Bats in a fragmented landscape: Species composition, diversity and habitat interactions in savannas of Santarém, Central Amazonia, Brazil

Species response to forest fragmentation may strongly vary according to ecological requirements, shape, spatial configuration and connectivity of fragments, and the structure of the surrounding matrix. Bats are natural candidates for studies on forest fragmentation. However, the conclusions of such studies are often contradictory. We present the results of a study on the effects of forest fragmentation on bat communities in Alter do Chão, Santarém area, in Central Amazonia, Brazil, an area composed by forests and fragments surrounded by savanna-like vegetation. We compared the species composition between habitats, tested the effect of size, shape and density of trees of forested areas on the presence species and their relative frequency of captures, and investigated the savannas as an ecological barrier for the dispersion of bats. With an effort of 5678 mistnet-hours, we captured 3740 bats (64 species). Multidimensional Scaling indicated no strong separation between the habitats sampled, however, savanna sites were grouped distinctly of fragments and forest sites. Multiple linear regressions indicated no significant correlation between the number of bat species recorded and the size, shape or tree density in forest sites and fragments. There was a significant correlation between the number of captures and the variables tested, explained by the shape of the sites, but not by size or tree density. In general, sites with bigger shape indices had fewer captures. Ten of the 20 most captured species showed no significant difference between the three habitats. The bat communities in Alter do Chão were not strongly affected by forest fragmentation, and the savannas did not appear to act as an ecological barrier to bats.     

The occurrence of primary burrowing crayfish in terrestrial habitat

A researcher’s perception of a target species’ landscape strongly influences the design of habitat studies conducted at broad spatial scales. Consequently, researcher-dependent perceptions may misguide conservation efforts. Although the life histories of some crayfish (i.e., primary burrowers) are centered on a fossorial existence independent of surface water, all North American crayfish are viewed in an aquatic context. This paradigm restricts the range of habitats that are typically sampled and managed for crayfish conservation. This study used presence/absence of the primary burrower Distocambarus crockeri at 137 locations within the Long Cane Ranger District of the Sumter National Forest, South Carolina, USA, to model the habitat association of the species across a GIS-based landscape. Logistic regression indicated that D. crockeri presence was most strongly associated with a terrestrial habitat defined by a set of morphologically similar soils located along ridge tops. Furthermore, the species was negatively associated with aquatic habitats such as streams and floodplains. The results indicate that D. crockeri is a terrestrial habitat specialist and should be modeled and managed at the landscape as a terrestrial organism. When viewed as a subset of the total United States cambarid fauna, primary burrowers are disproportionately imperiled. Primary burrowers comprise only 15% of the total crayfish fauna, while they account for 32% of those crayfish ranked critically imperiled. Habitat loss and an aquatic bias that restricted sampling to aquatic and semi-aquatic habitats might explain the group’s disproportionate imperilment.     

Identifying, understanding, and describing spatial processes in agricultural landscapes — four case studies

To evaluate the quality of the ecosystem and for making resources and land management decisions landscapes have to be assessed quantitatively. For a better understanding of landscape processes and their characterization, the analysis of the inherent variability is a major factor. Four case studies in which problems associated with landscape analysis are discussed. Spatial processes remain a main focus, as their analysis provides information on the relation between relevant state variables in agricultural landscapes. Variogram analysis showed that mineral soil nitrogen (N_min) sampled in a field at different scales, domains, and times is an instationary spatial process. Spatial association of grain yield, soil index and remotely sensed vegetation index may not be identifiable from kriged contour maps as local coincidence may be obscured behind classified areas. Crop yield in subsequent years and remotely sensed information are not related if a unique response is assumed. An alternative data stratification procedure is described here for the identification of different response functions in agricultural ecosystems. Processes of crop yield and underlying variables are described in autoregressive state-space models. This technique incorporates both deterministic and stochastic relations between different variables and is based on relative changes in space.     

Assessing physical surrogates for biodiversity: Do tributary and stream type classifications reflect macroinvertebrate assemblage diversity in running waters?

Landscape classifications are increasingly being used in conservation planning and biodiversity management, although there is a dearth of studies actually showing concordant patterns between such classifications and biodiversity. We studied the utility of tributary and stream type classifications in accounting for the variability of invertebrate biodiversity in a boreal drainage system. We found that only weak, although significant, differences existed between the studied three tributaries and four stream types in macroinvertebrate assemblage structure, species distributions, and taxonomic richness. Further, the classification strengths, calculated as mean within-group-similarity minus mean between-group-similarity of assemblage structure, were rather low, suggesting that the a priori physical classifications did not effectively describe variability in macroinvertebrate assemblage structure. The low classification strengths likely resulted from the facts that: (i) most stream macroinvertebrate taxa show individualistic responses to environmental gradients; (ii) many taxa occur either across all stream types; or (iii) only sporadically in a given stream type; and (iv) only a few species show high fidelity to a given stream type. However, the significance of the differences in macroinvertebrate assemblage structure and taxonomic richness, as well as a bunch of effective indicator species for different stream types, suggest that such classifications could be used as a preliminary scheme for the conservation planning of running waters. This reasoning is also supported by the evidence from other studies that have found stream size and the distance to upstream lakes to shape considerably the biodiversity of various groups of stream organisms, although no single organism group is likely to show a perfect match with any classification scheme.     

Body size, niche breadth, and ecologically scaled responses to habitat fragmentation: mammalian predators in an agricultural landscape

The ability to make a priori assessments of a species' response to fragmentation, based on its distribution in the landscape, would serve as a valuable conservation and management tool. During 1997-1999, we monitored 717 scent stations to examine seasonal use of forest patches, corridors, and crop fields by coyotes (Canis latrans), domestic cats (Felis catus), foxes (Vulpes vulpes and Urocyon cinereoargenteus), raccoons (Procyon lotor), striped skunks (Mephitis mephitis), opossums (Didelphis virginiana), and long-tailed weasels (Mustela frenata). For each species we developed landscape-based ecologically scaled landscape indices (ELSI), and we modeled species spatial distribution across three spatial scales (landscape-level, element-level, and local habitat-level). Our results suggest that these predators view landscape fragmentation at different spatial scales and demonstrate strong interspecific differences in their response to elements of the landscape. All species except coyotes and domestic cats avoided agricultural fields. In general, predator species that were more mobile (i.e. high ESLI for landscape connectivity; coyotes) were characterized by landscape- and element-based logistic models. In contrast, models including local habitat features generally were most appropriate for less mobile or more stenophagous predators (e.g. long-tailed weasels). Our analysis extends the application of the ESLI concept to species assemblages that do not appear to function as metapopulations, and it highlights the importance of examining spatial scale and species-specific responses to habitat fragmentation. We discuss the relevance of these findings for defining ecological landscapes, understanding predator-prey interactions at multiple spatial scales, and conserving predator and prey populations in fragmented landscapes.     

城市园林绿化树种应用检索系统的开发与应用

当前,城市发展建设中对园林绿化树种重视程度和需求量增加,迅速准确地在我国众多的植物树种中,选择适宜于特定城市的园林绿化树种,成为城市园林绿化的首要问题。针对这一问题,采用PowerBuilder9.0开发工具设计开发城市园林绿化树种应用系统。本系统不仅具备能够对已收录的大量的植物树种中特定科、属、种植物的特性进行查询,更重要的是可以根据绿化城市的实际需要灵活设置绿化评价指标体系,从而实现对特定树种的绿化评价与检索功能。本系统的开发与应用可以为特定城市的园林绿化提供快速的树种选择方案,为城市园林绿化规划的制定提供科学的导向和决策的依据。     

Sex and seasonal differences in the spatial terrestrial distribution of gray treefrog (Hyla versicolor) populations

Fragmentation of terrestrial landscapes has exacerbated the need to understand the spatial requirements of organisms, especially those that undergo seasonal migrations, such as pond-breeding amphibians. Pond-breeding amphibians spend much of their lives in terrestrial habitat at some distance from aquatic breeding sites. The terrestrial habitat required by a particular individual encompasses the area adjacent to a breeding pond that is used for activities such as foraging or overwintering, as well as the expanses of habitat through which it moves. To elucidate amphibian spatial habitat requirements, we monitored gray treefrog (Hyla versicolor) movements through terrestrial habitat adjacent to breeding ponds using radiotelemetry and mark–recapture along transects of artificial refugia. Results indicate that gray treefrogs frequently make migrations between foraging grounds, overwintering sites, and breeding ponds of 200 m or more, with a maximum-recorded movement distance of 330 m. Additionally, females travel farther than males for reasons independent of body size, and the distribution of males during the breeding season is biased towards breeding ponds relative to the non-breeding season. The data illustrate the importance of habitat directly adjacent to breeding sites for males, and indicate that habitat loss resulting in small patches may have a greater negative impact on females than males, and consequently may have disproportionately large effects on population persistence. These results emphasize that effective management of amphibian breeding locations via protection of both aquatic and adjacent upland terrestrial resources likely requires detailed information regarding variation in movements between the sexes and among seasonal activity periods.     

Core terrestrial habitat for conservation of local populations of salamanders and wood frogs in agricultural landscapes

Pond-breeding amphibians require aquatic and terrestrial habitats to complete their lifecycles, and preservation of both habitats is necessary for maintaining local populations. Current wetland regulations focus primarily on aquatic habitats, and criteria to define critical upland habitats and regulations to protect them are often ambiguous or lacking. We examined the association between the presence of seven pond-breeding amphibian species and the landscape composition surrounding 54 wetlands located within the Till Plains and the Glaciated Plateau ecoregions of Ohio, USA. We quantified landscape composition within 200 m of the wetland (“core terrestrial zone”) and the area extending from 200 m to 1 km from the wetland (“broader landscape context zone”). We constructed binary logistic regression models for each species, and evaluated them using Akaike Information Criterion. Presence of spotted salamanders (Ambystoma maculatum), Jefferson's salamander complex (A. jeffersonianum) and smallmouth salamanders (A. texanum) was positively associated with the amount of forest within the core zone. Presence of wood frogs (Rana sylvatica) was positively associated with the amount of forest within the core zone and the amount of forest within the broader landscape context zone. Presence of tiger salamanders (A. tigrinum tigrinum) was negatively associated with the cumulative length of paved roads within 1 km of the site, and presence of red-spotted newts (Notophthalmus v. viridescens) was negatively associated with the average linear distance to the five nearest wetlands. Overall salamander diversity was positively associated with the amount of forest within the core zone, and negatively associated with the presence of predatory fish and cumulative length of paved roads within 1 km of the site. Our results confirm the strong association between the structure of surrounding upland areas and amphibian diversity at breeding ponds, and stress the importance of preserving core terrestrial habitat around wetlands for maintaining amphibian diversity.     

谈园林植物病虫害防治

随着社会经济的发展,园林绿化工作取得了前所未有的成绩,园林植物的生态效益、经济效益、观赏效益日益凸现。与此同时,园林植物病虫害的发生也出现了复杂化、危险化的趋势,对绿地和风景区危害较大。病虫害常常导致园林植物生长衰弱和死亡,影响植物的生长、发育、繁殖及其观赏价值,甚至引起整株死亡,使绿化树种、风景林等林木大片衰败或死亡,从而造成重大的经济损失。在园林生态里,由于人类、植物、有害生物、环境条件和天敌等各组分之间存在着相当复杂的关系,所以其中任何一因子的变动,都会直接或间接地影响整个的城市园林生态系统。那么,在防治上要从生态学观点出发,在管理上创造不利于病虫害发生的条件,减少或不用化学农药,保护天敌,提高自然的控制能力,保持园林生态的稳定和可持续性发展。     

浅析北京园林之意境

以北京园林为例,浅析北京园林意境的形成,阐述传统北京园林的意境营造和文脉传承.指出园林中空间处理和文脉传承的重要性,并对指导北方现代园林的建设、改善目前千城一面的现状提出建议.