共查询到20条相似文献，搜索用时 31 毫秒
1.
In many arid ecosystems,vegetation frequently occurs in high-cover patches interspersed in a matrix of low plant cover.However,theoretical explanations for shrub patch pattern dynamics along climate gradients remain unclear on a large scale.This context aimed to assess the variance of the Reaumuria soongorica patch structure along the precipitation gradient and the factors that affect patch structure formation in the middle and lower Heihe River Basin(HRB).Field investigations on vegetation patterns and heterogeneity in soil properties were conducted during 2014 and 2015.The results showed that patch height,size and plant-to-patch distance were smaller in high precipitation habitats than in low precipitation sites.Climate,soil and vegetation explained 82.5% of the variance in patch structure.Spatially,R.soongorica shifted from a clumped to a random pattern on the landscape towards the MAP gradient,and heterogeneity in the surface soil properties(the ratio of biological soil crust(BSC) to bare gravels(BG)) determined the R.soongorica population distribution pattern in the middle and lower HRB.A conceptual model,which integrated water availability and plant facilitation and competition effects,was revealed that R.soongorica changed from a flexible water use strategy in high precipitation regions to a consistent water use strategy in low precipitation areas.Our study provides a comprehensive quantification of the variance in shrub patch structure along a precipitation gradient and may improve our understanding of vegetation pattern dynamics in the Gobi Desert under future climate change. 相似文献
2.
In many arid ecosystems, vegetation frequently occurs in high-cover patches interspersed in a matrix of low plant cover. However, theoretical explanations for shrub patch pattern dynamics along climate gradients remain unclear on a large scale. This context aimed to assess the variance of the Reaumuria soongorica patch structure along the precipitation gradient and the factors that affect patch structure formation in the middle and lower Heihe River Basin (HRB). Field investigations on vegetation patterns and heterogeneity in soil properties were conducted during 2014 and 2015. The results showed that patch height, size and plant-to-patch distance were smaller in high precipitation habitats than in low precipitation sites. Climate, soil and vegetation explained 82.5% of the variance in patch structure. Spatially, R. soongorica shifted from a clumped to a random pattern on the landscape towards the MAP gradient, and heterogeneity in the surface soil properties (the ratio of biological soil crust (BSC) to bare gravels (BG)) determined the R. soongorica population distribution pattern in the middle and lower HRB. A conceptual model, which integrated water availability and plant facilitation and competition effects, was revealed that R. soongorica changed from a flexible water use strategy in high precipitation regions to a consistent water use strategy in low precipitation areas. Our study provides a comprehensive quantification of the variance in shrub patch structure along a precipitation gradient and may improve our understanding of vegetation pattern dynamics in the Gobi Desert under future climate change.
相似文献3.
In this study the spatial patterns and dynamics of vegetation patches along a grazing gradient in the steppe ofLarrea divaricataandStipaspp. in NE Patagonia (Argentina) are described. A general effect of grazing is the reduction of total plant cover resulting from the decrease in cover of perennial grasses (Stipa speciosa, Poa ligularis, Stipa tenuis) and some tall shrubs (Chuquiraga hystrix, Bougainvillea spinosa, Lycium chilense). Dwarf shrubs (Nassauvia fueguianaandJunellia seriphioides) increase their cover under medium and/or high grazing pressures. Plant species are spatially grouped into patches which alternate with areas of bare soil. Eleven types of vegetation patch differing in the dominant plant functional type or species, floristic richness and size were identified with different relative frequency along the grazing gradient. Based on these results, it is postulated that grazing forces the replacement of large patches dominated by tall shrubs with high species richness, byLarrea divaricatapatches or small dwarf shrub patches with low species richness and the extinction of grass patches. This results from: (1) disruption of local balances of species deletions and additions; (2) fragmentation of large patches; and (3) formation of new vegetation patches. These changes lead to differing plant spatial organization and heterogeneity along the grazing gradient which may be described by characteristic arrays of vegetation patches. 相似文献
4.
P.L. Sassi P.A. Taraborelli C.E. Borghi R.A. Ojeda 《Journal of Arid Environments》2009,73(4-5):537-541
Plant assemblages' dynamics have been studied to evaluate the influence of different environmental factors. The aim of our work was to assess the effect of a disturbance in the form of livestock grazing on annual plants, in a South American desert. We tested the exclusion of cattle grazing by comparing the composition of annual plants in three major vegetation types within a MaB Reserve in the Monte Desert of Argentina, with those of an adjacent grazed field. Sampling was conducted in two consecutive years that differed in precipitation. We established three sampling sites within each vegetation type at the reserve and the grazed field. Transects were set to assess plant cover, abundance, and richness. Theoretically, changes in diversity are explained by changes in one of its components: species richness. Species richness of annual plants was not different between the grazed and ungrazed sites. However, plant cover and diversity were lower in grazed sites, whereas abundance increased. Owing to a strong species-specific effect, we propose that it is evenness the main parameter involved in diversity dynamics in the heterogeneous vegetation mosaic of the Monte desert. Finally, vegetation types (spatial heterogeneity) and rainfall regime (temporal heterogeneity) greatly interacted with grazing effects. We endorse the idea that rapid responses of annual plant assemblages to changes in rainfall conditions coupled with herbivore control, might result in a restoration pathway for degraded arid landscapes. 相似文献
5.
In this review, we compiled published results on biological interactions at different spatial scales in the Monte desert of Argentina and identified gaps in current knowledge. We presented evidence of competitive and facilitative plant–plant conspecific and heterospecific interactions, and plant–soil–microbes interactions in relation to the abiotic environment at the fine patch-scale. We also showed evidence of animal–animal interactions and plant–animal interactions at the community scale through study cases involving both native and introduced herbivores. Moreover, we identified bottom-up and top-down forces governing the interactions between granivores (birds, ants, and small mammals) and seed availability/production at the community scale. At the landscape scale, we discussed feedbacks between domestic grazers and the spatial patterns of resources and their interrelationships with processes occurring at other scales. We concluded that research has steadily increased during the last 6 years but knowledge on biological interactions in the Monte desert is still scarce, particularly at a landscape scale. 相似文献
6.
7.
微生境尺度上放牧退化草原群落特征与土壤有机质的空间分异性 总被引：1，自引：1，他引：0
格局和过程与异质性有关。以呼伦贝尔克氏针茅草原不同放牧强度下的演替群落为对象,开展群落植被空间分布格局及土壤有机质空间异质性研究。结果显示,不同放牧强度样地群落结构和群落种类组成存在明显差异。轻度放牧样地样方内有8种植物,群落优势种为克氏针茅（Stipa krylovii）;中度放牧样地样方内有12种植物,群落优势种为糙隐子草（Cleistogenes squyarrosa）;而重度放牧样地样方内只有7种植物,群落优势种为多根葱（Allium polyrhizum）。随放牧强度的增强,植被地上生物量及其变异系数逐渐降低;土壤有机质含量表现为轻度放牧>中度放牧>重度放牧,而其变异系数表现为中度放牧>轻度放牧>重度放牧。从植被地上生物量和土壤有机质含量变异函数分析来看,随放牧压力的增大,植被地上生物量空间自相关性增强,空间异质性变大;土壤有机质含量空间分布自相关性先增强,然后减弱,空间变异性先变大,然后变小。在10 cm×10 cm的微尺度上,重牧群落植被地上生物量和土壤有机质含量之间表现出明显的相关性（P<0.05）。 相似文献
8.
This paper reports a geomorphologic landscape investigation, vegetation survey and soil sampling at 14 sites across the Gurbantunggut Desert between 87°37′09"-88°24′04"E and 44°14′04"-45°41′52′Nl. The study encountered 8 species of low trees and shrubs, 5 of perennial herbs, 8of annual plants and 48 of ephemeral and ephemeroid plants. These species of plants represent one-third of the species found in the Gurbantunggut Desert, and their communities make up a large proportion of desert vegetation with great landscape significance. In the investigation we found that the plant communities are accordingly succeeded with the spatial variation of macro-ecoenvironment.Using Principal Component Analysis (PCA) and Correlation Analysis (CA) we found that the micro-ecoenvironment heterogeneity of aeolian sandy soil′s physical and chemical properties such as soil nutrient, soil moisture, soil salt, pH etc. only impacted the diversity of herb synusia (PIEherb) of the desert, with a negative correlation. Meanwhile, the impact of microhabitat on the plant community pattern with an antagonistic interaction made vegetation′s eco-distribution in a temporary equilibrium. 相似文献
9.
QIAN Yibing WU Zhaoning ZHANG Liyun SHI Qingdong JIANG Jin TANG Lisong 《地理学报(英文版)》2004,14(4):447-455
1IntroductionStudy on the interrelationship between vegetation patterns and their habitat heterogeneity is important to recover and rehabilitate the desert vegetation, stabilize the desert ecosystem and prevent desert expansion. Domestic and foreign researchers have carried out many studies on this topic (Archer etal., 2002; Bolling etal., 2000; Chen etal., 2003; Dasti etal., 1994; Gu etal., 2002, Li etal., 2001; Li etal., 2001; Liang etal., 2003), which have used and refined statistic tech… 相似文献
10.
This paper reports a geomorphologic landscape investigation, vegetation survey and soil sampling at 14 sites across the Gurbantunggut Desert between 87o37'09'-88o24'04'E and 44o14'04'-45o41'52'N. The study encountered 8 species of low trees and shrubs, 5 of perennial herbs, 8 of annual plants and 48 of ephemeral and ephemeroid plants. These species of plants represent one-third of the species found in the Gurbantunggut Desert, and their communities make up a large proportion of desert vegetation with great landscape significance. In the investigation we found that the plant communities are accordingly succeeded with the spatial variation of macro-ecoenvironment. Using Principal Component Analysis (PCA) and Correlation Analysis (CA) we found that the micro-ecoenvironment heterogeneity of aeolian sandy soil's physical and chemical properties such as soil nutrient, soil moisture, soil salt, pH etc. only impacted the diversity of herb synusia (PIEherb) of the desert, with a negative correlation. Meanwhile, the impact of microhabitat on the plant community pattern with an antagonistic interaction made vegetation's eco-distribution in a temporary equilibrium. 相似文献
11.
古尔班通古特沙漠生境对植物群落格局的影响 总被引：16，自引：0，他引：16
沿87o37'09"~88o24'04"E纵穿古尔班通古特沙漠,对44o14'04"~45o41'52"N的范围进行11个样地的地貌景观调查、植被分布参数采集和土壤取样。研究区统计到的植物种数占古尔班通古特沙漠文献资料中植物种数的1/3,出现的植物群落构建了该沙漠大面积成片分布的荒漠植被景观。调查发现,随着宏观生境的空间变化,植物群落作相应的演替。在此基础上,利用因子分析 (PCA)和相关分析 (CA) 查明了沙漠风沙土理化属性,如土壤养分、盐分、水分、碱性 (pH) 等微生境的异质性仅对沙漠植被草本层片的多样性 (PIE草) 产生显著影响。同时,这些微生境因相互拮抗使沙漠环境处于暂时的脆弱平衡之中。 相似文献
12.
The effects of factors acting at small scale (grass/grass and grass/shrub biological interactions) and landscape scale (overgrazing and rainfall changes) on the development and permanence of banded vegetation patterns (VB) are assessed with a spatially explicit cellular automaton model. In particular, the influence of two environmental factors that are changing in many VB arid lands (rainfall and grazing pressures) is studied. Three rainfall regimes (representing 0.5, 1.0, and 2.0 times the long-term rainfall average), five grazing intensities, two types (reversible and irreversible) of grazing disturbance, two grazing periodicities (chronic and pulse), two levels of grass colonization ability, positive and negative interactions between shrubs and grasses, and the efficiency of endozoochorous seed dispersal are simulated.The results show that the permanence of undisturbed VB depends on the interaction of two factors, rainfall regime and grass colonization ability. Type and intensity of grazing also modify VB cover and permanence; furthermore, long-term overgrazing may convert mixed grass/shrub plant communities to pure scrublands dominated by endozoochorous-dispersed shrubs due to competitive interactions between shrubs and grasses.Besides providing an adequate representation of the system’s dynamics, the model is a useful tool that may be used to explore the consequences of climate change on management scenarios. 相似文献
13.
科尔沁沙地水域景观格局的时空动态——以奈曼旗为例 总被引：3，自引：0，他引：3
对位于科尔沁沙地腹地的奈曼旗近30 a来土地利用/覆被信息中水域类型的景观格局指数进行了时空组合分析。结果表明,大尺度研究区（8 135.15 km2）1975-1985年水体与湿地斑块的类型面积和数量增加,形状趋于复杂;1985-2005年斑块类型面积和数量大幅减少,形状趋于简单;中尺度研究区（892.74 km2）水体与湿地斑块的类型面积在波动中减小,湿地斑块数量减少和形状简单化的转折期相对较短且滞后于水体。小尺度研究区（110.42 km2）集中了人畜以及上游活动的干扰,水体与湿地斑块仅在个别时期出现,难以连续存在。在各尺度研究区内,河漫滩斑块类型面积变化趋势各异,数量和形状复杂程度都相对稳定;且随着研究区增大形状更加不规则。水域类型的景观格局虽然在不同时空上的动态过程存在差异性,但其发展方向具有相同趋势,发展过程受到气候波动和人类活动干扰的共同影响。 相似文献
14.
The biocontrol agent, northern tamarisk beetle (Diorhabda carinulata), has been used to defoliate non-native saltcedar (Tamarix spp.) in USA western riparian systems since 2001. Biocontrol has the potential to impact biotic communities and climatic conditions in affected riparian areas. To determine the relationships between biocontrol establishment and effects on vegetation and climate at the plot and landscape scales, we measured temperature, relative humidity, foliage canopy, solar radiation, and used satellite imagery to assess saltcedar defoliation and evapotranspiration (ET) along the Virgin River in the Mojave Desert. Following defoliation solar radiation increased, daily humidity decreased, and maximum daily temperatures tended to increase. MODIS and Landsat satellite imagery showed defoliation was widespread, resulting in reductions in ET and vegetation indices. Because biocontrol beetles are spreading into new saltcedar habitats on arid western rivers, and the eventual equilibrium between beetles and saltcedar is unknown, it is necessary to monitor trends for ecosystem functions and higher trophic-level responses in habitats impacted by biocontrol. 相似文献
15.
Great part of ecological thought in desert ecology is based on research findings in the northern hemisphere, and these have led to generalizations to other drylands. However, South American aridlands constitute an important scenario of aridland evolution in the Neotropical temperate biota. The degree of distinctiveness of the South American dryland biota is the result of the history of lineages and place (diverse topography, climates, vegetation) in the southern part of the continent since the Oligocene. The aim of our contribution is to provide an updated review of some aspects of the latest biogeographical, ecological, physiological, and behavioral research of the Monte Desert mammals and reassessment of their evolutionary ecology. The temperate Monte Desert extends from 24° to 43° south latitude and resembles parts of the North American warm deserts. The Monte is a heterogeneous mosaic of landscapes, from open sand dune habitats to Larrea shrublands and dense vegetation patches of Prosopis woodlands. The mammal assemblages show variations in richness, diversity and endemicity. The structure of mammal assemblages is closely related to vegetation structure over different spatial scales. The Monte mammal assemblages show a great diversity of niche types and ecological, physiological and behavioral attributes for desert existence, convergent, in greater or lesser degree, with ecological counterparts from other deserts of the world. We point out the need to be cautious when comparing heterogeneous arid ecosystems. 相似文献
16.
This review summarizes the effects of vegetation on runoff and soil loss in three dimensions: vertical vegetation structures(aboveground vegetation cover, surface litter layer and underground roots), plant diversity, vegetation patterns and their scale characteristics. Quantitative relationships between vegetation factors with runoff and soil loss are described. A framework for describing relationships involving vegetation, erosion and scale is proposed. The relative importance of each vegetation dimension for various erosion processes changes across scales. With the development of erosion features(i.e., splash, interrill, rill and gully), the main factor of vertical vegetation structures in controlling runoff and soil loss changes from aboveground biomass to roots. Plant diversity levels are correlated with vertical vegetation structures and play a key role at small scales, while vegetation patterns also maintain a critical function across scales(i.e., patch, slope, catchment and basin/region). Several topics for future study are proposed in this review, such as to determine efficient vegetation architectures for ecological restoration, to consider the dynamics of vegetation patterns, and to identify the interactions involving the three dimensions of vegetation. 相似文献
17.
The effects of vegetation on runoff and soil loss: Multidimensional structure analysis and scale characteristics 总被引：5，自引：0，他引：5
This review summarizes the effects of vegetation on runoff and soil loss in three dimensions: vertical vegetation structures (aboveground vegetation cover, surface litter layer and underground roots), plant diversity, vegetation patterns and their scale characteristics. Quantitative relationships between vegetation factors with runoff and soil loss are described. A framework for describing relationships involving vegetation, erosion and scale is proposed. The relative importance of each vegetation dimension for various erosion processes changes across scales. With the development of erosion features (i.e., splash, interrill, rill and gully), the main factor of vertical vegetation structures in controlling runoff and soil loss changes from aboveground biomass to roots. Plant diversity levels are correlated with vertical vegetation structures and play a key role at small scales, while vegetation patterns also maintain a critical function across scales (i.e., patch, slope, catchment and basin/region). Several topics for future study are proposed in this review, such as to determine efficient vegetation architectures for ecological restoration, to consider the dynamics of vegetation patterns, and to identify the interactions involving the three dimensions of vegetation. 相似文献
18.
Amrita G. de Soyza Justin W. Van Zee Walter G. Whitford Anne Neale Nita Tallent-Hallsel Jeffrey E. Herrick Kris M. Havstad 《Journal of Arid Environments》2000,45(4):289
Early-warning indicators of rangeland health can be used to estimate the functional integrity of a site and may allow sustainable management of desert rangelands. The utility of several vegetation canopy-based indicators of rangeland health at 32 Great Basin rangeland locations was investigated. The indicators were originally developed in rangelands of the Chihuahuan Desert. Soil resources are lost through wind and water-driven erosion mainly from areas unprotected by plant canopies (i.e. bare soil). Study sites in Idaho had the smallest bare patches, followed by sites in Oregon. The more arid Great Basin Sagebrush Zone sites in Utah had the largest bare patches. Several vegetational indicators including percent cover by vegetation, percent cover by life-form, percent cover by sagebrush, and percent cover by resilient species were negatively related to mean bare patch size and are potential indicators of Great Basin rangeland condition. Plant community composition and the range of bare patch sizes were different at sites in the three locations in Idaho, Oregon and Utah. Therefore, expected indicator values are location specific and should not be extrapolated to other locations. The condition of study sites were often ranked differently by different indicators. Therefore, the condition of rangeland sites should be evaluated using several indicators. 相似文献
19.
城市景观格局尺度效应的空间统计规律--以上海中心城区为例 总被引：33，自引：3，他引：30
以上海市外环以内的中心城区为区域背景,基于SPOT全色波段遥感影像数据和GIS技术,运用空间统计分析方法,研究城市景观格局的空间尺度效应。研究结果表明:(1)城市景观格局的空间自相关性具有显著的尺度依赖性。Moran指数I与Geary系数c对粒度变化的敏感点相同,均为50m。(2)城市景观形态具有分形特征,各类景观斑块的分维数对粒度变化的响应不同,它们随着粒度的变化呈非线性变化趋势;在粒度较小时,各类景观斑块之间的分维数差异较大,而随着粒度的增大,其分维数之间的差异逐渐缩小。(3)城市景观多样性格局,与空间区位及人类活动的空间格局息息相关。在城市中心,主导型景观是经济效益较高的商业文化景观,并且景观斑块聚集度、破碎度大;经济效益较低的农业景观分布在城市边缘区,而且景观类型单一,斑块面积较大,破碎度较小;在由城市中心向边缘过渡的中间地带,景观类型多样,空间格局复杂。(4)景观多样性具有尺度依赖性。随着幅度的增加,景观多样性指数逐渐增大,多样性的空间格局也显著变化。在0.5km幅度下,多样性指数的最大值出现在市中心,从市中心向外呈现高低起伏的环状模式扩展,随着幅度增加,多样性指数的高值区向景观类型变化最剧烈的城乡过渡地带转移。(5)景观多样性的空间变异也具有明显的尺度依赖性。在较 相似文献
20.
干旱区绿洲扩展过程中的景观变化分析 总被引：1，自引：0，他引：1
绿洲化过程中的景观变化和尺度效应是景观生态学研究的热点之一。针对这一目标以黑河中游张掖绿洲为研究区域,应用“3S”技术的缓冲分析方法,以绿洲标志景观类型农田、林地和湿地为核心,确定了不同时期绿洲范围并划分了老绿洲区和新增绿洲区。在此基础上,从景观组成动态和斑块连通度的尺度依赖特征两个方面分析了绿洲化过程中的景观变化机制和尺度效应。研究结果表明,绿洲化过程是以农田和建设用地斑块动态为主要特点。主要表现为：在不同的分区中,农田斑块以总面积和最大斑块指数增加为特点,说明农田斑块趋向集中连片分布;建设用地斑块总面积、斑块密度和最大斑块指数等3个指标都为增加,在景观上呈星点状扩张分布。老绿洲与新增绿洲的比较分析显示,新增绿洲的建设用地面积增加速率小于老绿洲,而农田面积的增加速率大于老绿洲。从景观斑块连通度的尺度依赖特点来看,在老绿洲中景观斑块类型的空间尺度依赖规律明显,但在时间尺度上的变化不显著;在新增绿洲内,林地、水域和建设用地的尺度依赖性比老绿洲高,其中林地、建设用地的空间变化规律明显,在时间尺度上无明显的差异;而水域斑块的尺度依赖性1985年高于2006年。 相似文献