长季的8月份降水相对于其他生长季降水作用最小;影响不同草地类型最重要的降水时期存在一定差异,对荒漠草原和典型草原地区来说,ANPP达最大值前3个月(5-7月份)的生长季降水最重要,而8月份降水影响较小,而草甸草原地区8月份和非生长季的3、4月份降水最重要,但各个降水时期降水对ANPP的影响都较荒漠草原和典型草原小,大部分地区降水对ANPP的影响不显著.     

局域和区域过程共同控制着群落的物种多样性:种库假说

解释群落的物种多样性大小是生态学研究的一个重要的理论和实践问题。人们提出了群落物种多样性的多种假说, Zobel等人提出的种库假说(species pool hypothesis)是生物多样性理论研究的重要发展。该假说认为, 一个群落的物种多样性不仅与环境条件和生态过程(ecological process)(如竞争、捕食)有关, 也受区域种库(regional species pool)的限制。区域种库是指一个地区可进入某一群落的潜在物种数量, 它由地史过程(如冰期、地质年代)和区域过程(物种形成、迁移扩散以及消亡)所决定。按照种库假说, 某一生境类型的面积越大, 地质年代越古老, 物种形成的机会也就越多, 因而能适应和分布于该生境的物种也就越多, 实际群落中的物种丰富度也就越高。种库在空间上主要有两个层次: 区域种库和实际种库, 前者指某一生境所拥有的潜在物种数量, 主要由生物地理过程(biogeographic processes)所决定; 后者则为调查的群落中实际出现的物种数量, 主要由竞争等生态过程和区域种库共同决定。本文对种库假说的基本概念、主要内容、种库确定方法等作了介绍, 并阐述了作者对这些问题的理解和认识。     

Effects of different clipping intensities on above- and below-ground production in simulated herbaceous plant communities

We studied the effect of clipping on above- and below-ground production in different plant communities through a factorial experiment. We designed five pasture systems with different species composition, perennials/annuals ratio and soil water availability, recreating different altitudinal locations, and simulated a gradient of grazing intensity by clipping with different heights and frequencies. Response patterns of above- and below-ground production were similar, increasing with the higher clipping frequency and decreasing with altitude. These results suggest that high grazing intensity stimulate above-ground production, but only in certain situations of species composition, density, diversity, perennials/annuals ratio and water availability. This stimulus, however, is unsustainable over time, and the lower clipping frequencies are those that favour the maintenance of production.     

Human appropriation of net primary production as driver of change in landscape-scale vertebrate richness

Aim

Land use is the most pervasive driver of biodiversity loss. Predicting its impact on species richness (SR) is often based on indicators of habitat loss. However, the degradation of habitats, especially through land-use intensification, also affects species. Here, we evaluate whether an integrative metric of land-use intensity, the human appropriation of net primary production, is correlated with the decline of SR in used landscapes across the globe.

Location

Global.

Time period

Present.

Major taxa studied

Birds, mammals and amphibians.

Methods

Based on species range maps (spatial resolution: 20 km × 20 km) and an area-of-habitat approach, we calibrated a “species–energy model” by correlating the SR of three groups of vertebrates with net primary production and biogeographical covariables in “wilderness” areas (i.e., those where available energy is assumed to be still at pristine levels). We used this model to project the difference between pristine SR and the SR corresponding to the energy remaining in used landscapes (i.e., SR loss expected owing to human energy extraction outside wilderness areas). We validated the projected species loss by comparison with the realized and impending loss reconstructed from habitat conversion and documented by national Red Lists.

Results

Species–energy models largely explained landscape-scale variation of mapped SR in wilderness areas (adjusted R²-values: 0.79–0.93). Model-based projections of SR loss were lower, on average, than reconstructed and documented ones, but the spatial patterns were correlated significantly, with stronger correlation in mammals (Pearson's r = 0.68) than in amphibians (r = 0.60) and birds (r = 0.57).

Main conclusions

Our results suggest that the human appropriation of net primary production is a useful indicator of heterotrophic species loss in used landscapes, hence we recommend its inclusion in models based on species–area relationships to improve predictions of land-use-driven biodiversity loss.     

Patterns of floristic richness in vegetation communities of California: regional scale analysis with multi-temporal NDVI

Aim Applying water‐energy dynamics and heterogeneity theory to explain species richness via remote sensing could allow for the regional characterization and monitoring of vegetation community assemblages and their environment. We assess the relationship of multi‐temporal normalized difference vegetation index (NDVI) to plant species richness in vegetation communities. Location California, USA. Methods Sub‐regions containing species inventories for chaparral, coastal sage scrub, foothill woodland, and yellow pine forest communities were intersected with a vegetation community map and an AVHRR NDVI time series for 1990, 1991, 1992, 1995 and 1996. Principal components analysis reduced the AVHRR data to three variables representing the sum and temporal trajectories of NDVI within each community. A fourth variable representing heterogeneity was tested using the standard deviation of the first component. Quadratic forms of these variables were also tested. Species richness was analysed by stepwise regression. Results Chaparral, coastal sage scrub, and yellow pine forest had the best relationships between species richness and NDVI. Richness of chaparral was related to NDVI heterogeneity and spring greenness (r² varied between 0.26 and 0.62 depending on year of NDVI data). Richness of coastal sage scrub was nonlinearly related to annual NDVI and heterogeneity (r² 0.63–0.81), with peak richness at intermediate values. Foothill woodland richness was related to heterogeneity in a monotonic curvilinear fashion (r² 0.28–0.35). Yellow pine forest richness was negatively related to spring greenness and positively related to heterogeneity (r² 0.40–0.46). Main Conclusions While NDVI's relationship to species richness varied, the selection of NDVI variables was generally consistent across years and indicated that spatial variability in NDVI may reflect important patterns in water‐energy use that affect plant species richness. The principal component axis that should correspond closely with annual mean NPP showed a less prominent role. We conclude that plant species richness for coarse vegetation associations can be characterized and monitored at a regional scale and over long periods of time using relatively coarse resolution NDVI data.     

基于净初级生产力的中国生态足迹产量因子测算

生态足迹作为一种非货币化的生态系统评估工具,是近年来国际上一种重要的判别可持续发展程度的生物物理量方法。产量因子是生态足迹计算中的一个重要参数,其准确与否直接影响到计算结果的可靠性与可比性。随着生态足迹方法的广泛应用,其标准化和本地化成为迫切需要。为了便于区域水平上的生态足迹空间分析,本文采用中国2001年1kmMODIS数据,根据植被的净初级生产力,计算出全国和不同省份各种土地类型的产量因子。结果表明:就中国产量因子而言,由于中国农地生产力水平高于全球平均水平,其产量因子为1.74,而其余几种类型土地的产量因子均<1,分别为林地0.86,畜牧地0.51,渔场0.74;就不同省份而言,由于区域内不同土地利用类型的相对生产能力不同,产量因子各不相同。     

大别山南坡森林植物群落物种多样性及其与海拔因子的关系

大别山地区植物资源丰富,区系组成复杂且起源古老,为连接华东、华北和华中三大植物区系的纽带,也是我国重要的生物多样性保护和水源涵养生态功能区。采用样方法,在大别山南坡的多枝尖、庵基坪和麒麟沟3个地区,沿着不同海拔高度选取了具有代表性的森林植物群落进行研究,从不同植物群落类型和层次的物种多样性、均匀度和丰富度及其与海拔因子的关系等方面,对大别山南坡的森林植物群落物种多样性进行综合分析。结果表明:1. 共记录有植物108科270属449种,划分为20个森林植物群落类型;2. 森林植物群落各层次物种丰富度表现为草本>乔木>灌木;Shannon-Wiener多样性指数和Simpson多样性指数呈现出乔木>灌木>草本;Pielou均匀度指数变化较为复杂;3. 森林植物群落各层次的物种丰富度随海拔升高而下降;Shannon-Wiener指数和Simpson指数也表现为随着海拔升高而下降,但草本层在1400m之后有上升的趋势。Pielou指数在乔木层中表现为随着海拔的升高而下降,在草本层中表现为先下降后出现上升,在灌木层中则随着海拔的升高而上升,但其波动更为剧烈。本研究对大别山南坡森林植被大范围的采样观测研究,能够全面的展现大别山南坡森林植物的种类分布、空间组成等整体概况及其与海拔因子的关系,能为以后大别山南坡生物多样性的保护提供较为全面真实的数据,从而为大别山地区生物多样性的保护和可持续利用提供理论依据和实践意义。     

Species richness and canopy productivity of Australian plant communities

The species richness (number of vascular plants per hectare) of Australian plant communities (containing a mosaic of gap, regeneration, maturation and senescent phases) is correlated with the annual biomass productivity of the overstorey canopy.The annual production of leaves and stem in the canopy of the plant community is shown to be limited by the requirements of photosynthesis (particularly light and the availability of water) and the length of the growing season.The species richness of Australian plant communities is the product of the blance between the dominance of the overstorey and the response of the understorey to the shading of the overstorey. For all climatic regions and zones the species richness of the overstorey of the plant community is shown to be exponentially related to the annual shoot growth of the overstorey canopy, until the latitudinal or altitudinal tree line is reached. With latitudinal increase outside the tropics, overstorey canopies of forest communities absorb increasingly more of the incident solar radiation. markedly reducing the species richness of the understorey strata. In contrast, in these latitudes the overstorey of plant communities with widely spaced trees or tall shrubs will absorb far less solar radiation, thus enabling the species richness of the understorey to be maintained.     

Seasonality regulates the effects of resource addition on plant diversity and ecosystem functioning in semi-arid grassland

季节性调控资源添加对半干旱草原物种多样性与生态系统功能的影响在资源富集的条件下,物种丰富度、群落地上生产力以及群落稳定性的季节变化通常被忽视。本研究致力于探究在干旱区草原,资源添加如何在生长季的不同月份影响物种丰富度、群落地上生产力及其稳定性。我们在内蒙古草原设置了为期3年的资源添加(氮添加-N、水添加-W以及水、氮共同添加-NW)实验,利用季节性取样的方法,去检验资源添加(水、 氮)对物种丰富度、群落地上生产力及其稳定性的影响,并通过构建结构方程模型分析资源添加调控不同月份与整个生长季群落稳定性的内在机制及其相对重要性。研究结果表明,资源添加在整体上未改变5与6月的群落地上生产力,而氮与水氮共同添加显著提高了7与8月的群落地上生产力。资源添加在整体上未改变物种丰富度、物种异步性与群落稳定性。氮添加与水氮共同添加提高了7与8月的群落地上生产力,主要源于其增加了多年生丛生禾草的地上生产力。结构方程模型分析表明：在生长季前期与整个生长季,物种异步性是决定群落稳定性的主要机制;在生长季后期,多年生丛生禾草的稳定性是驱动群落稳定性的主要因子。我们的研究证明：在半干旱草原,季节与资源的有效性可以交互影响群落地上生产力及其稳定性。这些发现对于半干旱草原的季节性可持续管理具有重要意义,以期减轻土地利用与全球变化带来的影响。     

物种多样性和功能群多样性与生态系统生产力的关系——以内蒙古短花针茅草原为例

生物多样性与生态系统生产力之间的关系是当前生态学领域的热点问题。短花针茅(Stipa breviflora)草原是内蒙古荒漠草原的主要类型, 生态系统脆弱, 气候波动剧烈, 研究内蒙古短花针茅草原生物多样性与生产力的关系具有十分重要的意义。该研究在内蒙古短花针茅草原区设置了202个样地进行群落调查, 在干旱区及半干旱区两种资源供给下, 分析了物种丰富度、功能群丰富度与生产力的关系, 旨在解决两个科学问题: 1)物种多样性和功能群多样性中, 哪一种与生产力关系更为密切?2)资源供给对多样性和生产力关系的影响。结果表明: 1)物种丰富度、群落生产力与年降水量呈正相关关系, 而功能群丰富度与年降水量之间不存在显著相关性; 2)群落生产力随物种丰富度的增加而增加, 且两者间呈正线性关系, 功能群丰富度与生产力之间不存在显著相关关系; 3)资源供给会影响多样性与生产力之间的关系, 资源供给低时, 多样性对生产力贡献较低, 资源供给高时, 多样性对生产力的贡献较高。该研究丰富了多样性与生产力关系的研究, 同时, 考虑到植物功能性状的研究在近几年受到生态学家的重视, 且多数研究集中于小尺度的人工控制实验, 因此, 在大尺度自然生态系统中开展功能性状多样性与生态系统功能关系的研究将十分必要。