Responses of mammals to habitat edges: an overview

Life generates discontinuites (boundaries) in the distribution of matter and energy. One class of these constitutes the edges between habitat-types; these are fundamental structures in landscape functioning, and hence are of central importance in conservation biology. The symposium on which this series of papers is based focused on the responses of mammals to habitat edges. A diversity of views are represented, and a variety of edge related behaviors illustrated. A survey of general ecology texts dating back to 1933 demonstrates a decline of interest in ecotones and edge effects extending into the 1980's but showing a resurgence of interest in the 1990's. Habitat edges are defined operationally with respect to particular focal species leading to a number of important corollary features. The variety of phenomena subsumed under edge effects is emphasized, and an initial attempt at classification is proposed based primarily on the presence or absence of emergent properties in edge response behaviors (matrix vs. ecotonal effects). This scheme provides for clear null hypotheses needed to distinguish the two types, enlightens mechanistic explanations of edge effects, and encourages predictions about the results of untested management schemes or other novel situations. The use and design of landscape corridors are tied to edge related behaviors. A functional and general definition of corridors is urged, so that their effectiveness can be judged with respect to specified attributes rather than to a general collection of things that might be termed corridors. Linear habitat patches are specifically excluded from the definition. Studies on small mammals have contributed to our understanding of the potential role of corridors in metapopulation dynamics. Fine versus coarse grained perceptions of environment by different species will generate ecotonal edge effects such as spillover predation. In general, the effects on landscape processes of various species operating on different spatial scales seems a fruitful direction for future research.     

Movements of small mammals in the heterogeneous landscape

Distances and directions of Apodemus agrarius and Clethrionomus glareolus movements were studied using snap traps and colored bait. The longest distances traversed exceeded 1500 m. Some directions of movement were significantly more common. High variability in the number of captures along traplines suggests distinct movement routes. Small mammals appear to base their movement on the landscape and not on individual biotopes.     

Responses of a small mammal community to heterogeneity along forest-old-field edges

Despite the importance of edges effects in ecological systems, the causes and consequences of animal responses to habitat edges are largely unknown. We used three years of live-trapping and measures of the plant community around trap stations to explore the responses of white-footed mice (Peromyscus leucopus), meadow voles (Microtus pennsylvanicus), and short-tailed shrews (Blarina brevicauda) to forest-field edges in upstate New York. We found that capture probabilities of voles were highest in grass- and forb-dominated micro-habitats and in old-field zones distant from the forest edge. In contrast, capture probabilities of white-footed mice were highest in shrub-dominated microhabitats and in zones near the forest edge. Short-tailed shrews did not show strong micro- or macrohabitat associations. The responses by voles, the competitive dominant in our system, to variation along forest-field edges were more consistent across years than were those of the competitively inferior, white-footed mouse. Mice were less likely to use the old-field interiors when vole density was high than when it was low, suggesting competitive displacement of mice by voles. Finally, we found good agreement between the spatial activity patterns of mice and voles in old-fields and their impacts on patterns of survival of tree seeds and seedlings in concurrent studies. These results suggest that a dynamic interaction exists between the plant and animal communities along forest edges.     

Plants,small mammals,and the hierarchical landscape classifications of Patagonia

Assemblages of plants were studied at 14 sites in northern Patagonia corresponding to localities at which we (Monjeau et al. 1997) earlier studied the relationship between small mammal assemblages and landscape classifications. This allowed us to test predictions that both plants and small mammals correspond to the more inclusive hierarchical landscape divisions but that plants track better than small mammals the less inclusive divisions. Species presence or absence of plants at each locality was used in a series of multivariate analyses and compared by correlation analysis with those generated from small mammal species data. Assemblages of both plants and small mammals corresponded to the upper divisions, which are based on climatic and geomorphological features, but small mammal assemblages did not correspond to the lower divisions of the landscape classifications. Three factors are considered as explanations for the observed differences between plants and small mammals: a) small mammal habitat is determined more by plant growth form than by plant species; b) trophic level differences between the two groups; and c) species pool size affects the resolution of microhabitat correspondence. Our data indicate that both plant assemblages and small mammal assemblages respond to climatic and geomorphological features, which is in contrast to the paradigm that mammal assemblages simply follow plant assemblages. We also attempted to reconcile classification systems in Patagonia by proposing a nomenclatural system based on a hierarchical classification. In the system proposed, ecoregion is the lowest division small mammal assemblages can recognize in Patagonia. Finally, we conclude that the hierarchical nature of landscapes based on a holistic view of environments reflects real entities that are not just the perceptions of landscape ecologists.     

Components of small urban parks that predict the possibility for restoration

In densifying cities, small green spaces such as pocket parks are likely to become more important as settings for restoration. Well-designed small parks may serve restoration well, but earlier research on restorative environments does not provide detailed information about the specific components of the physical environment that support restoration. In this study we assessed the extent to which hardscape, grass, lower ground vegetation, flowering plants, bushes, trees, water, and size predicted the judged possibility for restoration in small urban green spaces. We took individual parks as the units of analysis. The parks were sampled from Scandinavian cities, and each park was represented by a single photo. Each photo was quantified in terms of the different objective park components and also rated on psychological variables related to restoration. The ratings on the psychological variables being away, fascination, likelihood of restoration, and preference were provided by groups of people familiar with such parks. The variables most predictive of the likelihood of restoration were the percentage of ground surface covered by grass, the amount of trees and bushes visible from the given viewing point, and apparent park size. Formal mediation analyses indicated distinctive patterns of full and partial mediation of the relations between environmental components and restoration likelihood by being away and fascination. Our results provide guidance for the design of small yet restorative urban parks.     

Habitat corridors and the conservation of small mammals in a fragmented forest environment

At Naringal in south-western Victoria, Australia, clearing of the original forest environment has created an agricultural landscape dominated by grazed pastures of introduced grasses. Remnant forest vegetation is re-stricted to small patches of less than 100 ha in size, that are loosely linked by narrow forested strips along road reserves and creeks. Six native and two introduced species of small terrestrial mammal (< 2 kg) occur within this environment. The native mammals, being dependent upon forest vegetation, were less tolerant to forest fragmentation than were the introduced species that also persist in farmland and farm buildings. The native mammals displayed an increasing frequency of occurrence in successively larger size-classes of forest patches. Those species with the greatest body-weight were the most vulnerable to habitat loss. All species of small mammal occurred in narrow habitat corridors of forest vegetation on roadsides. The resident status, seasonal variation in relative abundance, patterns of reproduction, and movements of each species were monitored in two habitat corridors during a 25-month trapping study. The corridors were found to facilitate continuity between otherwise-isolated populations of small mammals in this locality in two ways: firstly, by providing a pathway for the dispersal of single animals between patches; and secondly, by enabling gene flow through populations resident within the corridors. The small size of forest remnants at Naringal, and the vulnerability of species with low population sizes, emphasize the importance of preserving a mosaic of numerous habitat patches that together will support regional populations of sufficient size for longer-term persistence. The continuity between remnant habitats that is provided by a network of habitat corridors is an essential, and critical, component of this conservation strategy.     

Urban fruit orchards: Biodiversity and management restoration effects in the context of land use

Urban areas have increased greatly in recent decades, which has resulted in habitat loss. However, the promotion of urban green spaces could have a profound effect on biodiversity. Traditional fruit orchards are an important land-use type with the potential to host myriad organisms. Our goal was to determine the most important factors that influence orchard biodiversity in the million city of Prague (the capital of the Czech Republic). We used a multitaxon approach to evaluate the effect of orchard restoration in a landscape context. Restoration had a positive impact on species diversity, specifically, the diversity of orthopterans and butterflies. Moreover, landscape context determined the biodiversity of orthopterans, butterflies, and birds but not that of lichens. Our study underlines the importance of both the internal and external structures of traditional fruit orchards for species richness and composition. The results of our study support the restoration of traditional fruit orchards as a suitable management practice for promoting city biodiversity. Furthermore, orchard restoration can improve the attractiveness of suburban areas. Such areas often lack sufficient urban greening. Thus, restoration in these areas can also increase future recreational value.     

Matrix is important for mammals in landscapes with small amounts of native forest habitat

Acknowledgment that the matrix matters in conserving wildlife in human-modified landscapes is increasing. However, the complex interactions of habitat loss, habitat fragmentation, habitat condition and land use have confounded attempts to disentangle the relative importance of properties of the landscape mosaic, including the matrix. To this end, we controlled for the amount of remnant forest habitat and the level of fragmentation to examine mammal species richness in human-modified landscapes of varying levels of matrix development intensity and patch attributes. We postulated seven alternative models of various patch habitat, landscape and matrix influences on mammal species richness and then tested these models using generalized linear mixed-effects models within an information theoretic framework. Matrix attributes were the most important determinants of terrestrial mammal species richness; matrix development intensity had a strong negative effect and vegetation structural complexity of the matrix had a strong positive effect. Distance to the nearest remnant forest habitat was relatively unimportant. Matrix habitat attributes are potentially a more important indicator of isolation of remnant forest patches than measures of distance to the nearest patch. We conclude that a structurally complex matrix within a human-modified landscape can provide supplementary habitat resources and increase the probability of movement across the landscape, thereby increasing mammal species richness in modified landscapes.     

Corridor use by small mammals: field measurement for three experimental types of Peromyscus leucopus

Eighteen mice of each of 3 types were radio-tagged and released at 6 standard points in farmland fencerows. Mice were residents (trapped on site) or translocated from distant forest or from distant corn fields. Of total (net) distance moved, most was in fencerows; 77% for residents, 83% for mice translocated from cropland and 92% for mice translocated from forest. Structurally complex fencerows were preferred significantly over intermediate or simple structures by all types of mice. Time spent in movement was not a linear function of distance moved and averaged from 12.5 to 16.5% of total available activity time. Total distance moved in 2 nights averaged 287 to 422 m and area explored averaged 0.67 to 1.15 ha and ranged to 11.0 ha; both exceed literature values for this species in forest. This enlarged scale of landscape use illustrates the potential importance of landscape-specific behaviour. The measurement of rate of corridor use also is discussed.     

Effects of agroecosystem landscape complexity on small mammals: a multi-species approach at different spatial scales

Landscape Ecology - The effect of landscape complexity on biodiversity is an important topic in landscape ecology, and spatial scale is key to understand true species-landscape relationships. We...     

From landscape ecology to forest landscape restoration

Landscape Ecology - Forest landscape restoration (FLR) was first defined in 2000 and has emerged from several disciplines, including conservation biology and landscape ecology. As it has gained in...     

Multi-scaled habitat considerations for conserving urban biodiversity: native reptiles and small mammals in Brisbane,Australia

The rapid expansion of the world’s urban population is a major driver of contemporary landscape change and ecosystem modification. Urbanisation destroys, degrades and fragments native ecosystems, replacing them with a heterogeneous matrix of urban development, parks, roads, and isolated remnant fragments of varying size and quality. This presents a major challenge for biodiversity conservation within urban areas. To make spatially explicit decisions about urban biodiversity conservation actions, urban planners and managers need to be able to separate the relative influence of landscape composition and configuration from patch and local (site)-scale variables for a range of fauna species. We address this problem using a hierarchical landscape approach for native, terrestrial reptiles and small mammals living in a fragmented semi-urban landscape of Brisbane, Australia. Generalised linear modelling and hierarchical partitioning analysis were applied to quantify the relative influence of landscape composition and configuration, patch size and shape, and local habitat composition and structure on the species’ richness of mammal and reptile assemblages. Landscape structure (composition and configuration) and local-scale habitat structure variables were found to be most important for influencing reptile and mammal assemblages, although the relative importance of specific variables differed between reptile and mammal assemblages. These findings highlight the importance of considering landscape composition and configuration in addition to local habitat elements when planning and/or managing for the conservation of native, terrestrial fauna diversity in urban landscapes.     

A consilience-driven approach to land use history in relation to reconstructing forest land use legacies

Landscape Ecology - The importance of societal factors in shaping forest area, structure and composition through economic activity, policy, governance, and population changes is frequently...     

对开蕨对遮荫处理的响应

研究了全光和遮光30%、50%、70%、90%处理对对开蕨生长及光合生理特性的影响。结果表明:随着遮光强度的增大,对开蕨叶片面积、单位叶面积鲜质量、叶绿素含量、叶片含水量增加,可溶性糖含量、可溶性蛋白含量下降;净光合速率日变化呈双峰曲线,有光合"午休"现象;日平均净光合速率以遮光50%～70%处理为最佳;光补偿点逐渐降低;光饱和点在遮光50%处理下最高,遮光70%和90%处理下较低。综合考虑,对开蕨适宜的光环境为遮光50%～70%。     

Responses of glasshouse roses to light conditions

Effects of light intensity and duration on the vegetative and reproductive characters of the rose cultivar ‘Baccara’ were studied for a year. Production of unlighted ‘Baccara’ in S.W. England reflected the solar energy curve; the highest flower yield followed the vegetative phase receiving the most natural light. Lighting improved flower yield, decreased blind shoots and hastened flowering, in proportion to the quantity of light received, especially during periods of limited natural light. Intensity was more effective than duration. Bottom breaks and axillary shoot development were stimulated by lighting, the latter being associated with higher yields. Lighting the plants in the morning and evening increased yield more than giving the same quantity of light during the day.High pressure sodium lamps (SON/T) were effective as supplementary light to glasshouse roses, especially when higher intensities were required. Lighting with sodium lamps significantly increased flower yield and decreased the number of blind shoots. Some characteristics studied were highly correlated in all experiments.     

Using traffic flow theory to model traffic mortality in mammals

Traffic has a considerable effect on population and community dynamics through the disruption and fragmentation of habitat and traffic mortality. This paper deals with a systematic way to acquire knowledge about the probabilities of successful road crossing by mammals and what characteristics affect this traversability. We derive a model from traffic flow theory to estimate traffic mortality in mammals related to relevant road, traffic and species characteristics. The probability of successful road crossing is determined by the pavement width of the road, traffic volume, traversing speed of the mammals and their body length. We include the traversability model in a simple two-patch population model to explore the effects of these road, traffic and species characteristics on population dynamics. Analysis of the models show that, for our parameter ranges, traffic volume and traversing speed have the largest effect on traffic mortality. The population size is especially negatively affected when roads have to be crossed during the daily movements. These predictions could be useful to determine the expected effectiveness of mitigating measures relative to the current situation. Mitigating measures might alter the road and traffic characteristics. The effects of these changes on traffic mortality and population dynamics could be analysed by calculating the number of traffic victims before and after the mitigating measures. This revised version was published online in July 2006 with corrections to the Cover Date.     

Using traffic flow theory to model traffic mortality in mammals

Traffic has a considerable effect on population and community dynamics through the disruption and fragmentation of habitat and traffic mortality. This paper deals with a systematic way to acquire knowledge about the probabilities of successful road crossing by mammals and what characteristics affect this traversability. We derive a model from traffic flow theory to estimate traffic mortality in mammals related to relevant road, traffic and species characteristics. The probability of successful road crossing is determined by the pavement width of the road, traffic volume, traversing speed of the mammals and their body length. We include the traversability model in a simple two-patch population model to explore the effects of these road, traffic and species characteristics on population dynamics. Analysis of the models show that, for our parameter ranges, traffic volume and traversing speed have the largest effect on traffic mortality. The population size is especially negatively affected when roads have to be crossed during the daily movements. These predictions could be useful to determine the expected effectiveness of mitigating measures relative to the current situation. Mitigating measures might alter the road and traffic characteristics. The effects of these changes on traffic mortality and population dynamics could be analysed by calculating the number of traffic victims before and after the mitigating measures. This revised version was published online in July 2006 with corrections to the Cover Date.     

Responses of blackcurrant bushes to post-harvest moisture stress

Potted blackcurrant plants subjected to moisture stress following harvest produced 50% less total fruit yield in the following season than plants which received regular irrigation. The factors which contributed to this effect were a reduction in the numbers of productive buds, flowers per bud and fruit set. An increase in seed number per fruit in response to the stress suggested that reserve carbohydrates accumulated during the autumn may have been the controlling factor in fruit set.Bud-burst in the stressed plants was both early and uneven, radial growth was reduced, and there was no evidence of starch accumulation at the onset of dormancy.All plants received the same irrigation treatment in the spring following treatment, and there was no significant difference in fruit size except for a few positions at the distal end of the strig. Fruit on stressed plants in this case were the smallest.     

The effect of roads on edge permeability and movement patterns for small mammals: a case study with Montane Akodont

Context

Increased edge density is among the main negative effects of habitat loss and fragmentation. Roads are linear infrastructures that may promote barrier effects due to disturbance and mortality effects. We hypothesized that edges of habitat patches bordered by roads are less permeable than roadless edges.

Objectives

We tested whether edge permeability and avoidance are influenced by the presence of paved and dirt roads bordering habitat patches, relatively to roadless edges.

Methods

We translocated 55 montane akodonts (Akodon montensis) from the interior of vegetation remnants to their edges, and tracked fine-scale movements using spool-and-line devices. Edges were bordered by dirt roads (n = 12 mice), paved roads (n = 21) or were not bordered by roads (n = 22). We assessed edge permeability by comparing the number of tracks with crossings, and by comparing the empirical data to simulated correlated random walks. We also assessed edge avoidance by comparing the net direction travelled and net displacement from edge.

Results

No edge crossings were recorded in roaded edges, whereas 36% of tracks in roadless edges crossed the edge at least once. Simulations indicated a significantly lower permeability of roaded edges, while the observed number of crossings in roadless edges was within the expected range. We found no evidence of higher avoidance of roaded edges, as both net direction travelled and displacement were similar across edge types.

Conclusions

Roads decreased edge permeability for the montane akodont. This is likely to increase population isolation among vegetation remnants by reducing the structural connectivity in the already fragmented landscape.

     

中国石蒜生长特性及高量施肥研究

研究了高用量的尿素和氮磷钾(N-P-K)复合肥双因素施肥对中国石蒜(Lycorischinensis)的当季和次年叶生长量及鳞茎生物量的影响,并且对叶量进行了主观评价。结果表明:高用量的尿素对中国石蒜的生长产生负面影响;N-P-K复合肥对中国石蒜生长未达到显著性影响水平;叶的数量与鳞茎生物量呈线性正相关;主观评价定性结果与鳞茎生物量结果类似。