徐州城市景观格局对绿地植物多样性的多尺度影响

城市地表景观的变化导致城市生物栖息地的损坏、破碎和丧失,致使城市生物多样性下降.为探讨城市景观格局变化对植物多样性的影响,本研究以徐州市绕城高速公路内的城区为对象,采用布朗布伦奎特(Braun-Blanquet)盖度等级法对36块城市绿地植物群落进行调查,并对不同绿地植物群落的物种多样性进行了分析.同时,以研究区2005和2015年的Landsat ETM遥感影像作为基础数据源,在Erdas、GIS、Fragstats软件的支持下,以每块调查样地为中心,分别建立9个不同半径的缓冲区,计算各缓冲区内表征斑块形状、破碎度和连通性共3类39个景观指数,在此基础上,运用冗余分析(RDA)筛选出不同幅度下对城市绿地植物多样性有显著影响的景观格局指数.结果表明: 植物多样性对景观整体格局和景观要素的响应具有明显的时间和空间尺度效应.2005年,未利用地和农田的破碎度、形状指数在800 m半径的缓冲区内能更好地解释植物多样性,建筑用地的破碎度和连通性指数在800～2000 m范围内对植物多样性有重要影响;2015年,草地和林地景观在800 m缓冲区内可更好地解释植物多样性,而建筑用地和未利用地在1000～2000 m范围内对植物多样性有显著影响;研究区当前植物多样性受2005年类型水平景观指数的影响更显著,说明研究区植物多样性对周边景观格局变化的响应存在一定的时间滞后;景观水平的格局指数与类型水平指数特征较为一致,说明物种与空间尺度的相互作用更多依赖于景观类型.     

Factors influencing herpetofauna abundance and diversity in a tropical agricultural landscape mosaic

Agricultural intensification and the associated factors, including land transformation, are among the major global threats affecting biodiversity especially herpetofauna. However, little information is available about how different factors shape herpetofauna species assemblages in agricultural landscape at different spatial scales from patch (125 – 250m) to the landscape (500 – 1000m). We assessed the diversity of amphibians and reptiles in areas under low and high degrees of agricultural intensification and explored different factors regulating diversity at different spatial scales using four sampling methods. Diversity and abundance of amphibians varied significantly between the two zones, but not for reptiles. Agricultural intensification index (AII), calculated based on agrochemical use and area under agriculture at 250m scale, seemed to affect amphibians both at patch as well as at 500m and 1000m landscape scales. The AII influenced reptilian diversity only at patch and 500m scales. Vicinity of natural forest had a stronger influence on reptilian abundance. Seminatural vegetation impacted herpetofauna diversities at larger spatial scales. The extent of water bodies influenced the reptilian abundance at 250m patch scale and amphibian abundance both at 250m and 1000m scale. Fallow lands affected only reptilian diversity at all spatial scales. Plantation affected amphibian at all scales but reptiles only at the landscape scale. Habitat heterogeneity regulated only amphibian diversity. These results highlight the fact that different patch and landscape-scale factors regulate the diversity of reptiles and amphibians differentially. Such scale-specific information will crucially inform future conservation action for the herpetofauna in the agricultural landscape.     

不同干扰背景下景观指数与物种多样性的多尺度效应——以巩义市为例

以黄河中下游山地丘陵区的巩义市为研究区,采用典型样地法对灌草丛、人工林和农田边缘3种不同干扰背景下的自然、半自然生境内的植物进行调查。基于景观生态学原理,在地理信息系统技术支持下,借助于Fragstatta3.3软件,以调查样地为中心,计算了150、250、500、750、1000、1250、1500m不同半径缓冲区内表征景观形状(Edge and patch shape)、边缘对照(Edge contrast)、相似度和邻近度(Proximity and similarity)、景观多样性(Diversity)、基质(Texture)、斑块大小和密度(Patch size and patch density)共6类52个指数,运用冗余分析(RDA)筛选出不同尺度下对该区农业景观中植物多样性有显著影响的景观指数。结果表明:不同尺度,景观指数对物种多样性的影响变化显著。灌草丛生境,在500—750m范围内,SHAPE_AM指数和PARA_AM指数能够很好的解释物种多样性,解释量为33.6%;人工林生境,SHAPE_AM指数、AREA_CV指数、SIMI指数和PAFRAC指数在1000—1250m范围内对物种多样性的解释量达到48.1%;农田边缘生境,GYRATE_CV指数、ENN_CV指数、PARA_MN指数和FRAC_AM指数在750—1250m范围内对物种多样性影响显著,解释量为32%。其中,辛普森多样性指数(SIDI)与灌草丛物种多样性在750—1250m范围内作用显著,ENN_CV指数仅对农田边缘物种多样性影响较大。景观指数对物种多样性的影响具有尺度依赖性,未来应全面综合探讨这些指数的尺度效应及在景观生态学中的应用。     

城市化景观格局对本土植物多样性的多尺度影响——以北京市顺义区为例

景观格局对植物多样性的影响已经在很多研究中得到了验证,但有关城市景观的影响仍然知之甚少。为了探究城市化景观格局对植物多样性的影响及其尺度效应,本研究在北京市顺义区调查了105个样地,计算每个样地的α和β多样性指数;并以100 m为步长,分析了100～1000 m范围内的10个尺度43个城市的景观格局指数。结果表明: 在所有尺度上,城市景观面积指数、核心类指数和边缘指数与本土植物多样性均呈负相关;形状复杂性指数在小尺度内有利于植物多样性,而面积加权复杂性指数则在较大尺度上影响明显。其他指数如城市斑块的连接性、邻近性、内聚性、破碎性和散布并列指数与本土植物多样性之间的关系轻微且不稳定。城市化强度与尺度呈负相关,与各个尺度的植物多样性呈负相关。合理将城市区域分为许多边缘简单的小斑块,能够更好地保护本土植物多样性。该研究提出了保护城市植物多样性的景观格局建议,为生态城市建设提供参考。     

Broad‐scale patterns in plant diversity vary between land uses in a variegated temperate Australian agricultural landscape

Plant diversity is threatened in many agricultural landscapes. Our understanding of patterns of plant diversity in these landscapes is mainly based on small‐scale (<1000 m²) observations of species richness. However, such observations are insufficient for detecting the spatial heterogeneity of vegetation composition. In a case‐study farm on the North‐West Slopes of New South Wales, Australia, we observed species richness at four scales (quadrat, patch, land use and landscape) across five land uses (grazed and ungrazed woodlands, native pastures, roadsides and crops). We applied two landscape ecological models to assess the contribution of these land uses to landscape species richness: (i) additive partitioning of diversity at multiple spatial scales, and (ii) a measure of habitat specificity – the effective number of species that a patch contributes to landscape species richness. Native pastures had less variation between patches than grazed and ungrazed woodlands, and hence were less species‐rich at the landscape scale, despite having similar richness to woodlands at the quadrat and patch scale. Habitat specificity was significantly higher for ungrazed woodland patches than all other land uses. Our results showed that in this landscape, ungrazed woodland patches had a higher contribution than the grazed land uses to landscape species richness. These results have implications for the conservation management of this landscape, and highlighted the need for greater consensus on the influence of different land uses on landscape patterns of plant diversity.     

Scale-dependent relationships between landscape structure and microclimate

This paper examined the scale-dependent relationships between landscape structure (e.g., slope, elevation, and overstory canopy coverage) and microclimate (e.g., air and soil temperatures and soil moisture) at different spatial scales along a 10050 m transect in the Southeastern Missouri Ozarks, USA. The landscape structure and microclimate variables were measured every 10 m along the transect during the growing season, June to September, 1996. We used the simple correlation analysis and "moving window" technique (no overlap between two adjacent windows) to examine the correlation coefficients between landscape structure and microclimate variables at scales or window sizes from 10 m to 2000 m. Because the sample size decreased rapidly in the "moving window" method, we also used the standardized cross-variogram to investigate the relationships between landscape structure and microclimate variables at a larger range of scales from 10 m to 8000 m. We found that the relationships between landscape structure and microclimate were apparently scale-dependent along the transect, suggesting the interactions between landscape structure and microclimate were stronger at some scales than others. The landscape structure variables were poor in explaining the variation of each microclimate variable at fine scales (e.g., 10 m). The correlations between elevation and microclimate variables were, in general, significantly improved with the increase of scales, while the improvement was less significant for slope and canopy coverage. Of the landscape structure variables, elevation, in general, had a higher correlation with the microclimate variables than slope and overstory canopy coverage at most scales examined. Our results suggest that small scales (e.g., < 100 m) are not suitable to study the relationships/interactions between landscape structure and microclimate and larger scales (e.g., > 500 m) are more appropriate though the relationships vary at the larger scales. Both the simple correlation analysis and standardized cross-variogram analysis were effective and, in general, consistent in characterizing the scale-dependent relationships between landscape structure and microclimate. Meanwhile, the standardized cross-variogram had the advantage to examine the relationships at large scales over the correlation analysis because the sample size reduced rapidly in the correlation analysis.     

Monitoring shifts in plant diversity in response to climate change: a method for landscapes

Improved sampling designs are needed to detect, monitor, and predict plant migrations and plant diversity changes caused by climate change and other human activities. We propose a methodology based on multi-scale vegetation plots established across forest ecotones which provide baseline data on patterns of plant diversity, invasions of exotic plant species, and plant migrations at landscape scales in Rocky Mountain National Park, Colorado, USA. We established forty two 1000-m² plots in relatively homogeneous forest types and the ecotones between them on 14 vegetation transects. We found that 64% of the variance in understory species distributions at landscape scales were described generally by gradients of elevation and under-canopy solar radiation. Superimposed on broad-scale climatic gradients are small-scale gradients characterized by patches of light, pockets of fertile soil, and zones of high soil moisture. Eighteen of the 42 plots contained at least one exotic species; monitoring exotic plant invasions provides a means to assess changes in native plant diversity and plant migrations. Plant species showed weak affinities to overstory vegetation types, with 43% of the plant species found in three or more vegetation types. Replicate transects along several environmental gradients may provide the means to monitor plant diversity and species migrations at landscape scales because: (1) ecotones may play crucial roles in expanding the geophysiological ranges of many plant species; (2) low affinities of understory species to overstory forest types may predispose vegetation types to be resilient to rapid environmental change; and (3) ecotones may help buffer plant species from extirpation and extinction.     

三峡库区消落带外来植物入侵与景观基质组成结构的关联性

外来物种入侵过程不仅受入侵地生境的影响,也受到周边景观基质的影响.厘清景观基质对外来入侵物种的影响,对于外来物种的入侵管控具有重要意义.本研究针对长江三峡库区消落带植物群落开展调查,评估三峡库区消落带外来植物入侵现状;在岸线以上(含消落带)2000 m范围内划分出10个景观格局尺度,采用14个指标分析景观基质组成结构;...     

Effects of landscape and patch attributes on the functional diversity of medium and large-sized mammals in the Brazilian Cerrado

The Cerrado ecoregion, although threatened, holds an important diversity of medium- and large-sized mammals, which play considerable ecological functions. However, the functional diversity of medium- and large-sized mammals is considerably affected by landscape characteristics. Thus, we inventoried medium- and large-sized mammals in nine patches (natural forest remnants) in the Cerrado ecoregion of central Brazil and investigated the influence of patch and landscape attributes (buffer with 5 km around patch) on their functional diversity. We surveyed these species from August 2016 to January 2017 through camera trapping and active search techniques (tracks, vocalizations, and burrows). Functional diversity was calculated based on body mass, behavior (presence or absence of social behavior), type of locomotion, dietary habits, and environmental sensitivity. For analysis, we divided species into two groups: forest dependent mammals (FDM) and forest non-dependent mammals (NDM). We used Akaike’s information criterion corrected for small sample size to select the models that best explain the functional diversity at the local (patch) and landscape scales. The FDM species were influenced by Normalized Difference Vegetation Index (NDVI) and patch size at the patch scale and by mean patch size and edge density at the landscape scale. The NDM were not influenced by patch and landscape scale attributes. Our results indicated that analyses at two scales with the mammal species grouped considering their differences in dependence of forest remnants is a valid approach for evaluating diversity patterns of medium-and large-sized mammals in the Brazilian Cerrado ecoregion.

     

Scale-specific correlations between habitat heterogeneity and soil fauna diversity along a landscape structure gradient

Habitat heterogeneity contributes to the maintenance of diversity, but the extent that landscape-scale rather than local-scale heterogeneity influences the diversity of soil invertebrates—species with small range sizes—is less clear. Using a Scottish habitat heterogeneity gradient we correlated Collembola and lumbricid worm species richness and abundance with different elements (forest cover, habitat richness and patchiness) and qualities (plant species richness, soil variables) of habitat heterogeneity, at landscape (1 km²) and local (up to 200 m²) scales. Soil fauna assemblages showed considerable turnover in species composition along this habitat heterogeneity gradient. Soil fauna species richness and turnover was greatest in landscapes that were a mosaic of habitats. Soil fauna diversity was hump-shaped along a gradient of forest cover, peaking where there was a mixture of forest and open habitats in the landscape. Landscape-scale habitat richness was positively correlated with lumbricid diversity, while Collembola and lumbricid abundances were negatively and positively related to landscape spatial patchiness. Furthermore, soil fauna diversity was positively correlated with plant diversity, which in turn peaked in the sites that were a mosaic of forest and open habitat patches. There was less evidence that local-scale habitat variables (habitat richness, tree cover, plant species richness, litter cover, soil pH, depth of organic horizon) affected soil fauna diversity: Collembola diversity was independent of all these measures, while lumbricid diversity positively and negatively correlated with vascular plant species richness and tree canopy density. Landscape-scale habitat heterogeneity affects soil diversity regardless of taxon, while the influence of habitat heterogeneity at local scales is dependent on taxon identity, and hence ecological traits, e.g. body size. Landscape-scale habitat heterogeneity by providing different niches and refuges, together with passive dispersal and population patch dynamics, positively contributes to soil faunal diversity. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Top-down effects of foraging decisions on local,landscape and regional biodiversity of resources (DivGUD)

Foraging by consumers acts as a biotic filtering mechanism for biodiversity at the trophic level of resources. Variation in foraging behaviour has cascading effects on abundance, diversity, and functional trait composition of the community of resource species. Here we propose diversity at giving-up density (DivGUD), i.e. when foragers quit exploiting a patch, as a novel concept and simple measure quantifying cascading effects at multiple spatial scales. In experimental landscapes with an assemblage of plant seeds, patch residency of wild rodents decreased local α-DivGUD (via elevated mortality of species with large seeds) and regional γ-DivGUD, while dissimilarity among patches in a landscape (ß-DivGUD) increased. By linking theories of adaptive foraging behaviour with community ecology, DivGUD allows to investigate cascading indirect predation effects, e.g. the ecology-of-fear framework, feedbacks between functional trait composition of resource species and consumer communities, and effects of inter-individual differences among foragers on the biodiversity of resource communities.     

Canopy cover type,and not fine-scale resource availability,explains native and exotic species richness in a landscape affected by anthropogenic fires and posterior land-use change

Anthropogenic fires and land-use change, including the conversion from native to exotic species canopies, are two major types of disturbances that strongly affect the functioning of forest ecosystems around the world. These disturbances alter the resource availability for plants, which may lead to changes in species richness. Here we examined the relative effects of canopy cover type, light availability and soil nutrient (N and P) availability on species richness, including invasive species, at different post-fire plant systems. Additionally, we tested the resource heterogeneity hypothesis (RHH) for plant diversity, which proposes that diversity is higher in habitats with spatially heterogeneous resources. We evaluated four different canopy cover types, including mature and second-growth Nothofagus pumilio forests, treeless prairie, Pinus sylvestris afforestations, all of which were converted from mature N. pumilio forests. Using generalized mixed-effects model correlations, we determined (1) the relative influence of canopy cover type, light and soil nutrient availability on understory species richness and (2) the relationship between species richness and resource heterogeneity. We found that canopy cover type was the factor that best explained species richness, much more than fine-scale light and soil nutrient availability. Additionally, we found that the more homogeneous the light environment the higher the number of exotic species (mainly found in the prairie where the highest light intensity occurred), which is contrary to what the RHH states. In conclusion, canopy cover type, a stand-scale driver, and not fine-scale resource (light, N and P) availability, was most important for explaining native and exotic (including invasive) species understory richness in a landscape affected by anthropogenic fires and posterior land-use change.     

Spatio‐temporal analysis of the relationship between landscape structure and the olive fruit fly Bactrocera oleae (Diptera: Tephritidae)

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Affinities and high-order diversity within landscape mosaics

Summary Concepts and methods for use in the study of plant community variation across a single landscape, or for the comparative analysis of two or more landscapes, are presented. The method is called affinity analysis because it produces a sorting and scaling of all the communities in a data set according to degree of differentiation in composition away from an objectively identified subset of modal communities. Modal communities possess maximum affinity with the whole landscape because they contain a large number of the species common throughout the landscape. The modal communities provide a kind of central tendency for the landscape and an anchor for depicting the dispersion of all other communities in it.To accomplish affinity analysis, the Jaccard similarity coefficient and the WilcoxonT statistic are used in a two-step transformation of the primary species-by-site data matrix. From these calculations we obtain both a visual image, theS-T graph, and summary statistics for the landscape-wide diversity described by the data. One summary statistic is a high-order diversity measure for the total patchwork of communities. We refer to this measure as mosaic diversity. The analytical results are referred to collectively as the metastructure because they provide a general, abstract, characterization of any set of community data. This abstract rendering of the data allows comparison of pattern and variation between taxonomically, geographically, and temporally different landscapes. Either presence/absence or abundance data may be used.Examples using artificial and field data are presented. All but one of the field data sets showed a significantly higher mosaic diversity than would be expected from a randomly constructed landscape. We also show how the new methods may be used with ordination to explore intralandscape patterns in more detail than was previously possible.In addition to statistical matters, ecological and evoutionary interpretations of affinity analysis are discussed. Topics included in this discussion involve reasoning about the influences on diversity arising from micro- and macroevolution, species packing and association, environmental gradients, differential fitness expression among species-populations, continuity in community variation, and the uses of both presence/absence and abundance data in community studies. Among the examples provided, mosaic diversity is independent of diversity (Whittaker, 1972).     

Scale dependent drivers of wild bee diversity in tropical heterogeneous agricultural landscapes

Factors associated with agricultural intensification, for example, loss of seminatural vegetation and pesticide use has been shown to adversely affect the bee community. These factors may impact the bee community differently at different landscape scales. The scale dependency is expected to be more pronounced in heterogeneous landscapes. However, the scale‐dependent response of the bee community to drivers of its decline is relatively understudied, especially in the tropics where the agricultural landscape is often heterogeneous. This study looked at effects of agricultural intensification on bee diversity at patch and landscape scales in a tropical agricultural landscape. Wild bees were sampled using 12 permanent pan trap stations. Patch and landscape characteristics were measured within a 100 m (patch scale) and a 500 m (landscape scale) radius of pan trap stations. Information on pesticide input was obtained from farmer surveys. Data on vegetation cover, productivity, and percentage of agricultural and fallow land (FL) were collected using satellite imagery. Intensive areas in a bee‐site network were less specialized in terms of resources to attract rare bee species while the less intensive areas, which supported more rare species, were more vulnerable to disturbance. A combination of patch quality and diversity as well as pesticide use regulates species diversity at the landscape scale (500 m), whereas pesticide quantity drove diversity at the patch scale (100 m). At the landscape scale, specialization of each site in terms of resources for bees increased with increasing patch diversity and FL while at the patch scale specialization declined with increased pesticide use. Bee functional groups responded differentially to landscape characteristics as well as pesticide use. Wood nesting bees were negatively affected by the number of pesticides used but other bee functional groups were not sensitive to pesticides. Synthesis and Applications: Different factors affect wild bee diversity at the scale of landscape and patch in heterogeneous tropical agricultural systems. The differential response of bee functional groups to agricultural intensification underpins the need for guild‐specific management strategies for wild bee conservation. Less intensively farmed areas support more rare species and are vulnerable to disturbance; consequently, these areas should be prioritized for conservation to maintain heterogeneity in the landscape. It is important to conserve and restore seminatural habitats to maintain complexity in the landscapes through participatory processes and to regulate synthetic chemical pesticides in farm operations to conserve the species and functional diversity of wild bees.     

遥感影像空间分辨率及粒度变化对城市景观格局分析的影响

尺度是景观生态学和遥感领域的重要问题,已有研究主要考虑景观的粒度效应,很少涉及遥感影像空间分辨率对景观格局,尤其是对城市景观格局的影响.基于2000年和2002年分别由ETM 和IRS-PAN影像解译得到的土地利用图,从景观和类型两个层次分析了不同粒度下上海市一城市化样带的景观格局.结果表明,城市景观有明显的尺度效应,空间分辨率和粒度变化都会影响城市景观格局,而道路等线性廊道对尺度变化的敏感则是造成这一影响的主要原因.斑块密度、边界密度、平均斑块分维度、景观聚集度和最大斑块指数的粒度效应比较明显,而景观比例、Shannon多样性指数对粒度变化并不敏感.高分辨率影像适用于城市景观格局,尤其是破碎度的分析,其用于分析的合适粒度是5～10m.     

Land-use diversity index: a new means of detecting diversity at landscape level

Preservation of ecological diversity is a guiding principle of landscape management and planning. Although diversity is often quantified with measurable indices, common approaches used to measure diversity, for example the Shannon–Weaver index, are not adequate for many landscape studies, because they are affected by scale and sampling efforts. A robust index for measurement of landscape diversity should be able to quantify distinctive components of a landscape mosaic. This paper provides a new diversity index for landscape studies that improves the measurement of diversity at landscape level. The key features of the method are inclusion of an implication of physical moment and quantification of diversity by placing greater weight on the structure and composition of a patch. We have named the new index the land-use diversity index, or LUDI, and have concluded that the LUDI is the preferred measure of diversity at landscape level.     

Rapid assessment of butterfly diversity in a montane landscape

We present the results of a rapid assessment of butterfly diversity in the 754 ha Beaver Meadows study area in Rocky Mountain National Park, Larimer County, Colorado. We measured butterfly species richness and relative abundance as part of a landscape-scale investigation of diversity patterns involving several groups of organisms. A stratified random sampling design was used to include replication in both rare and common vegetation types. We recorded 49 butterfly species from the twenty-four 0.1 ha plots that were sampled four times during June, July, and August 1996. Butterfly species richness, diversity, and uniqueness were highest in quaking aspen (Populus tremuloides Michaux) groves and wet meadows, which occupy only a small proportion of the studied landscape. This result supports the suggestion that aspen areas represent hotspots of biological diversity in this montane landscape. Patterns of butterfly species richness were positively correlated with total vascular plant species richness (r = 0.69; P < 0.001), and native plant species richness (r = 0.64; P < 0.001). However, exotic plant species richness (r = 0.70; P < 0.001) and the cover of exotic plant species (r = 0.70; P < 0.001) were the best predictors of butterfly species richness.     

Scale-dependent relationships between the spatial distribution of a limiting resource and plant species diversity in an African grassland ecosystem

One cornerstone of ecological theory is that nutrient availability limits the number of species that can inhabit a community. However, the relationship between the spatial distribution of limiting nutrients and species diversity is not well established because there is no single scale appropriate for measuring variation in resource distribution. Instead, the correct scale for analyzing resource variation depends on the range of species sizes within the community. To quantify the relationship between nutrient distribution and plant species diversity, we measured NO₃^- distribution and plant species diversity in 16 paired, modified Whittaker grassland plots in Serengeti National Park, Tanzania. Semivariograms were used to quantify the spatial structure of NO₃^- from scales of 0.4–26 m. Plant species diversity (Shannon-Weiner diversity index; H ) was quantified in 1-m² plots, while plant species richness was measured at multiple spatial scales between 1 and 1,000 m². Small-scale variation in NO₃^- (<0.4 m) was positively correlated with 1-m² H , while 1,000-m² species richness was a log-normal function of average NO₃^- patch size. Nine of the 16 grassland plots had a fractal (self-similar across scales) NO₃^- spatial distribution; of the nine fractal plots, five were adjacent to plots that had a non-fractal distribution of NO₃^-. This finding offered the unique opportunity to test predictions of Ritchie and Olff (1999): when the spatial distribution of limiting resources is fractal, communities should display a left-skewed log-size distribution and a log-normal relationship between net primary production and species richness. These predictions were supported by comparisons of plant size distributions and biomass-richness relationships in paired plots, one with a fractal and one with a non-fractal distribution of NO₃^-. In addition, fractal plots had greater large-scale richness than paired non-fractal plots (1,0–1000 m²), but neither species diversity (H ) nor richness was significantly different at small scales (1 m²). This result is most likely explained by differences in the scale of resource variation among plots: fractal and non-fractal plots had equivalent NO₃^- variation at small scales but differed in NO₃^- variation at large scales (as measured by the fractal dimension). We propose that small-scale variation in NO₃^- is largely due to the direct effects of plants on soil, while patterns of species richness at large scales is controlled by the patch size and fractal dimension of NO₃^- in the landscape. This study provides an important empirical step in understanding the relationship between the spatial distribution of resources and patterns of species diversity across multiple spatial scales.     

Relationships between landscape patterns and species richness of trees,shrubs and vines in a tropical forest

The present study aims to identify and characterize the relationships among landscape structure and plant diversity in a tropical landscape forest in Quintana Roo, Mexico. Total species richness as well as that of trees, shrubs and vines species were identified from 141 sampling quadrats (16,543 individuals sampled). Based on vegetation classes obtained from multi-spectral satellite image classification, I constructed plant diversity maps of the landscape under study using stratified kriging. I calculated the mean number of species in individual patches as the average values of kriging estimates inside of each patch. I then explored the relationships between landscape pattern metrics and the species richness of trees, shrubs and vines, as well as all groups combined using regression analysis. I employed Akaike Information Criterion (AIC) to select a set of candidate models. Based on akaike weights, I calculated model-averaged parameters. Results show that plant diversity of the patches depends on both the quality of the surrounding habitats and the proximity of surrounding patches (i.e., patch isolation).