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1.
Riparian plant species richness along lateral and longitudinal gradients of water stress and flood disturbance, San Pedro River, Arizona, USA 总被引：2，自引：0，他引：2
Diversity theory predicts that species numbers should be highest at intermediate levels of both disturbance and environmental stress. We examined woody and herbaceous plant species richness and cover in the San Pedro River flood plain, along lateral gradients of water availability (ground-water depth), flood disturbance (inundation frequency), and distance from and elevation above the channel, and along longitudinal gradients of water availability (ground-water depth, surface flow permanence, and rainfall) and flood disturbance (total stream power). Herbaceous species were recorded during four sampling periods, and spatial patterns for this group were time-dependent, reflecting temporal variation in limiting factors. During the summer dry season of a dry year, when overall richness was low, richness and cover of herbaceous species declined laterally from the stream channel with increasing ground-water depth, consistent with the idea that low resource levels can limit species richness. Following the summer monsoon rains and floods, when water was less limiting and annuals were seasonally abundant, lateral patterns shifted such that herbaceous species richness and cover increased with increasing plot location above or from the channel. The relationship of herbaceous species richness with tree canopy cover also varied seasonally, shifting from positive (greater richness under canopy) in dry seasons to negative (lesser richness under canopy) in wet seasons. Longitudinally, herbaceous species richness and cover were limited primarily by stream flow and/or ground-water availability during the summer dry season of a dry year. Following the summer monsoon rains and floods, patterns were weighted by the seasonally abundant annuals, and richness increased among sites primarily with distance upstream (and related rainfall gradients). Richness and cover patterns also varied between years with different flood conditions. During the two sampling seasons in the year following a large flood, herbaceous species richness increased with flood disturbance intensity but declined at the few most intensely disturbed sites, consistent with intermediate disturbance theory.For woody species, richness within plant functional groups varied in opposing ways along the lateral gradients: hydromesic pioneer species decreased and hydromesic and xeric competitors increased with distance from or above the channel, with no overall change in species richness. Among sites, woody species richness patterns were related to water availability, but not to flood disturbance. However, richness of woody hydromesic pioneer species increased with both increasing site moisture and flood disturbance. Woody and herbaceous species richness both increased among sites as a function of increasing flood-plain width, likely due to species–area effects. Overall, results indicate that flood disturbance and water availability both influence species richness of riparian plants in the flood plain of this semi-arid region river, with the relative influence of each factor varying among plant groups and over time. 相似文献
2.
JACOB BENDIX 《Geographical review》1997,87(4):468-483
ABSTRACT. Biodiversity varies considerably in Southern Californian riparian vegetation. The intermediate disturbance hypothesis posits greatest diversity in settings that are subject to moderate-intensity disturbance. Flood intensity tends to vary systematically in watersheds, potentially imposing patterns of biodiversity. In two study watersheds, species richness increases with flood severity. Diversity, or heterogeneity, is less predictable: Biodiversity patterns in these watersheds are complicated by atypical patterns of flood severity. Although riparian diversity may be intimately dependent on flood disturbance, the relationship is predictable only with due attention to the physiographic details of individual stream networks. 相似文献
3.
Linking individual behavior to spatial population processes, may clarify the complex link between species distribution and landscape properties. We asked how shrubs affect beetles in drylands and tested if we could explain distribution patterns of beetles by individual response to shrub landscape. We studied patch preference of ground-dwelling beetles segregated in a two-phase mosaic landscape, composed of shrub-covered and open patches and hypothesized that species richness and abundance are higher under shrubs due to the ameliorated microclimatic conditions and greater food resources. Pitfall trapping showed that shrub patches were preferred in shrub poor ecosystem because there was more food available under shrubs and cooler temperatures. However, similar conditions resulted in shrub preference only in an arid ecosystem, whereas in a semi-arid ecosystem, with high cover of shrubs, we found more beetles in the open patches. Observations in beetle movement patterns explained the contradicting effects of shrub patches in the two ecosystems. Beetle movement was affected by shrubs’ shading suggesting dependency on shrub structure rather than speciesdependency. Integrating analysis of beetle distribution in the population level with analysis of individual movement provides a robust framework for linking landscape properties to species behavior and distribution in a patchy landscape. 相似文献
4.
基于景观生态学方法的朝阳港潟湖湿地人类干扰强度定量评估 总被引：1，自引：0，他引：1
以朝阳港潟湖湿地为研究区,将朝阳港潟湖湿地景观类型划分为两大类七个亚类,其中自然景观主要包括河口湿地、潟湖浅滩、沼泽和盐碱荒地;人工景观主要包括养殖池、盐田和农用地。1954～2007年的50余年间,朝阳港潟湖湿地景观总体变化趋势是从大斑块、类型较单一的自然景观为主体的景观格局向小斑块、多种景观类型共同控制的景观格局转变,不同时期景观类型及其面积变化的主要驱动因素是人类活动。为了度量人类活动干扰对潟湖湿地的影响,以景观生态学为基础,构建了人类干扰强度模型方法,对1954年以来不同时期人类活动对潟湖湿地的干扰强度进行了量化分析,提出了湿地的人类干扰强度分级标准。研究结果表明,1954～1971年期间,朝阳港潟湖湿地的人类干扰强度为轻微干扰;此后,人类对潟湖湿地的干扰强度为强干扰。对比不同时期人类活动对该潟湖湿地的干扰强度,发现在1972～1983年间人类活动对该潟湖湿地的干扰强度突然增大,该潟湖湿地的开发高峰期主要是20世纪70年代至80年代初。检验结果证明,人类干扰强度模型的计算结果是可信的。 相似文献
5.
John M. Humphreys Amirsassan Mahjoor Kelly Chinners Reiss Andres Arias Uribe Mark T. Brown 《International journal of geographical information science》2020,34(8):1508-1529
ABSTRACT The modification of landscapes for agriculture, residential housing, and other human uses has the potential to alter ecosystem function, reduce native biodiversity, and to diminish the capacity of natural systems to provide essential goods and services. Resultantly, methods aimed at quantifying disturbance intensity at the intersection of anthropogenic and natural lands are important to applied aspects of landscape planning and natural resource management, as well as theoretical facets of spatial ecology. Tools to appraise human disturbance in wetlands and coastal waters are especially needed because the topographic settings of surface waters make them particularly susceptible to pollutant accumulation, hydrologic alteration, and other influences from the surrounding landscape. Assuming a water resources focus, we developed a novel geostatistical method to quantify and visualize edge effects and cumulative human disturbance for all wetlands and coastal waters in the State of Florida (USA). Model validation revealed that estimated disturbance intensity was strongly correlated to species richness, levels of heavy metal contamination, and persistent organic pollutant concentration. The presented modeling framework offers a flexible means to assess human disturbance across spatial scales and could be readily applied to prioritize conservation land acquisition and to anticipate future impacts from the proposed development. 相似文献
6.
《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(2):71-76
The Norwegian monitoring programme for agricultural landscapes is a sample-based programme that aims to document the current state and patterns of change in the agricultural landscape for the entire country. For this broad geographical coverage an indicator approach is the most cost-effective methodology. Landscape metrics are used as indicators in the monitoring programme based on the assumed importance of landscape composition and spatial pattern for a number of countryside interests. However, although indicators have been used successfully over a long period of time in various disciplines, their use in landscape monitoring is relatively new and there is little empirical data with which to assess their validity. This paper provides information on the performance of landscape diversity and landscape heterogeneity indices as estimated by specific biodiversity measures. Preliminary results show increasing numbers of breeding bird species and numbers of vascular plant species with increasing landscape diversity and heterogeneity, two indices that capture information on landscape content and structure. Overall, the heterogeneity index provided a better surrogate for species richness than the diversity index. 相似文献
7.
Hari Prasad PANDEY 《资源与生态学报(英文版)》2021,12(1):1-10
全球近四分之三的森林正在遭受人为干扰,尼泊尔三分之二以上的森林受到不同类型的干扰。在社区森林中,当地社区在生计的各个方面都依赖于森林提供的生态系统服务,这些服务以各种方式干扰森林的自然条件和生态系统的功能。本研究在尼泊尔中部丘陵区的两个社区管理森林中,研究了对植物物种多样性、更新(幼苗和树苗)、生物量、土壤有机碳(SOC)和总碳密度的主要干扰因子。以树桩数、断苗、砍伐和放牧践踏作为主要人为干扰的衡量指标,从89个随机选取的250 m2的样地中收集了必要的数据,利用广义线性模型(GLM)对人为干扰的响应进行了分析。结果表明,森林砍伐对生物量和总碳密度平衡的影响最大。森林砍伐程度越高,森林碳储量越低。SOC对上述类型的人为干扰均无显著反应。木本物种丰富度和幼树数量随着树桩数量的增加而增加,说明中间干扰是有益的。然而,较高的砍伐强度降低了幼树密度。放牧/践踏是抑制幼苗生长的最显著干扰,在践踏强度较高的森林地区,幼苗和树苗数量较少。这些结果将为尼泊尔多目标森林管理以及如何降低其他地区类似社会经济环境中的人为干扰的影响提供指南。 相似文献
8.
《The Professional geographer》2013,65(3):346-347
Mapping patterns of species richness is a longstanding tradition in biogeography and more recently in conservation planning. This paper describes the effects of sampling unit size on patterns of vertebrate richness across landscapes in the Intermountain Sagebrush and Rocky Mountain Forest ecoregions in Idaho. Variability of richness decreased with increasing size of the spatial sampling units at both sites, with greater overall variability in the forested site. Richness in the sagebrush region was best explained by alpha diversity, whereas beta diversity accounted for more of the variability in richness in the forested site. 相似文献
9.
Relationship between landscape heterogeneity and plant species richness on the Mexican Pacific coast
The present study aims to use landscape heterogeneity as a predictor of plant species richness in a tropical dry landscape area in the coast of Michoacán, Mexico. To understand the relationship between species richness and landscape, a three-step approach was followed: first, landscape spatial heterogeneity was measured by classifying landscape types according to their attributes (i.e., environmental, soil and topographic variables). Second, several diversity standard indices were used to explore biological diversity and to select the best one explaining the relationship between landscape heterogeneity and plant species richness, for this study area. Third, from the obtained results it was possible to calculate biodiversity values on the basis of landscape heterogeneity. The results indicate that it is possible to predict more than 61% of species richness through an indicator of landscape heterogeneity (H′; Shannon–Weaver diversity index). This procedure may be useful in terms of land use, conservation, and management of protected areas, mainly in areas with high biodiversity but with limited biological data, since it allows to obtain an approximation of the spatial distribution of species richness, even with scarce biological information. 相似文献
10.
Palaeolimnological records of shallow lake biodiversity change: exploring the merits of single versus multi-proxy approaches 总被引：1，自引：0，他引：1
Shallow lakes are among the most threatened ecosystems in the world and many contemporary studies have demonstrated declines in biodiversity due to anthropogenic forcing. Mostly, however, these studies have not covered the full period of human-induced diversity change in lakes which is typically over decades-centuries. Here we provide two examples of palaeoecological studies focussed on reconstructing biodiversity changes in contrasting shallow lake environments that demonstrate the efficacy of the approach—a shallow UK lake and a suite of floodplain lakes (called billabongs) in the Murray-Darling basin, Australia. In the Murray-Darling billabongs, complex sedimentary processes operate, sediment chronologies are less certain and replication of sites is needed to confirm patterns. The combination of sediment records from 10 billabongs showed that diatom diversity changes pre- and post-European (>1850) disturbance were inconsistent; however, reductions in diversity were more common and appear to reflect reductions in macrophyte abundance. At Felbrigg Lake, a multi-proxy study with strong chronological control demonstrated divergent responses of macrophyte, diatom, cladoceran and chironomid richness and diversity to a century of eutrophication. Eutrophication of the site was qualitatively inferred from changes in the macrophyte community in turn reconstructed from plant macrofossils. Benthic cladocerans showed a consistent decline in richness through the record, reflecting the gradual reduction in their macrophyte associated habitat over the past century. Diatom richness and diversity responses were complex, with increases in diversity and richness linked to both increases and decreases in macrophyte species richness and abundance. Chironomid richness and diversity patterns were less consistently linked to eutrophication. The loss of the dominant zooplanktivore (perch) in the 1970s was reflected in the richness and diversity profiles for all groups. Our study reveals clear potential for using sediment cores to infer biodiversity change in shallow lakes and shallow lake regions. However, given the contrasting patterns of diversity change for the different biological groups both in Felbrigg Lake and between Felbrigg and the billabongs, caution is required when interpreting whole-ecosystem biodiversity changes (or the absence of change) based on single as opposed to multi-proxy studies. 相似文献
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12.
漫溢补水干扰后的天然胡杨群落波动特征 总被引：2，自引：1，他引：1
以塔里木河下游荒漠河岸林中的胡杨群落为研究对象,以群落结构特征、物种多样性和优势种为群落波动的表征值,采用固定样地法对漫溢补水干扰下胡杨群落的波动响应特点进行了研究。结果表明:①干扰后胡杨群落物种组成变化明显,群落中物种数和层次呈现增加趋势,群落结构由简单向复杂转化,群落趋于稳定;②干扰前后胡杨群落物种多样性指数波动性较大,群落物种丰富度和多样性都呈增加趋势,而物种分布均匀度略有下降趋势;③漫溢补水干扰下群落中优势种的数量及种类发生改变,其中胡杨的优势度明显增大了。综上可知,地表漫溢补水植被修复措施使流域内的胡杨群落结构趋于复杂、群落层次增加,群落多样性增加,优势种及其优势度增加,总体上胡杨群落的波动为正向波动。 相似文献
13.
向海湿地景观格局变化及其原因分析 总被引：6，自引：2，他引：4
以5km为环间距,将向海湿地分割为5个同心圆。选用1980年和2000年遥感影像为基本信息源,在ARC/INFO、ERDAS8.5和FRAGSTATS3.3软件的支持下,对景观指数:斑块密度、平均斑块面积、景观多样性指数和分维数进行分析。结果表明,自20世纪80年以来,向海湿地面积萎缩、斑块破碎化。人类活动强度和自然因子变化幅度的分析表明,湿地变化是人为因子和自然因子共振迭加的结果。要保护湿地,必须控制人类对向海湿地的干扰。 相似文献
14.
物种多样性是衡量景区生态环境质量的重要指标之一。通过计算物种的多样性指数、科属、区系、生活型和生态型特征,利用除趋势对应分析方法对五台山旅游干扰下植物多样性的格局进行了研究,结果表明：在不同地理因子和物种多样性的作用下,各类植被景观区表现出一定的格局规律。在排序图上,以灌木层和草本层植物为主的Ⅲ区、Ⅳ区和Ⅶ区位于左侧,以乔木层、灌木层和草本层植物为主的Ⅰ区、Ⅱ区、Ⅵ区和Ⅴ区位于中间,仅有乔木层的Ⅸ区位于右侧。坡位、海拔和旅游影响系数与DCA第一轴和第二轴的相关性均较大,说明这3个因子对植物多样性的格局有重要影响。研究结果有益于五台山景区的生态管理。 相似文献
15.
景观格局在沙漠化研究中的作用 总被引：27，自引：5，他引：22
应用景观生态学中格局分析的一些方法对４种典型沙漠化土地景观进行了分析,研究结果表明：景观和景观中斑块的格局通过影响边界长度和组合状况,进而影响沙漠化过程中的各种生物学和生态学过程。其中,分维数的变化可以反映景观和斑块格局的变化,分维数越大格局越复杂,两者关系呈正相关;修改分维数可以反映景观格局的多样性和景观中斑块之间的相邻性,两者关系也呈正相关;沙漠化土地景观格局的数量化分析和描述,为研究沙漠化过程和景观格局的相互关系奠定了基础。同时还指出了景观格局在沙漠化危害程度判定中有重要作用。 相似文献
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旅游干扰对马仑亚高山草甸植物物种多样性的影响 总被引：5，自引：0，他引：5
在野外样带调查的基础上,以物种重要值为综合指标,分析了不同旅游干扰程度对马仑亚高山草甸植物物种多样性指数、丰富度指数和均匀度指数的影响效应及变化规律。结果表明:(1)随旅游干扰强度降低,马仑亚高山草甸的优势种披针苔草和珠芽蓼的重要值逐渐增大,而广生态幅植物蒲公英重要值却呈降低趋势。(2)中等强度的旅游干扰所形成的生境,既不会使群落种类组成有明显的变更,同时也不会抑制优势种群在群落中的重要性,从而有利于群落植物物种多样性的发展。(3)6条样带之间的群落差异系数随旅游干扰强度减弱而降小,样带1~6之间的相异性表现为逐渐递减的势态。旅游干扰强度超过了群落的自恢复能力,就会导致群落性质完全改变。上述结果为亚高山草甸旅游业的合理开发,生态环境保护和植物物种多样性保育提供了较高的理论参考和科学决策依据。 相似文献
18.
重庆岩溶区景观格局特征分析 总被引：7，自引：0，他引：7
借用景观空间格局指数分析重庆岩溶区景观格局框架, 辨识影响景观格局的驱动因素。结 果表明： 重庆岩溶区景观分布不均匀,少数几类控制着整体景观。嵌块体几何形状较复杂,被分割 程度较低,破碎化现象不明显, 空间异质化程度低。各亚区景观多样性, 均处于最大值2.81 的中 间段, 有一种或少数几种景观类型起支配地位。人工干扰程度和丰富度依I、II 和III 区地势降低 的态势而增加, 异质化程度、不均匀性和优势度则呈相反趋势。分维数差异不明显, 形状指数变幅 较大, 不同区景观嵌块体几何形状较复杂且差异悬殊。森林景观嵌块体密度和分离度按I、II 和 III 区的顺序依次增加, 耕地、园地和居民工矿用地则分别依次减少。边界密度除了III 区水域为 63.03 外, 其余都在1.82~9.14 之间。景观整体特征I 和II 区相似, 而与III 区存在显著差异。内地 质作用在大的环境背景下控制着岩溶区景观格局特征的基本框架, 外营动力在较短时空尺度上 决定岩溶区景观格局特征的纵深态势。研究可为区域岩溶景观格局调控、景观规划和生态经济的 持续发展等宏观决策提供科学依据和理论支撑, 为岩溶区区域生态安全评价积累数据基础。 相似文献
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玉龙雪山植物物种多样性和群落结构沿海拔梯度的分布格局 总被引：15，自引：0，他引：15
生物多样性沿海拔梯度的变化是多样性环境梯度格局研究中的一个热点问题。在对滇西北玉龙雪山2 900 m~4 200 m间沿海拔梯度进行的群落调查基础上,对植物物种多样性和群落结构的垂直分异格局进行了分析。结果表明:1)在16个样地中共记录植物物种261种,分属78科,158属,其中木本植物36种,灌木植物71种,草本154种。2)沿海拔梯度,森林群落的最大树高、最大胸径、平均树高和平均胸径等群落结构指标均呈单峰分布格局。3)随着海拔的升高。木本和草本的物种丰富度,先增加后下降;而灌木层的物种丰富度随着海拔的上升呈明显下降格局。4)木本层和灌木层的β多样性(Cody指数)随海拔升高,总体呈减小趋势,而草本层β多样性显示出单峰分布的垂直格局。 相似文献
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泰山景观人为干扰的程度及其影响分析 总被引：1，自引：0，他引：1
利用1986年和2001年两期TM影像,在GIS支持下,采用人为影响程度的比重和景观指数等多指标比重分析法以及人为影响类型极性分析法,对泰山景观的人为影响程度和景观结构变化作用方向进行定量描述。结果表明,人为影响类型极性分析法可以较理想地定量描述景观结构变化作用的方向和程度。在泰山风观区,景观人为综合极性影响可以划分为5个大类,影响程度可以划分为3个级别。15a来人为综合影响为正极性作用方向,其中Ⅱ级中度影响区影响系数最小,是泰山生态安全决策必须首先重视的区域。 相似文献