Diversity peaks at intermediate productivity in a laboratory microcosm

The species diversity of natural communities is often strongly related to their productivity. The pattern of this relationship seems to vary: diversity is known to increase monotonically with productivity, to decrease monotonically with productivity, and to be unimodally related to productivity, with maximum diversity occurring at intermediate levels of productivity. The mechanism underlying these patterns remains obscure, although many possibilities have been suggested. Here we outline a simple mechanism--involving selection in a heterogeneous environment--to explain these patterns, and test it using laboratory cultures of the bacterium Pseudomonas fluorescens. We grew diverse cultures over a wide range of nutrient concentrations, and found a strongly unimodal relationship between diversity and productivity in heterogeneous, but not in homogeneous, environments. Our result provides experimental evidence that the unimodal relationship often observed in natural communities can be caused by selection for specialized types in a heterogeneous environment.     

不同发育阶段阔叶红松林空间结构的初步研究

选择受到不同程度干扰的阔叶红松林群落,以空间序列代替时间序列,应用空间结构参数混交度和角尺度描述处于不同发育阶段的阔叶红松林的空间结构,结果表明由先锋树种占相对优势阶段→伴生树种占相对优势阶段→稳定群落结构阶段,群落整体的混交度不断提高;由先锋树种占相对优势阶段→伴生树种占相对优势阶段,群落的结构变化大.     

Consumer versus resource control of species diversity and ecosystem functioning

A key question in ecology is which factors control species diversity in a community. Two largely separate groups of ecologists have emphasized the importance of productivity or resource supply, and consumers or physical disturbance, respectively. These variables show unimodal relationships with diversity when manipulated in isolation. Recent multivariate models, however, predict that these factors interact, such that the disturbance diversity relationship depends on productivity, and vice versa. We tested these models in marine food webs, using field manipulations of nutrient resources and consumer pressure on rocky shores of contrasting productivity. Here we show that the effects of consumers and nutrients on diversity consistently depend on each other, and that the direction of their effects and peak diversity shift between sites of low and high productivity. Factorial meta-analysis of published experiments confirms these results across widely varying aquatic communities. Furthermore, our experiments demonstrate that these patterns extend to important ecosystem functions such as carbon storage and nitrogen retention. This suggests that human impacts on nutrient supply and food-web structure have strong and interdependent effects on species diversity and ecosystem functioning, and must therefore be managed together.     

两种类型人为干扰对城市风景林植物多样性的影响

【目的】城市化对城市森林生态系统产生巨大影响,探讨城市化背景下植物群落物种多样性成为城市生态学研究热点。笔者探究了游客活动干扰和城市园林管理干扰对物种多样性的影响,为徐州泉山保护区的生态保护提供理论基础。【方法】于2018年6月,对泉山保护区的泉山、泰山和云龙山进行野外调查,整理统计54个样方物种数据并进行物种多样性分析。【结果】人为干扰加剧了物种数的减少;两种类型人为干扰对不同层物种数影响不同;游客活动干扰对物种多样性影响显著(P<0.05),城市园林管理干扰则无显著影响(P>0.05);两种类型人为干扰对物种丰富度无显著影响(P>0.05),对均匀度影响显著(P<0.05)。两种类型人为干扰对不同层物种数影响不同,游客活动干扰增强会降低乔木层的物种数,城市园林管理干扰增强则降低灌木层的物种数;游客活动干扰对物种多样性影响显著,中度干扰下物种多样性最小,城市园林管理干扰对物种多样性无显著影响;游客活动干扰和城市园林管理干扰均未影响物种丰富度,但均影响物种均匀度,并且影响结果不同。均匀度随着游客活动干扰增强呈先减小后增加的趋势,而随着城市园林管理干扰增强呈增加的趋势。【结论】游客活动干扰较城市园林管理干扰对植物多样性格局产生更直接显著的影响,在保护中更应警惕游客的行为对植物多样性的负面影响,严格规范游客行为。     

两种不同起源华北落叶松林空间点格局及植物多样性

【目的】分析山西省黑茶山国家级自然保护区两种不同起源类型落叶松人工林和天然林径级和林层特征,并对落叶松种群空间分布点格局特征和种群对邻域物种多样性的影响效应进行研究。【方法】 采用g(r)函数点格局方法对优势种群落叶松不同生长阶段个体(小树、中树和大树)的空间分布点格局进行研究; 用单物种-面积关系模型(mISAR模型)分析样地中乔木树种对局域群落多样性的影响。【结果】两种不同起源的落叶松林内落叶松种群呈正态分布,根据林木胸径(DBH)将落叶松分为小(5 cm≤DBH<10 cm)、中(10 cm≤DBH<30 cm)、大(DBH≥30 cm)3个阶段。人工林和天然林小、中、大3个不同阶段的株数比分别为10:3:4和10:3:6,树种多样性分别为0.96、0.54、0.52和1.27、0.94、0.63。两种起源落叶松林空间点格局分布总体均表现为小尺度上的聚集分布和中大尺度上的随机分布。此外,两种起源的落叶松林内物种在调查尺度范围内均表现为单物种所有个体对邻域全部树种的丰富度起到促进作用。【结论】研究区长期的干扰使两种起源类型的落叶松林具有较为相似的水平结构和垂直结构,中径级林木个体多但小径级和大径级较少,种群难以实现世代交替。     

Long-term relationships between ecological stability and biodiversity in Phanerozoic reefs

High biodiversity has been shown to enhance ecological stability on small spatial scales and over intervals of weeks to decades. It remains unclear, however, whether this diversity-stability relationship can be scaled up to regional scales, or to longer timescales. Without empirical validation at larger scales, the implications of the diversity-stability relationship for both ecology and long-term conservation strategies cannot readily be resolved. Here I show that in biogenic reefs, ecological stability is related to taxonomic diversity on million-year timescales. The higher the mean reef diversity in a particular time interval, the smaller the change in skeletal density, style of reef building and biotic reef types in the subsequent time interval. Because the relationships apply to a wide spectrum of disturbance regimes and reef types, these results support the hypothesis that species richness itself promotes ecological stability. Carbonate production by reefs, while closely correlated with reef diversity without temporal lag, is not stabilized by reef diversity over these long timescales. This suggests that ecological stability and productivity may be decoupled in natural ecosystems.     

Spatial scale dictates the productivity-biodiversity relationship

The diversity of life is heterogeneously distributed across the Earth. A primary cause for this pattern is the heterogeneity in the amount of energy, or primary productivity (the rate of carbon fixed through photosynthesis), available to the biota in a given location. But the shape of the relationship between productivity and species diversity is highly variable. In many cases, the relationship is 'hump-shaped', where diversity peaks at intermediate productivity. In other cases, diversity increases linearly with productivity. A possible reason for this discrepancy is that data are often collected at different spatial scales. If the mechanisms that determine species diversity vary with spatial scale, then so would the shape of the productivity-diversity relationship. Here, we present evidence for scale-dependent productivity-diversity patterns in ponds. When the data were viewed at a local scale (among ponds), the relationship was hump-shaped, whereas when the same data were viewed at a regional scale (among watersheds), the relationship was positively linear. This dependence on scale results because dissimilarity in local species composition within regions increased with productivity.     

Coral cover as a proxy of disturbance:A case study of the biodiversity of the hermatypic corals in Yongxing Island, Xisha Islands in the South China Sea

The Yongxing Island is the biggest island of Xisha Islands in the middle part of the South China Sea. It occupies 1.8 square kilometers of land area and has permanent residence on it. There are only a few papers on the coral community of the Xisha Islands, reporting the species composition, structure and zonations of the hermatypic coral community in 1970s. The present study describes the hermatypic coral community based on the quadrat survey after almost 30 years in Yongxing Island in August 2002. It was the first time to present the percent cover data of live corals of Yongxing Island via a systematic scheme of quantitative quadrat sampling. The average total percent cover of the live coral is 68.4%. We found the total percent cover (TPC) could be an idea proxy of the overall disturbance regime impinging on the coral community. TPC can be used as an integrated measure of disturbance to coral reef. Using this surrogate, the best fit relation between TPC of the live corals and species richness, species diversity, or the species evenness is the unimodal second-order polymorphic parabola equation. This result is expected by the intermediate disturbance hypothesis (IDH). From the fitted parabola equations, we calculated the best TPCs corresponding to the maximal species richness, the highest species diversity, or the most evenness respectively. They are surprisingly stabilized between 55% and 58%. Coralcover is the basic parameter widely available for most observation, research or monitoring programs. The good qualitative characteristics of percent cover provide powerful tool for the experimental, theoretical and modeling studies of coral reef in response to the disturbance.     

常绿阔叶林退化群落的物种多样性特征及影响因子分析

由于土地利用方式改变以及人为砍伐等多种原因的共同作用,导致我国各地的常绿阔叶林均发生了不同程度的退化.本项研究从物种多样性角度出发,首先对浙江天童常绿阔叶林及其退化群落的α多样性进行了对比,进而利用逐步回归的方法,从9种可能影响该地区物种多样性的因子：海拔、坡度、坡向、用地类型、土层厚度、人类干扰强度、与自然植被的距离、同主要道路的距离以及距离村庄远近中,筛选出主要因子,并分析了它们对物种多样性的影响.结果表明：（1）常绿阔叶林的α多样性要显著高于退化群落;（2）对退化群落物种丰富度影响较显著的因子主要是：土层厚度、到自然植被的距离以及用地类型.其中物种丰富度与土层厚度呈正相关,与到自然植被的距离呈负相关,而废弃的人工果园、用材林中植被的物种丰富度相对另两类用地类型要高.（3）通过把前述9个因素划分为生境、景观、人类干扰三大类型后可以发现,它们对退化群落物种丰富度的作用大小存在明显差异.三大类因素对退化群落总体的物种多样性都有显著影响;对于退化的针叶林来说,主要的影响因子是生境和人类干扰;而就退化的灌丛而言,则主要是生境因素.     

干扰对草地生态系统生物多样性的影响

干扰是草地退化，沙化，盐碱化的重要原因，同时也是草地生态系统生物多样性变化的主导因子，国外关于干扰对各种植被的影响已有详细报道，但国内这方面的研究却很少，通过分析放牧，火烧，刈割，采药，水淹等干扰因子及不同干扰地草地生态系统生物多样性的影响，阐明各干扰因子及不同干扰频率的不同作用，为保护草地生物多样性及制定合理的草地利用制度提供科学依据。     

Primary forests are irreplaceable for sustaining tropical biodiversity

Human-driven land-use changes increasingly threaten biodiversity, particularly in tropical forests where both species diversity and human pressures on natural environments are high. The rapid conversion of tropical forests for agriculture, timber production and other uses has generated vast, human-dominated landscapes with potentially dire consequences for tropical biodiversity. Today, few truly undisturbed tropical forests exist, whereas those degraded by repeated logging and fires, as well as secondary and plantation forests, are rapidly expanding. Here we provide a global assessment of the impact of disturbance and land conversion on biodiversity in tropical forests using a meta-analysis of 138 studies. We analysed 2,220 pairwise comparisons of biodiversity values in primary forests (with little or no human disturbance) and disturbed forests. We found that biodiversity values were substantially lower in degraded forests, but that this varied considerably by geographic region, taxonomic group, ecological metric and disturbance type. Even after partly accounting for confounding colonization and succession effects due to the composition of surrounding habitats, isolation and time since disturbance, we find that most forms of forest degradation have an overwhelmingly detrimental effect on tropical biodiversity. Our results clearly indicate that when it comes to maintaining tropical biodiversity, there is no substitute for primary forests.     

Changes in plant community diversity and aboveground biomass along with altitude within an alpine meadow on the Three-River source region

The grassland is an important component of terrestrial ecosystems and plays a significant role in biodiversity and ecosystem functions.In the present study,the changes of plant species diversity and aboveground biomass productivity were examined along with the altitude in natural alpine grassland in the source region of three rivers on the Qinghai-Tibetan Plateau.Eleven experimental locations were selected with altitudes ranging from 3862 to 4450 m above sea level(a.s.l.).The results indicated that Kobresia pygmaea meadow,Kobresia humilis meadow and Salix cupularis shrub meadow had higher indices of diversity and aboveground biomass.The distribution of species diversity,richness and aboveground biomass showed similarly unimodal patterns across the altitude gradient with the highest indices appeared at mid-altitudes locations.The changing trend of species diversity,richness and evenness also showed significant unimodal patterns with total aboveground biomass,and the highest species diversity occurred at intermediate level of productivities.This research would provide a valuable reference for the protection of grassland biodiversity and maintaining of the grazing ecosystem function in the source region of the Three Rivers.     

Spatial scaling laws yield a synthetic theory of biodiversity.

Ecologists still search for common principles that predict well-known responses of biological diversity to different factors. Such factors include the number of available niches in space, productivity, area, species' body size and habitat fragmentation. Here we show that all these patterns can arise from simple constraints on how organisms acquire resources in space. We use spatial scaling laws to describe how species of different sizes find food in patches of varying size and resource concentration. We then derive a mathematical rule for the minimum similarity in size of species that share these resources. This packing rule yields a theory of species diversity that predicts relations between diversity and productivity more effectively than previous models. Size and diversity patterns for locally coexisting East African grazing mammals and North American savanna plants strongly support these predictions. The theory also predicts relations between diversity and area and between diversity and habitat fragmentation. Thus, spatial scaling laws provide potentially unifying first principles that may explain many important patterns of species diversity.     

甘南高寒草甸物种多样性与生产力的关系

利用甘南高寒草甸植物群落丰富度、多样性、生产力的抽样调查资料,分析了不同空间范围内物种多样性与生产力的关系,探讨了其形成机制.结果显示:丰富度、Shannon-Wiener α多样性指数、Simpson α多样性指数与生产力之问的关系在合作分站和玛曲分站均呈显著正相关,在玛曲县欧拉乡为不相关;Pielou α均匀度指数与生产力的关系在玛曲分站呈显著正相关,在合作分站和玛曲县欧拉乡均为不相关;Whittakerβ多样性指数与生产力的关系在合作分站和玛曲分站均呈负相关,在玛曲县欧拉乡为不相关.综合三个地区的数据分析表明:随着空间范围的扩大,丰富度、三种α多样性指数与生产力趋向于正相关关系,Whittakerβ多样性指数与生产力趋向于负相关关系.如果要改善甘南高寒草甸草场质量、提高草场生产力,那么不仅要保护物种多样性,还要提高物种空间分布的均匀性、减少环境异质性.     

Global biodiversity patterns of marine phytoplankton and zooplankton

Although the oceans cover 70% of the Earth's surface, our knowledge of biodiversity patterns in marine phytoplankton and zooplankton is very limited compared to that of the biodiversity of plants and herbivores in the terrestrial world. Here, we present biodiversity data for marine plankton assemblages from different areas of the world ocean. Similar to terrestrial vegetation, marine phytoplankton diversity is a unimodal function of phytoplankton biomass, with maximum diversity at intermediate levels of phytoplankton biomass and minimum diversity during massive blooms. Contrary to expectation, we did not find a relation between phytoplankton diversity and zooplankton diversity. Zooplankton diversity is a unimodal function of zooplankton biomass. Most strikingly, these marine biodiversity patterns show a worldwide consistency, despite obvious differences in environmental conditions of the various oceanographic regions. These findings may serve as a new benchmark in the search for global biodiversity patterns of plants and herbivores.     

广州市森林景观格局时空变化的研究

以TM影像和野外调查为数据源，3S为技术手段，对1985年以来广州市森林空间格局进行动态分析和综合研究。结果表明：在1985—2004年间，森林景观斑块数量增加，平均斑块面积减小，景观结构破碎化整体上有增加的趋势，主要表现为多样性指数、分维数增大，聚集度、均匀度减小，在空间和类型上局部变化不同于整体的表现；自然地理条件、人口增长、政府政策是导致景观格局变化及其区域差异的主要驱动力；随着城市扩展、农田开发等人类干扰的不断增加，森林景观生态环境保护与经济开发之间的矛盾将愈发突出。     

Biodiversity as a barrier to ecological invasion

Biological invasions are a pervasive and costly environmental problem that has been the focus of intense management and research activities over the past half century. Yet accurate predictions of community susceptibility to invasion remain elusive. The diversity resistance hypothesis, which argues that diverse communities are highly competitive and readily resist invasion, is supported by both theory and experimental studies conducted at small spatial scales. However, there is also convincing evidence that the relationship between the diversity of native and invading species is positive when measured at regional scales. Although this latter relationship may arise from extrinsic factors, such as resource heterogeneity, that covary with diversity of native and invading species at large scales, the mechanisms conferring greater invasion resistance to diverse communities at local scales remain unknown. Using neighbourhood analyses, a technique from plant competition studies, we show here that species diversity in small experimental grassland plots enhances invasion resistance by increasing crowding and species richness in localized plant neighbourhoods. Both the establishment (number of invaders) and success (proportion of invaders that are large) of invading plants are reduced. These results suggest that local biodiversity represents an important line of defence against the spread of invaders.     

Diversity and productivity peak at intermediate dispersal rate in evolving metacommunities

Positive relationships between species diversity and productivity have been reported for a number of ecosystems. Theoretical and experimental studies have attempted to determine the mechanisms that generate this pattern over short timescales, but little attention has been given to the problem of understanding how diversity and productivity are linked over evolutionary timescales. Here, we investigate the role of dispersal in determining both diversity and productivity over evolutionary timescales, using experimental metacommunities of the bacterium Pseudomonas fluorescens assembled by divergent natural selection. We show that both regional diversity and productivity peak at an intermediate dispersal rate. Moreover, we demonstrate that these two patterns are linked: selection at intermediate rates of dispersal leads to high niche differentiation between genotypes, allowing greater coverage of the heterogeneous environment and a higher regional productivity. We argue that processes that operate over both ecological and evolutionary timescales should be jointly considered when attempting to understand the emergence of ecosystem-level properties such as diversity-function relationships.     

泾河流域不同森林植被类型中物种多样性与生产力的关系

在群落样方调查基础上,采用双向指示种分析法(TWINSPAN)对子午岭地区和六盘山地区植物群落进行了数量分类.TWINSPAN将39个样方划分为7个群系.7个群系的乔木层、灌木层、草本层多样性与生产力的关系分别表现为单调下降、单调上升、不明显,群系总体多样性与生产力的关系为单调下降.     

人为干扰对城市近郊区森林植物多样性的影响——以贵阳市乌当区为例

该文研究了贵阳市乌当区马背山森林在弃耕地干扰、道路干扰、工程废弃物干扰和火干扰等4种人为干扰作用下,植物多样性的特征及其与环境因子之间的关系.结果表明:研究区域道路干扰类型的物种多样性指数最高,其次为弃耕地干扰和火干扰类型,工程废弃物干扰类型的物种多样性最低;工程废弃物干扰类型与道路干扰类型植物相似性最高,弃耕地干扰类型和工程废弃物干扰类型相似性最低.土壤结构对植物多样性的影响较大,土壤养分对植物多样性的影响不明显.各人为干扰的环境因素中,挖掘个数及面积、小路面积、岩石盖度与植物多样性和均匀度呈显著负相关,与生态优势度呈正相关.距林缘距离、枯落物盖度及高度、样地盖度等环境变量与植物多样性指数和均匀度指数呈正相关,与生态优势度呈负相关.