边缘效应的空间尺度与测度

综述了边缘效应的空间尺度类型以及在不同尺度上的测度方法.基于大量的研究整合,认为边缘效应空间尺度的划分,可以根据空间尺度的不同以及边缘效应形成和维持因素,分为大中小3个尺度类型,即大尺度的生物群区交错带、中尺度的景观类型之间的生态交错带和小尺度的斑块(生态系统)之间的群落交错区.大尺度主要是以植被气候带为标志的生物群区间的边缘效应,这种地带性的交错区主要受大气环境条件的影响.中尺度类型主要包括城乡交错带、林草交错带、农牧交错带等类型,是不同生态系统要素的空间交接地带,在物质能量等相互流动的作用下变得更为复杂.小尺度水平上是指斑块之间的交错所形成的边缘效应,受小地形等微环境条件及生物非生物等因子的制约,研究主要集中在群落边缘、林窗边缘和林线交错带等方面.对边缘效应测度的定量化研究有助于更加深入理解边缘效应.在大尺度水平上,边缘效应测度的研究主要是应用数量生态学等方法,研究不同气候带之间界线的划分及其物种分布的梯度规律性.中尺度水平上应用景观生态学的3S技术等方法,侧重于研究交错带的动态变化趋势及位置宽度的判定.小尺度水平上通过对距离边缘的长度,各群落中种群的数量、结构、多样性等定量指标的测定来构建测度公式,从而对边缘效应的强度进行量化,并反映边缘对群落的正负效应.总体上看,主要集中于中小尺度上,未来应该强化大尺度边缘效应测度的研究.     

Evidence on ecotone concepts from switch,environmental and anthropogenic ecotones

Abstract. Four contrasting ecotones were sampled to address three questions: (1) Are there ‘ecotonal’ species, (2) Do ecotones possess higher (or lower) species richness than the adjacent communities? and (3) Are exotic species more likely to occur in ecotones? One ecotone was edaphic, one was apparently caused by a positive‐feedback switch, one was environmental/anthropogenic and one was entirely anthropogenic. The exact position of each ecotone was established from the spatial change in ordination scores. Ecotonal species, in the sense of species mainly restricted to the ecotone at the site, were present in all four ecotones. All but one of the ecotonal species were native. The switch ecotone and the purely anthropogenic ecotone also contained native species that were significantly more frequent in the ecotone than in either adjacent community. Species richness was intermediate between that of the two adjacent communities in three of the ecotones. In the environmental/anthropogenic ecotone, species richness was higher than in adjacent communities, but not significantly so. There were appreciable numbers of exotic species in the two ecotones with anthropogenic influence, one of which had a proportion of exotic species intermediate between the two adjacent communities. Contrary to theory, the proportion of exotic species in the second ecotone was significantly lower than in either adjacent community. We conclude that all three features we examined depend on the particular ecological conditions and the ecology of the species present; they are not intrinsic properties of ecotones.     

Properties of ecotones: Evidence from five ecotones objectively determined from a coastal vegetation gradient

Abstract. Several properties have been suggested to be characteristic of ecotones, but their prevalence has rarely been tested. We sampled five ecotones to seek evidence on seven generalizations that are commonly made about ecotones: vegetational sharpness, physiognomic change, occurrence of a spatial community mosaic, many exotic species, ecotonal species, spatial mass effect, and species richness higher or lower than either side of the ecotone. The ecotones were in a sequence from scattered mangroves, through salt marsh, rush‐marsh, scrub, woodland, to pasture. We developed a method to objectively define, by rapid vegetational change, the position and depth of an ecotone, identifying five ecotones. Their positions were consistent across three sampling schemes and two spatial grain sizes. One ecotone is a switch ecotone, produced by positive feedback between community and environment. Another is anthropogenic, due to clearing for agriculture. Two others are probably environmental in cause, and one may be largely a relict environmental ecotone. Sharp changes in species composition occurred. Three ecotones were associated with a change in plant physiognomy. In two, the ecotone was located just outside a woodland canopy, in the zone influenced by the canopy. Community mosaicity was evident at only one ecotone. There were few strictly ecotonal species; many species occurred more frequently within ecotones than in adjacent vegetation, but there were never significantly more ecotonal species than expected at random. There was little evidence for the spatial mass effect reducing ecotonal sharpness, or leading to higher species richness within ecotones. Species richness was higher than in the adjacent habitat in only one ecotone. It seems that supposedly characteristic ecotone features depend on the particular ecological situation, and the ecology of the species present, rather than being intrinsic properties of ecotones.     

生态交错带及其研究进展

生态交错带研究对探索自然生态规律和保护环境有重要意义。近30a来,有关生态交错带的论文数平均年增57%,显示其得到了愈来愈广泛的关注。回顾了生态交错带概念的产生与发展,区分了它与边缘、生态边界层与生态过渡带等概念的异同;简述了其7个基本属性,即高生物多样性、丰富的特有种、大量外来种、频繁的物质流动、敏感的时空动态性、结构的异质性和脆弱性;总结提炼了生态交错带的基本原理和假说;综述了生态交错带的生物多样性产生机制、对全球变化的响应与反馈、生态设计与管理以及生态交错带模型发展和整合的研究进展。提出今后需要大力发展理论研究、多尺度模型转化和多因子综合分析,以完善生态交错带理论并支持生态学机理的探索。     

长白山林区森林/沼泽交错群落的植物多样性

本研究应用样带网格调查方法,对森林／沼泽交错区上6种群落的植物多样性状况、优势种类与分布以及交错区环境梯度进行了研究。结果表明：森林／沼泽交错区植物多样性具有沿着交错区环境梯度逐渐增高的趋势;发育成熟的交错群落具有最高的植物多样性,且高于相对应的典型森林群落。由于交错区群落存在着沼泽植物类群、森林类群以及交错区群落的优势种类群,故发育成熟的交错区群落种类较丰富,一些优势种种群数量为森林中的5倍。因为交错区的生境对于满足这些种类的生活史具有重要作用。森林／沼泽交错群落的特征与交错区环境梯度以及两个植被类型的特征密切相关。     

Birds at the urban fringe: avian community shifts in different peri-urban ecotones of a megacity

Cities can be regionalized in intra-urban and peri-urban areas. The space between urban areas and adjacent systems represents an ecological transition that often acts as a semi-permeable biological filter. In this study, we assessed changes in avian community species richness, density, and composition at different peri-urban ecotones (i.e., urban-croplands, urban-grasslands, urban-shrublands) of northeastern Mexico City. Species richness was lower in the urban component of urban-grassland and urban-shrubland ecotones, while bird densities were higher in the urban components of the urban-grassland and urban-shrubland peri-urban ecotones, mainly due to the high number of urban exploiter species. However, the urban-cropland peri-urban ecotone exhibited a different pattern, with similar low bird species richness and density values between both components (urban and non-urban). A species composition analysis revealed that urban bird communities were not influenced by adjacent non-urban habitats, since the urban components of peri-urban ecotones were more similar among them than in relation to the rest of non-urban components. In summary, results of this study show that urbanization can represent an important biological filter for birds, often reducing species richness and homogenizing avian communities at local scales. As the environmental variables determining ecological processes related to the semi-permeable filter effect that urban areas pose to biodiversity might depend on urban habitats, regions, and spatial scales, further studies are needed to fully understand this phenomenon.     

Notes on ecotone attributes and functions

We attempt to identify general properties of ecotones. Earlier attempts to do so encountered difficulties resulting from contradictory conceptions of ecotones. Thus, we begin with and center our discussion on a definition of ecotone. The definition is complex. It includes scaling, structural, and functional aspects. Based on this complex definition, we offer a brief review of what is an ecotone, what attributes it has, and how it influences other habitats of interest. We identify feedback as a possibly important but ignored function of ecotones. This discussion is presented in general terms which apply to a variety of ecological situations. We point out that results of an evaluation of ecotone attributes largely depends on the spatial and temporal scale at which ecotone is conceptualized and data are collected. We suggest that some of ecotone determinants scale naturally in a repeatable fashion among various aquatic systems. Finally, we point to the concentration of dynamic properties of ecotones as applied to land/water interface.     

城市景观多样性的空间尺度分析——以上海市外环线以内区域为例

景观生态学研究的就是某一空间尺度范围内的景观格局与生态过程。因为景观格局与生态过程中存在的尺度多样性 ,导致尺度成为理解景观格局和生态过程相互作用的关键 ,其已经成为景观生态学的一个重要概念 ,但是由于理论和方法的限制 ,对景观生态学的尺度研究还不够 ,特别是景观格局综合性指标在不同幅度上的变化特征和效应。在 GIS与 RS技术支持下 ,采用基准分辨率为 5 m的 SPOT遥感图像作为数据源 ,对不同幅度下的城市景观多样性的空间分布格局进行了分析 ,并进一步利用半变异函数对其空间异质性进行定量描述。结论揭示 :随着空间尺度的增加 ,景观多样性程度也不断增加 ,另外多样性的空间分布格局也具有显著变化 ,由于受城市发展历史和目前城市扩展方向的影响 ,多样性在总体上是不平衡的 ,尺度越大 ,不平衡越明显 ;不同尺度下景观多样性空间格局的变化 ,与城市景观的特点和城市景观的功能息息相关 ,不过其受经济效益和社会文化效益的影响更大 ;随着尺度增加由于掩盖了更小尺度上的变异 ,导致块金效应增强 ,空间自相关部分对系统总的变异则明显下降 ;景观多样性具有尺度依赖性 ,可以说景观多样性也是尺度的函数 ,在不同的尺度上 ,结果差异显著 ,所以在景观生态学的研究中绝对不能忽略尺度对格局的影响     

Rapid Turnover and Edge Effects in Dung Beetle Assemblages (Scarabaeidae) at a Bolivian Neotropical Forest-Savanna Ecotone1

Habitat fragmentation and the widespread creation of habitat edges have recently stimulated interest in assessing the effects of ecotones on biodiversity. Ecotones, natural or anthropogenic, can greatly affect faunal movement, population dynamics, species interactions, and community structure. Few data exist, however, on insect community response to forest–savanna ecotones, a natural analog to anthropogenically cleared areas adjacent to forest. In this study, the abundance, total biomass, average individual biomass, and distribution of scarabaeine dung beetles were examined at a sharp tropical evergreen forest–savanna ecotone in Santa Cruz, Bolivia. The abundance, total biomass, and average individual biomass of dung beetles varied significantly across the forest, edge, and savanna habitats. Species richness (S_obs) also varied significantly across the three habitats, but statistical estimations of true species richness (S_est) did not. Habitat specificity of the dung beetles in this study was extremely high. Of the 50 most common species collected during the study, only 2 species were collected in both the forest and savanna habitats, signaling nearly complete community turnover in just a few meters. Strong edge effects were evidenced by the decline in abundance, total biomass, and species richness at the forest‐savanna boundary.     

栖息地破碎化与鸟类生存

栖息地破碎化给野生动物带来的不良后果是全球生态学家和保护生物学家共同关心的问题.自从提出栖息地破碎化是导致生物多样性丧失的关键因素之一的论点后,近20年来,栖息地破碎化研究一直是生态学和保护生物学最活跃的前沿研究领域之一.栖息地破碎化是一动态过程,可在多尺度上发生并蕴涵着复杂的空间模式变化.栖息地破碎化对鸟类的生态学效应主要体现在面积效应、隔离效应和边缘效应等.这些效应影响着鸟类的分布、基因交流、种群动态、扩散行为、种间关系和生活史特征等,最终影响着鸟类的生存.介绍和总结了栖息地破碎化过程、研究的理论依据及栖息地破碎化对鸟类生存产生的诸多影响.     

半干旱区湿地-干草原群落交错带边缘效应研究

以宁夏盐池四儿滩湿地为例,于2005年和2006年7~8月份沿湿地—干草原生境梯度按东、东北、西、西北4条样线进行实地植被调查,并采用TWINSPAN数量分类和植物群落结构指数计量研究湿地—干草原交错带边缘效应。结果表明:(1)四儿滩湿地生态系统植物群落分为沼泽植被、草甸植被、干草原植被3个类型。(2)四儿滩湿地植物群落结构指数除群落均匀度指数外,生态优势度、丰富度和物种多样性均是交错带最大,其次是旱生带,湿生带最小。(3)四儿滩湿地—干草原交错带不同方向群落结构差异较大,各项植物群落结构指数均是东北样线最大,西北样线最小。造成不同样线间边缘效应差异的主要因素是人为干扰程度和地形抬升程度不同。     

A new method to infer vegetation boundary movement from ‘snapshot’ data

Global change may induce shifts in plant community distributions at multiple spatial scales. At the ecosystem scale, such shifts may result in movement of ecotones or vegetation boundaries. Most indicators for ecosystem change require timeseries data, but here a new method is proposed enabling inference of vegetation boundary movement from one ‘snapshot’ (e.g. an aerial photograph or satellite image) in time. The method compares the average spatial position of frontrunners of both communities along the vegetation boundary. Mathematical analyses and simulation modeling show that the average frontrunner position of retreating communities is always farther away from a so‐called optimal vegetation boundary as compared to that of the expanding community. This feature does not depend on assumptions about plant dispersal or competition characteristics. The method is tested with snapshot data of a northern hardwood‐boreal forest mountain ecotone in Vermont, a forest‐mire ecotone in New Zealand and a subalpine treeline‐tundra ecotone in Montana. The direction of vegetation boundary movement is accurately predicted for these case studies, but we also discuss potential caveats. With the availability of snapshot data rapidly increasing, the method may provide an easy tool to assess vegetation boundary movement and hence ecosystem responses to changing environmental conditions.     

Estimating the ecotone width in patchy ecotones using a sigmoid wave approach

Ecotones are zones of transition between two adjacent ecological systems and are characterized by a high rate of change compared to these adjacent areas. They are dynamic entities with both a spatial and temporal property, reflected in an ecotone width and location, which vary across time during succession or environmental change on both a local or global scale. Various techniques have been proposed to characterize ecotones, one of them being a sigmoid wave curve fit on the transects across the ecotone. In this paper, we test the robustness of a sigmoid wave model approach on simulated ecotone data with a varying degree of steepness, patchiness and transect length. An analysis of variance (ANOVA) provided us details on the sensitivity of the estimated ecotone width for the steepness, the transect length as well as for the patchiness of the ecotone. The statistics also allowed us to investigate the interaction between the different parameters on the resulting ecotone width. We conclude that the sigmoid wave curve-fitting algorithm provides a robust way to describe ecotones with various degrees of steepness and patchiness. Depending on the transect window size used, a sigmoid wave curve-fitting algorithm will pick up variations in ecotone steepness or in ecotone steepness and patchiness.     

Metacommunity versus Biogeography: A Case Study of Two Groups of Neotropical Vegetation-Dwelling Arthropods

Biogeography and metacommunity ecology provide two different perspectives on species diversity. Both are spatial in nature but their spatial scales do not necessarily match. With recent boom of metacommunity studies, we see an increasing need for clear discrimination of spatial scales relevant for both perspectives. This discrimination is a necessary prerequisite for improved understanding of ecological phenomena across scales. Here we provide a case study to illustrate some spatial scale-dependent concepts in recent metacommunity studies and identify potential pitfalls. We presented here the diversity patterns of Neotropical lepidopterans and spiders viewed both from metacommunity and biogeographical perspectives. Specifically, we investigated how the relative importance of niche- and dispersal-based processes for community assembly change at two spatial scales: metacommunity scale, i.e. within a locality, and biogeographical scale, i.e. among localities widely scattered along a macroclimatic gradient. As expected, niche-based processes dominated the community assembly at metacommunity scale, while dispersal-based processes played a major role at biogeographical scale for both taxonomical groups. However, we also observed small but significant spatial effects at metacommunity scale and environmental effects at biogeographical scale. We also observed differences in diversity patterns between the two taxonomical groups corresponding to differences in their dispersal modes. Our results thus support the idea of continuity of processes interactively shaping diversity patterns across scales and emphasize the necessity of integration of metacommunity and biogeographical perspectives.     

Hydrogeomorphic Controls on Reduction–Oxidation Conditions across Boreal Upland–Peatland Interfaces

The reduction–oxidation (redox) state of peatland pore waters plays an important role in many peatland biogeochemical processes. Recent research has also shown that the interface between ecosystems, or the ecotone, may be responsible for a disproportionate amount of biogeochemical activity when material and/or energy is hydrologically transported between ecosystems. The purpose of this research was to examine the spatiotemporal dynamics of redox conditions across two geomorphically distinct Boreal Precambrian Shield upland–peatland ecotones to determine the spatial and temporal scales at which these ecotones may be important. Pore water chemistry of iron and sulphur species was monitored across two upland–peatland ecotones in northwestern Ontario in conjunction with hydrological measurements under both stormflow and nonstormflow conditions. In addition, one upland–peatland ecotone was instrumented to make continuous measurements of in situ redox potential (Eh) over a 12-day period to determine whether measurements at a high temporal scale could provide additional insights into the transfer of nutrients across the upland–peatland interface. Results indicated that hydrology—specifically, groundwater flowpath and the strength of the hydrological connection between upland and peatland—determined the spatial extent of the ecotone as a biogeochemical hotspot. In situ Eh measurements showed that these ecotones may be most important over a scale of only several hours and are largely affected by lateral hydrological flows from the upland. The role of both hot spots and hot moments in biogeochemistry must be considered to accurately estimate the ability of a single ecosystem to process chemical inputs.     

Phylogenetic and morphological relationships between nonvolant small mammals reveal assembly processes at different spatial scales

The relative roles of historical processes, environmental filtering, and ecological interactions in the organization of species assemblages vary depending on the spatial scale. We evaluated the phylogenetic and morphological relationships between species and individuals (i.e., inter‐ and intraspecific variability) of Neotropical nonvolant small mammals coexisting in grassland‐forest ecotones, in landscapes and in regions, that is, three different scales. We used a phylogenetic tree to infer evolutionary relationships, and morphological traits as indicators of performance and niche similarities between species and individuals. Subsequently, we applied phylogenetic and morphologic indexes of diversity and distance between species to evaluate small mammal assemblage structures on the three scales. The results indicated a repulsion pattern near forest edges, showing that phylogenetically similar species coexisted less often than expected by chance. The strategies for niche differentiation might explain the phylogenetic repulsion observed at the edge. Phylogenetic and morphological clustering in the grassland and at the forest interior indicated the coexistence of closely related and ecologically similar species and individuals. Coexistence patterns were similar whether species‐trait values or individual values were used. At the landscape and regional scales, assemblages showed a predominant pattern of phylogenetic and morphological clustering. Environmental filters influenced the coexistence patterns at three scales, showing the importance of phylogenetically conserved ecological tolerances in enabling taxa co‐occurrence. Evidence of phylogenetic repulsion in one region indicated that other processes beyond environmental filtering are important for community assembly at broad scales. Finally, ecological interactions and environmental filtering seemed important at the local scale, while environmental filtering and historical colonization seemed important for community assembly at broader scales.     

中国东北样带生物群区及其对全球气候变化响应的初步探讨

 本文应用室内模拟与野外实地调查相结合的方法,对中国东北森林草原样带上生物群区及其过渡带的位置与面积进行了判定,并预测了未来全球变化条件下生物群区及过渡带可能的变化趋势。结果表明：中国东北样带内的生物群区和过渡带可由基于气候数据和Ho1dridge方法的数量模型较确切地判定出,与实际调查的结果吻合较好。在未来气候变化下,过渡带面积呈扩大化趋势;森林区对降水量的变化反应敏感;草原区地理分布位置变动很大,但其相对面积变化较小;荒漠灌丛对全球变化的反应最为剧烈。     

Ecotone formation through ecological niche construction: the role of biodiversity and species interactions

Rapid changes in species composition, also known as ecotones, can result from various causes including rapid changes in environmental conditions, or physiological thresholds. The possibility that ecotones arise from ecological niche construction by ecosystem engineers has received little attention. In this study, we investigate how the diversity of ecosystem engineers, and their interactions, can give rise to ecotones. We build a spatially explicit dynamical model that couples a multispecies community and its abiotic environment. We use numerical simulations and analytical techniques to determine the biotic and abiotic conditions under which ecotone emergence is expected to occur, and the role of biodiversity therein. We show that the diversity of ecosystem engineers can lead to indirect interactions through the modification of their shared environment. These interactions, which can be either competitive or mutualistic, can lead to the emergence of discrete communities in space, separated by sharp ecotones where a high species turnover is observed. Considering biodiversity is thus critical when studying the influence of species–environment interactions on the emergence of ecotones. This is especially true for the wide range of species that have small to moderate effects on their environment. Our work highlights new mechanisms by which biodiversity loss could cause significant changes in spatial community patterns in changing environments.     

土壤微生物群落构建理论与时空演变特征

土壤微生物作为陆地生态系统的重要组成部分,直接或间接地参与几乎所有的土壤生态过程,在物质循环、能量转换以及污染物降解等过程中都发挥着重要作用。对土壤微生物时空演变规律及其形成机制的研究,不仅是微生物演变和进化的基础科学问题,也是预测微生物及其所介导的生态功能对环境条件变化响应、适应和反馈的理论依据。讨论了土壤微生物群落的定义、测度方法和指标,认为群落是联系动植物宏观生态学与微生物生态学的基础,群落构建机制是宏观和微观生态学都需要研究的核心科学问题;从生态学的群落构建理论出发,阐述了包括生态位理论/中性理论、过程理论和多样性-稳定性理论在土壤微生物时空演变研究中的应用,以及微生物群落在时间和空间上的分布特征及其尺度效应;确立了以微生物群落构建理论为基础、不同时空尺度下土壤微生物群落演变特征为主要内容的微生物演变研究的基本框架。     

尺度与密度:测定不同尺度下的种群密度

群落中的种群密度由于空间尺度的变化而存在着一定差异,那么,某一种群的密度随着空间尺度的变化会发生怎样的变化?抑或某一物种相对于另一物种而言,随着空间尺度的变化其密度会怎样变化?这是与尺度有关的种群密度问题,当属生态学的基本问题.该文提出这样的问题,并把不同尺度下的种群密度称之为尺度密度(scale density).O-Ring函数的实质是计算不同尺度下的种群密度.因此,在研究实例中,应用O-Ring函数计算了典型草原处于不同恢复阶段的羊草(Leymuschinensis)种群、米氏冰草(Agropyron michnoi)种群,以及米氏冰草种群相对于羊草种群在不同尺度下的种群密度,结果发现:羊草和米氏冰草2个种群的尺度密度,在小尺度范围内严重退化群落均高于恢复演替群落,这一结果验证了“胁迫梯度假说”,同时表明该结果是放牧胁迫下正相互作用所致;通过比较羊草种群与米氏冰草相对于羊草的尺度密度发现,在严重退化的群落中,羊草与米氏冰草的种间关联为负联结,这种负联结是由正相互作用引起的,而在恢复8年和恢复21年群落中,二者之间是正联结,当为竞争所致.该实例说明分析种群密度随尺度变化的规律对于深入认识生态学问题可能会有很大帮助.