Lowland boreal forests characterization in Algonquin Provincial Park relative to beaver (Castor canadensis) foraging and edaphic factors

Beaver (Caster canadensis) foraging and edaphic conditions can modify the vegetational characteristics of woody plant community in lowland boreal forests. Effective management of these areas requires an understanding of the relative contribution of these factors in shaping the woody plant community structure. Our objective was to quantify the effects of herbivory by beavers and edaphic conditions on woody plant community organization of lowland boreal forests surrounding beaver ponds. Woody vegetation and soils were sampled at 15 ponds occupied by beavers and one other pond abandoned by them in southern Algonquin Park, Ontario. We measured spatial variation in plant diversity, foraging rates and sapling recruitment of trees and shrubs along gradients of beaver foraging intensity and soil moisture, P, K, Mg, and pH. Beavers fed preferentially on a small number of deciduous species and the number of cut stems declined sharply with increasing distance from ponds. Conifers increased in relative dominance to deciduous species in the presence of beavers. Plant species richness and stem and basal area diversity peaked at intermediate distances (about 25 m) from ponds. Sapling recruitment by non-preferred species was positively related to foraging intensity. Total stem abundance and basal area and sapling recruitment by four preferred species (Populus tremuloides, Acer rubrum, Acer saccharum and Corylus cornuta) were negatively related to foraging intensity. However, by including Alnus rugosa and Salix bebbiana (also preferred by beavers) these patterns changed, becoming positively related to foraging intensity. There was also a pronounced gradient in soil moisture, which also decreased with distance from ponds. The other measured edaphic variables did not vary consistently with distance from ponds. Sapling recruitment in mesic versus xeric species varied consistently with hydrid conditions along the moisture gradient, such that variation in moisture also could produce the observed pattern of plant diversity. Diversity patterns changed three years after beaver abandonment of a pond, though sapling recruitment patterns in preferred and non-preferred species around the abandoned pond were similar to the occupied ponds. These observations suggest spatial variation in woody plant richness and diversity could be determined by combined effects of both herbivory (disturbance by beavers) and variable responses of different species to edaphic conditions.     

不同水深条件下刺参养殖池塘大型底栖动物群落结构季节性变化特征

于2012年7月至2013年4月调查了荣成靖海湾3个不同水深的刺参(Apostichopus japonicus)养殖池塘内大型底栖动物的构成,以了解不同水深对刺参养殖池塘环境条件的影响以及由此引起的大型底栖生物群落结构的改变。结果表明:3个不同水深梯度池塘(1#浅水位、2#正常水位和3#高水位)底部光照强度、叶绿素a(Chla)和总有机物(TOM)含量存在显著差异,各池塘水温差异不显著。光强、Chla和TOM含量在夏季、冬季和春季均表现为1#池塘显著高于3#池塘;秋季各池塘间光强和TOM含量差异不显著,Chla含量则表现为3#池塘显著高于1#池塘。各季节3个池塘间大型底栖动物在种类组成、丰度、生物量和多样性指数上均存在显著性差异。大型底栖动物丰度和生物量夏季均表现为1#池塘显著高于3#池塘,秋季和冬季则相反;春季1#池塘丰度显著高于3#池塘,生物量则差异不显著。这些差异主要与其各自优势种及其优势度指数大小有关。大型底栖动物多样性指数夏季和秋季均表现为1#池塘高于3#池塘,春季则相反,冬季各池塘间多样性指数差异不显著。单因子相似性分析(ANOSIM)表明,各季节3个池塘间大型底栖动物群落结构均存在显著差异,表明水深梯度对刺参养殖池塘大型底栖动物群落结构造成显著性影响。相似性百分比分析(SIMPER)显示,各季节对3个池塘间大型底栖动物群落差异起主要作用的物种为各个池塘的优势种。典范对应分析(CCA)表明,水深、Chla和TOM含量为影响大型底栖动物群落的主要环境因子。     

Identifying key environmental factors related to plant and crustacean assemblages in Mediterranean temporary ponds

The current interest in Mediterranean temporary wet habitats, considered to be habitats of European Community Interest, is mainly due to their characteristic flora and fauna. Several contributions characterize each of these two components separately, but considering them simultaneously could reveal possible interactions and a more complete view of the habitat that would be useful to improve conservation measures. This paper investigates crustacean and plant assemblages in six Mediterranean temporary ponds and their relationship with several environmental variables. Significant positive relationships were found between species richness and Shannon diversity index of plant and crustacean assemblages. Crustaceans had a higher similarity among ponds than plants and, consequently, each pond had a more characteristic assemblage of plants than of crustaceans. The two groups showed a different sensitivity to environmental factors and only two factors affected both: altitude and surface area of the wet system. Disturbances (e.g. grazing by cattle) and pond size were very important for plants, whereas they were irrelevant for crustaceans. On the other hand, distance to the nearest pond, hydroperiod length, and water nitrogen were only important for crustaceans. Although similar trends on richness and diversity were observed for both biotic groups, the use of only one of them for conservation programs would not be sufficient. Our results suggest that simultaneously taking into account several community components would result in a better understanding of ecosystem functionality.     

Influence of anthropic and eco-hydrological factors on the floristic diversity of the herbaceous vegetation around the temporary ponds in Ferlo,northern Senegal

人类活动与生态水文因素对塞内加尔北部费罗临时池塘周边的草本植物区系物种多样性的影响 在萨赫勒,临时池塘在保护物种多样性方面起着重要作用。本研究考察了塞内加尔北部费罗地区的两个放牧池塘以及一个未放牧池塘,探讨了人类活动与生态水文因素对池塘周边植物多样性的影响。每个池塘建立两条植物生态样带,确定并记录每条样带上平均植被单元情况(包括植被覆盖度、土壤暴露度、土壤质地、土壤湿度和酸碱度、平均高度以及坡度等)。研究结果表明,3个池塘周边共有 草本植物22科41属55种。放牧池塘周边多为禾本科植物,尤其是画眉草属(Eragrostis tremula)与肠须草属 (Enteropogon prieurii)植物,未放牧池塘周边则主要为其他科类植物,如牛膝属(Achyranthes sp.)、鸭跖草属(Commelina forsskaolii)、黄麻属(Corchorus sp.)植物等。Wendu Marodi池塘(未放牧池塘)的香农物种多样性指数(H′)为4.9,略高于Belel Lougal池塘和Belel Sow池塘(放牧池塘),这两个池塘的香农物种多样性指数分别为4.8和4.5。3个池塘的种类平均性指数相对都较高,分别为0.85、0.83和0.78。根据生态因子可分出4个物种群：蒺藜(Tribulus terrestris)种群,集中在限牧区与过度放牧区;平枝马唐(Digitaria horizontalis)种群与孟仁草(Chloris barbata)种群,见于过度带;以及土牛膝(Achyranthes aspera)种群,生长在人类活动较少且草本植物丰富的湿地。本研究强调了维持未放牧池塘或半保护池塘与放牧池塘景观镶嵌结构的重要性,以保护塞内加尔中心与萨赫勒地区草本植物的多样性。     

Diversity of Anurans Across Agricultural Ponds in Argentina

We examined the anuran diversity of 31 ponds (30 located on the border of soybean cropland and one within a protected forest) in mid-western Entre Ríos Province (Argentina). Moreover, each species found was characterised with respect to its vertical location. Using principal component (PCA) and canonical correspondence analyses (CCA) we quantified associations between species diversity and habitat and spatial variables. A total of 21 anuran species belonging to four families (Microhylidae, Bufonidae, Leptodactylidae and Hylidae) were detected in ponds surrounded by soybean croplands. PCA generated three principal components, which together explained variation in anuran diversity across the agricultural ponds and control site. Negative values of PC-1 described the smaller ponds with narrower hedgerow and monospecific shore vegetation. PC-2 had high loading on pond depth, and PC-3 had negative loading on air temperature. CCA showed a very strong association between the two data sets. We found all guilds related with pond area. Indeed, we found that arboreal species were recorded in large ponds with higher values of shore vegetation index and presence of wider hedgerow. Moreover, a higher number of terrestrial species was found to relate to large pond areas and greater shore vegetation diversity. Finally, aquatic species were related to pond area, shore vegetation index and depth. Anuran diversity across agricultural ponds of mid-western Entre Ríos Province can be affected by local habitat factors such as reduction in pond size and depth, shore vegetation richness, width of hedgerow and air temperatures. Management of anurans to reverse recent declines will require defining high-quality habitat for individual species or group of species, followed by efforts to retain or restore these aquatic habitat. The maintenance of shore vegetation of ponds and hedgerows may increases the number of species and diversity of anurans within agricultural landscapes.     

Habitat Use by Waterbirds in Relation to Pond Size,Water Depth,and Isolation: Lessons from a Restoration in Southern Spain

Wetland restoration is increasingly important to reverse habitat degradation, recover ecosystem services, and maintain biodiversity. To aid project design, more information is required on the influence of wetland size, depth of water, and isolation on the waterbird communities that become established. During a restoration project in Doñana, one of the Europe's most important wetland complexes, an experimental network of 96 temporary ponds with standard shape but variable size, water depth, and isolation was created. We surveyed the waterbird community in spring from 2006 to 2008 and related species abundance and richness to abiotic pond characteristics. We also performed analyses pooling species by foraging guilds or body size. Waterbird abundance and species richness were highest in 2007, the wettest year when the ponds had longer hydroperiods. Larger ponds had consistently higher abundance and species richness for the entire community and for different guilds and body sizes. Moreover, the density of birds per hectare was higher in large ponds than in the smaller ones. Pond isolation and excavated depth did not affect overall abundance and richness, although opposing effects of depth were observed on some size classes, and ducks and large birds preferred isolated ponds. Some bird groups preferred ponds at a particular location. This is the first waterbird study to address the importance of pond size, depth, and isolation independently of confounding variables such as pond shape. It illustrates the varied responses from different bird groups and demonstrates the importance of varying depth, location, and isolation to enhance community abundance and diversity .     

Vegetative composition and community structure associated with beaver ponds in Canaan valley, West Virginia, USA

Beavers (Castor canadensis) can cause dramatic changes in vegetative composition and diversity. Although alterations by beaver have been studied extensively, little attention has been paid to the effects beaver impoundments have on rare plants. Effective conservation of riparian and wetland rare plant species must consider the responses of vegetation to changes in hydrology that can occur when beaver populations are present. The goal of this research was to establish the occurrence of locally rare plant species, examine community composition, and analyze vegetative community structure of vegetation associated with beaver ponds in Canaan Valley, West Virginia, USA. Species richness and diversity were similar between plots located inside beaver ponds and adjacent to beaver ponds (P > 0.05). Although no significant difference in rare plant species was detected among pond ages, the oldest ponds (>56 years) had twice as many rare species as the youngest ponds (≤6 years). The youngest ponds had higher overall mean species richness (S) than ponds 7–56 years old (P < 0.05), but S returned to similar levels in the oldest ponds. Of the 15 rare species observed, most were classified as obligate (9) or facultative wetland (4) species. The youngest ponds contained the fewest number of rare species. Multiple response permutation procedure (MRPP) analyses of community structure detected no relation between community composition and either pond age or size. However, both MRPP and non-metric multi-dimensional scaling showed proximity to pond was important in herbaceous community structure. Wetlands in beaver ponds also were shown to be distinct from adjacent wetland areas. Conservation of existing beaver populations is necessary so that the entire spectrum of pond ages is available for the maintenance of rare plant species and communities.     

Weak altitudinal pattern of overall chironomid richness is a result of contrasting trends of subfamilies in high-altitude ponds

The decline of species richness with altitude is one of the most obvious patterns in ecology and results from the combination of ecological and evolutionary mechanisms. In harsh high-altitude environments, the effect of altitude usually overrules other environmental variables related to biodiversity. Studies using species richness along altitude gradients in high altitude are relatively numerous for lakes, but not for ponds. However, due to their special features, such as small size, high isolation and regional variability, ponds have been proved to be different systems compared to lakes. In high-altitude waterbodies, species of the family Chironomidae often dominate in benthic invertebrate communities and thus serve as an ideal model to study aquatic community changes along an altitude gradient. However, due to the time-consuming processing and expertise needed to identify the species, chironomids are often excluded from regular surveys. In the present study, we sampled 66 Tatra ponds over a 1100-m altitude gradient for benthic invertebrates, with special attention to chironomids. Out of the total 122 taxa collected, Chironomidae constituted the richest group with 58 taxa, being present in all the study ponds. The most diverse pond supported 13 chironomid taxa, and mean diversity was 6 taxa/pond. While total invertebrate richness decreased with altitude, chironomid richness showed only a weak negative response to altitude. The proportion of total chironomid diversity made up of Tanypodinae and Chironominae subfamilies decreased with altitude, while the opposite trend was recorded for the proportion of Diamesinae and Orthocladiinae.     

Biodiversity–productivity relationship in ponds: Community and metacommunity patterns along time and environmental gradients

Primary production correlates with diversity in various ways. These patterns may result from the interaction of various mechanisms related to the environmental context and the spatial and temporal scale of analysis. However, empirical evidence on diversity‐productivity patterns typically considers single temporal and spatial scales, and does not include the effect of environmental variables. In a metacommunity of macrophytes in ephemeral ponds, we analysed the diversity‐productivity relationship patterns in the field, the importance of the environmental variables of pond size and heterogeneity on such relationship, and the variation of these patterns at local (community level) and landscape scales (metacommunity level) across 52 ponds on twelve occasions, over five years (2005–2009). Combining all sampling dates, there were 377 ponds and 1954 sample‐unit observations. Vegetation biomass was used as a proxy for productivity, and biodiversity was represented by species richness, evenness, and their interaction. Environmental variables comprised pond area, depth and internal heterogeneity. Productivity and species richness were not directly related at the metacommunity level, and were positively related at the community level. Taking environmental variables into account revealed positive species richness‐productivity relationships at the metacommunity level and positive quadratic relationships at the community level. Productivity showed both positive and negative linear and nonlinear relationships with the size and heterogeneity of ponds. We found a weak relationship between productivity and evenness. The identity of variables associated with productivity changed between spatial scales and through time. The pattern of relationships between productivity and diversity depends on spatial scale and environmental context, and changes idiosyncratically through time within the same ecosystem. Thus, the diversity‐productivity relationship is not only a property of the study system, but also a consequence of environmental variations and the temporal and spatial scale of analysis.     

Simple pond restoration measures increase dragonfly (Insecta: Odonata) diversity

Ponds are home to a diverse community of specialized plants and animals and are hence of great conservation concern. Through land-use changes, ponds have been disappearing rapidly and remaining ponds are often threatened by contamination and eutrophication, with negative consequences for pond-dependent taxa like amphibians or dragonflies (Odonata: Anisoptera and Zygoptera). Increasingly, restoration measures such as removal of shading terrestrial vegetation or submerged organic matter are implemented to counteract current threats, but how these measures affect the target taxa is rarely assessed. We tested if and how simple pond restoration measures affectionate diversity. We propose that pond restoration influences the light regime, which promotes aquatic and riparian vegetation important for different dragonfly life stages, thus increasing their diversity. Additionally, we assume that this changes dragonfly species composition between restored and unrestored ponds. We surveyed exuviae in the riparian and aquatic vegetation along the shore of 29 (12 restored, 17 unrestored) man-made ponds in southwest Germany and assessed environmental variables known to affect dragonfly diversity. We identified the cover of tall sedges and submerged macrophytes as the driving biotic variables for dragonfly diversity and species composition, with restoration measures affecting submerged macrophyte cover directly but tall sedges indirectly via available sunlight. This study demonstrates that simple restoration measures not only have a positive effect on overall dragonfly diversity, but also increase habitat suitability for several species that would otherwise be absent. We therefore propose dragonflies as a suitable flagship group for pond conservation.     

Plant water uptake along a diversity gradient provides evidence for complementarity in hydrological niches

Biodiversity enhances a variety of ecosystem processes, and yet the underlying mechanisms through which these relationships occur remain a critical knowledge gap. Here, we used the natural abundance of stable isotopes to measure depth of water uptake in five common grassland species (Asclepias tuberosa, Lespedeza capitata, Liatris aspera, Schizachyrium scoparium and Sorghastrum nutans) growing across an experimental grassland diversity gradient. Using this approach, we addressed the following questions: 1) does the depth‐specific provenance of water uptake differ among species and/or do interspecific differences in water source manifest with increasing community diversity? 2) Does the isotopic niche space occupied by plants change with increasing diversity? 3) Is plasticity in water uptake depth across a diversity gradient associated with functional plant responses? We found that the depth of soil water used by plants was inherently different among species when grown in monocultures. All species used less shallow soil water and more intermediate‐depth soil water in mixed assemblages than in monocultures, resulting in similar interspecific differences in water source across the diversity gradient. However, plasticity in the locations of water used were positively associated with increases in plant growth in higher diversity treatments. These results indicate that plasticity in water‐use may contribute to positive biodiversity–productivity relationships commonly observed in temperate grasslands.     

Summer zooplankton communities of selected borrow-pit ponds in Northern Illinois,U.S.A.

Zooplankton samples were collected from 7 borrow-pit ponds during the summer months of 1975 in northern Illinois. Species diversity indices and evenness values were used to characterize the ponds zooplankton community structure. Thirty-one plankton species are reported. Older borrow-pit ponds contained more species and had higher mean densities than did the newer ponds. The number of dominant species reported per pond varied from 1 to 4. Species diversity indices are higher in older ponds, and there was a general tendency for species diversity to increase with pond age. No correlations between physicochemical measurements and the structure of the zooplankton communities were found. Factors possibly governing zooplankton community structure in borrow-pits are speculated upon.     

Urban ponds as an aquatic biodiversity resource in modified landscapes

Urbanization is a global process contributing to the loss and fragmentation of natural habitats. Many studies have focused on the biological response of terrestrial taxa and habitats to urbanization. However, little is known regarding the consequences of urbanization on freshwater habitats, especially small lentic systems. In this study, we examined aquatic macro‐invertebrate diversity (family and species level) and variation in community composition between 240 urban and 782 nonurban ponds distributed across the United Kingdom. Contrary to predictions, urban ponds supported similar numbers of invertebrate species and families compared to nonurban ponds. Similar gamma diversity was found between the two groups at both family and species taxonomic levels. The biological communities of urban ponds were markedly different to those of nonurban ponds, and the variability in urban pond community composition was greater than that in nonurban ponds, contrary to previous work showing homogenization of communities in urban areas. Positive spatial autocorrelation was recorded for urban and nonurban ponds at 0–50 km (distance between pond study sites) and negative spatial autocorrelation was observed at 100–150 km and was stronger in urban ponds in both cases. Ponds do not follow the same ecological patterns as terrestrial and lotic habitats (reduced taxonomic richness) in urban environments; in contrast, they support high taxonomic richness and contribute significantly to regional faunal diversity. Individual cities are complex structural mosaics which evolve over long periods of time and are managed in diverse ways. This facilitates the development of a wide range of environmental conditions and habitat niches in urban ponds which can promote greater heterogeneity between pond communities at larger scales. Ponds provide an opportunity for managers and environmental regulators to conserve and enhance freshwater biodiversity in urbanized landscapes whilst also facilitating key ecosystem services including storm water storage and water treatment.     

Relating fish kills to upwellings and wind patterns in the Salton Sea

Awareness of pond conservation value is growing all over Europe. Ponds are recognized as important ecosystems supporting large numbers of species and several rare and threatened aquatic plants, macroinvertebrates and amphibians. Notwithstanding ponds, particularly temporary ones, are still neglected in Italy. There are some gaps in our understanding of the macrophyte ecology and the conservation value of Mediterranean small still waters. Therefore, this study investigated the macrophyte communities and physico-chemical characteristics of 8 permanent and 13 temporary ponds along the Tyrrhenian coast near Rome, with the aim to relate the distribution of aquatic plants to environmental variables, and to define the botanical conservation value of ponds. Throughout the study period (Spring 2002), Principal Component Analysis performed on abiotic variables clearly discriminated temporary ponds, smaller and more eutrophic, from permanent ponds, larger and with higher pH and oxygen concentration. A total of 73 macrophyte taxa were collected in the study ponds. Temporary waters hosted a smaller number of plant species than permanent ones. Besides hydroperiod length, the environmental factors related to plant richness were maximum depth, surface area, dissolved oxygen and nitrogen concentration in the water. Moreover, the Non-metric Multidimensional Scaling showed a high dissimilarity in the taxonomic composition of aquatic plants between temporary and permanent ponds. The former contained more annual fast-growing species (Callitriche sp. pl. and Ranunculus sp. pl.), while in the latter species with long life-cycles (i.e. Potamogeton sp. pl.) were more abundant. Our results highlighted that temporary and permanent ponds in central Italy have different macrophyte assemblages, with aquatic species (including some of conservation interest at regional scale) exclusively found in each pond type. This suggested that both type of ponds could give an irreplaceable contribution to the conservation of aquatic plant diversity of these freshwater ecosystems. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: R. Céréghino, J. Biggs, B. Oertli & S. Declerck The ecology of European ponds: defining the characteristics of a neglected freshwater habitat     

Observations on the immature Chironomidae of a polluted lowland brook-pond system (Antwerp,Belgium), aerated by the Phallus process

A lowland brook-pond system polluted by organic waste was aerated by a new aeration method (Phallus process).The immature chironomids were investigated. Forty-two species or species groups were found.The changes in community composition, species richness, diversity, redundancy, abundance and biomass were studied in the light of the recovery after treatment. Before aeration started, chironomids were absent in the aeration basin. After 81/2 months of aeration a chironomid community characterized by low species richness (four species) and high redundancy was established. Prolonged aeration resulted in a further increase of the species diversity and during the last survey, after about 2 years of aeration, the chironomid species richness had increased to 18 species. Similar trends could be found for the downstream sampling stations. The longitudinal recovery pattern probably restored the original zonation of the chironomid species, resulting from an ecological gradient created by the linear change in physiography of the water body. Orthocladiinae dominated in the brook stretch, whereas Chironominae and to a lesser extent Tanypodinae dominated in the ponds.     

Environmental correlates of plant and invertebrate species richness in ponds

Ponds (lentic water bodies <2 ha) constitute a considerable biodiversity resource. Understanding the environmental factors that underlie this diversity is important in protecting and managing the habitat. We surveyed 425 ponds for biological and physical characteristics with 78 of those also surveyed for chemical characteristics. A total of 277 invertebrate species and 265 plant species were found. Species richness varied between 2 and 99 (mean 27.2 ± 0.6 SE) for invertebrates and 1 and 58 (mean 20.8 ± 0.4 SE) for plants. Generalised additive models were used to investigate variables that correlate with the species richness of plants and invertebrates, with additional models to investigate insect, Coleoptera, Odonata, Hemiptera, Trichoptera and Mollusca species richness. Models performed reasonably well for invertebrates in general (R ² = 30.3%) but varied between lower-order invertebrate taxa (12.7–34.7%). Ponds with lower levels of shading and no history of drying contained higher numbers of species of plants and all invertebrate groups. Aquatic plant coverage positively correlated with species richness in all invertebrate groups apart from Trichoptera and the presence of fish was associated with high invertebrate species richness in all groups apart from Coleoptera. The addition of chemistry variables suggested non-linear relationships between oxygen demand and phosphate concentration and higher-order richness. We demonstrate that the composition of biological communities varies along with their species richness and that less diverse ponds are more variable compared to more diverse ponds. Variables positively correlated with richness of one taxon may be negatively correlated with that of another, making comprehensive management recommendations difficult. Promoting a high landscape-level pond biodiversity will involve the management of a high diversity of pond types within that landscape.     

A STUDY OF POND COLONIZATION BY FRESHWATER MOLLUSCS

Molluscan community diversity and composition were studied ina string of 39 ponds of uniform age and similar size, but ofvaried water chemistry, in eastern Manitoba, Canada. Speciesdistribution was examined in relation to bottom substrate, 11water chemistry parameters, macrophyte diversity and distancebetween ponds. Fifteen gastropod and 3 bivalve species werepresent in the ponds, which showed a mean mollusc species diversityof 4.3. Cluster analyses indicated that adjacent ponds wereseldom similar in community composition or water chemistry.Several species appeared to be restricted in distribution amongthe ponds by unsuitable water chemistry parameter values, themost significant of these being total dissolved solids, pH andtotal alkalinity. Stepwise multiple regression analysis identifiedtotal dissolved solids as the most important water chemistryparameter associated with mollusc diversity in the ponds, butthis factor explained only a small proportion of the total variance.The most common species had broad tolerance ranges for mostparameters while species restricted in terms of some environmentalparameters were less frequent and generally occurred at greatermean distances. The pond communities appeared to be the productof a number of environmental and biotic variables, whose relativeimportance differed among species as well as among ponds. Theelement of chance was probably important as well. (Received 15 May 1986;     

黄土丘陵区地形、土壤水分与草地的景观格局

在黄土丘陵区,地形因素和土壤水分是决定草地景观格局的主要因素,同时草地景观格局在不同尺度上影响着景观中的流.地形因素、土壤水分和草地结构在不同尺度上有着密切的联系,研究它们之间的关系对于了解生态系统的过程十分重要.针对黄土高原异质化的草地群落结构,选取黄土丘陵区经过20多年自然封育形成的天然草地,从坡面尺度对景观格局进行了调查研究,在地形因素、土壤水分和草地结构中选取了有代表性的指标14个,用多元统计分析对选取的指标进行了主成分分析和聚类分析.聚类分析将样方分成3种植被类型,不同植被类型的海拔、坡度、20～140cm土壤含水量以及物种丰富度和生物多样性存在显著性差异.相关分析表明：海拔对0～300cm土壤含水量影响显著;海拔对草地群落盖度,坡位、坡向对草地群落的物种丰富度和生物多样性有着重要影响;而草地群落的物种丰富度和生物多样性与0～100cm土层的含水量关系密切.