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1.
Conservation and enhancement of ecological connectivity is widely recognized as one of the key objectives of forest landscape management. However, practical difficulties still exist due to the lack of pragmatic and operational methodologies that can be efficiently applied for these purposes within the scope of a forest management plan. Here we present the novel integration of two recent approaches for analyzing forest structural connectivity that offers considerable synergies and potential relevant benefits for forest planning at a variety of scales. We combine the morphological analysis of forest spatial patterns with recent indices for the analysis of landscape network connectivity based on the concept of measuring habitat availability (reachability) at the landscape scale. The combination of these approaches in a single integrated workflow embraces from (1) the diagnosis and characterization at the pixel level of the forest spatial patterns and their individual constituents, which are mainly the core habitat areas and the structural connectors (bridges) between them, to (2) the assessment of their individual importance to uphold ecological fluxes as irreplaceable providers of structural connectivity. We present and show different analytical possibilities within the integrated workflow from where the manager can choose depending on the planning targets and on the characteristics of the ecological processes of interest. We illustrate the application of the combined approach in two forested areas in Central Spain with different scales and management contexts, in which the structural connectivity between forest habitat areas needs to be sustained. Our assessment was able to discriminate and highlight a concise subset of cores and bridges that concentrated most of the contribution to the overall connectivity and functioning of the forest habitat network. This provides clear guidelines on where the conservation management efforts should be targeted, allowing for many alternative areas where the rest of the management objectives and activities can be accommodated as required by the multifunctionality of forest resources. The proposed integrated approach can equally serve to identify (a) those forest areas that play a crucial role to sustain ecological fluxes that are to be promoted by management, such as the dispersal of native biota or (b) those sites where the spread of wildfires or invasive species can be halted more effectively. The potential of the proposed methodology to inform and guide forestry decisions is reinforced by the availability of the required analytical tools (Guidos and Conefor Sensinode) as freeware software packages.  相似文献   

2.
Connectivity is a key concern in natural resource planning. Many studies have focused on the development of methods, tools and indices for the assessment of both components of connectivity: structural and functional. In particular, approaches based on graph theory principles have been recently proposed and are being increasingly applied to guide landscape connectivity conservation. However, forest planners and managers still need effective and operational methodologies to detect those landscapes where connectivity should be treated as a particularly critical conservation concern. In addition, in the Mediterranean, as in other parts of the world, socioeconomic changes in the last decades have driven the abandonment of many formerly cultivated lands. This poses both a challenge and an opportunity for managers intending to restore ecological connectivity in forested areas. In this context, setting adequate priorities for the reforestation of agricultural lands is of outmost importance. Here we show how a two-stage hierarchical methodology based on network analysis can be used to meet these needs. In particular, we apply a graph metric based on the measurement of habitat availability at the landscape scale (the Integral Index of Connectivity) to two Mediterranean forest districts in Spain with different management objectives and environmental heterogeneity. First, we identify those landscapes where efforts to improve forest connectivity should be concentrated. In a second stage, we prioritize within those landscapes the individual patches of agricultural lands that, being available for a potential reforestation program, would contribute most to uphold connectivity and ecological flows at wide spatial scales. We show how the extent of the agricultural patches is not strictly related to the contribution to connectivity they would provide if reforested, and how the results of such analysis vary with species traits (dispersal capabilities). We discuss the suitability of the proposed approach for forest landscape planning purposes and conclude that it can provide a useful diagnosis and helpful guidelines for the development of efficient reforestation programs that might be applied in a variety of situations for improving the ecological coherence of forest landscapes.  相似文献   

3.
Large-scale information on habitat suitability is indispensable for planning management actions to further endangered species with large-spatial requirements. So far, remote sensing based habitat variables mostly included environmental and land cover data derived from passive sensors, but lacked information on vegetation structure. This is a serious constraint for the management of endangered species with specific structural requirements. Light detection and ranging (LiDAR), in contrast to passive remote sensing techniques, may bridge this gap in structural information at the landscape scale. We investigated the potential of LiDAR data to quantify habitat suitability for capercaillie (Tetrao urogallus), an endangered forest grouse in Central Europe, in a forest reserve of 17.7 km2. We used continuous variables of horizontal and vertical stand structure from first and last pulse LiDAR data and presence–absence information from field work to model habitat suitability with generalized linear models (GLM). The two final habitat suitability models explained the observed presence–absence pattern moderately well (AUC of 0.71 and 0.77) with horizontal structure explaining better than vertical structure. Relative tree canopy cover was the most important variable with intermediate values indicating highest habitat suitability. As such, LiDAR allowed us to translate the results from habitat modeling at the landscape scale to effective management recommendations at the local scale at a level of detail that hitherto was unavailable for large areas. LiDAR thus enabled us to integrate individual habitat preferences at the scale of entire populations and thus offers great potential for effective habitat monitoring and management of endangered species.  相似文献   

4.
Regional conservation planning frequently relies on general assumptions about historical disturbance regimes to inform decisions about landscape restoration, reserve allocations, and landscape management. Spatially explicit simulations of landscape dynamics provide quantitative estimates of landscape structure and allow for the testing of alternative scenarios. We used a landscape fire succession model to estimate the historical range of variability of vegetation and fire in a dry forest landscape (size ca. 7900 km2) where the present-day risk of high severity fire threatens the persistence of older closed canopy forest which may serve as Northern Spotted Owl (Strix occidentalis caurina) habitat. Our results indicated that historically, older forest may have comprised the largest percentage of the landscape (∼35%), followed by early successional forest (∼25%), with about 9% of the landscape in a closed canopy older forest condition. The amount and condition of older forest varied by potential vegetation type and land use allocation type. Vegetation successional stages had fine-grained spatial heterogeneity in patch characteristics, with older forest tending to have the largest patch sizes among the successional stages. Increasing fire severities posed a greater risk to Northern Spotted Owl habitat than increasing fire sizes or frequencies under historical fire regimes. Improved understanding of historical landscape-specific fire and vegetation conditions and their variability can assist forest managers to promote landscape resilience and increases of older forest, in dry forests with restricted amounts of habitat for sensitive species.  相似文献   

5.
Conservation organizations in the northeastern United States (US) recommend forest clearcutting to create shrubland habitat, which is required by many wildlife species with declining populations. The planning of habitat management programs is hampered by a lack of information on the current extent of shrubland habitat and the current rate of forest clearcutting that creates shrubland habitat. We addressed these information gaps by using a combination of automated and manual approaches to determine the extent and spatial configuration of shrubland habitat and recent forest clearcuts. We focused on the state of Rhode Island because (a) it is representative of the northeastern US in terms of the prevalence of private ownership of forests, and the ongoing decline in the populations of many shrubland wildlife species; (b) federal, state and private conservation groups are actively promoting clearcuts to create shrubland habitat; (c) many state-wide GIS databases are available; and (d) the spatial extent of the state made our results both generalizable and politically relevant. Our fine-scale mapping allowed a detailed analysis of shrubland distribution in conjunction with other available GIS layers that facilitates identification of priority areas for habitat management. We found that the extent of upland shrubland in non-coastal areas is decreasing by at least 1.5% annually. Considering the lack of consensus about conservation targets for the amount of shrubland, we propose that conservation organizations attempt to stabilize rather than expand the extent of shrubland habitat. This approach would provide an opportunity to assess whether the current extent of shrubland is sufficient to maintain reduced but stable wildlife populations that require this habitat. We propose a coordinated forest management program with targets for increased forest management on conservation lands. We found that the average patch size of shrubland created by recent clearcuts is large enough for most shrubland bird species, but too small for the New England cottontail (Sylvilagus transitionalis), which has been proposed for threatened and endangered status.  相似文献   

6.
The mountain spruce forests of the Western Carpathians have experienced a dramatic deterioration in the last decades increasing the landscape fragmentation. This considerably affected the Western capercaillie population recently surviving within small habitat patches surrounded by unfavourable habitats. Our study shows that the long-term isolation resulted in genetic differentiation with decreasing trend in allelic richness towards the most adjacent western subpopulations. We evaluated dispersal possibilities within the landscape and identified barriers and the most critical corridors between genetically distinct subpopulations. Landscape genetic analysis confirmed that the isolation by environmental features explains the observed genetic patterns better than straight geographical distance. We highlight the urgent need for an active conservation management in the critical habitats where dispersion might be constrained or “bottlenecked” in order to ensure gene flow within the fragmented capercaillie metapopulation of the Western Carpathian mountain forests.  相似文献   

7.
Numerous studies have explored the influence of forest management on avian communities empirically, but uncertainty about causal relationships between landscape patterns and temporal dynamics of bird communities calls into question how observed historical patterns can be projected into the future, particularly to assess consequences of differing management alternatives. We used the Habplan harvest scheduler to project forest conditions under several management scenarios mapped at 5-year time steps over a 40-year time span. We used empirical models of overall avian richness, richness of selected guilds, and probability of presence for selected species to predict avian community characteristics for each of the mapped landscapes generated for each 5-year time step for each management scenario. We then used time series analyses to quantify relationships between changes in avian community characteristics and management-induced changes to forest landscapes over time. Our models of avian community and species characteristics indicated habitat associations at multiple spatial scales, although landscape-level measures of habitat were generally more important than stand-level measures. Our projections showed overall avian richness, richness of Neotropical migrants, and the presence of Blue-gray Gnatcatchers and Eastern Wood-pewees varied little among management scenarios, corresponding closely to broad, overall landscape changes over time. By contrast, richness of canopy nesters, richness of cavity nesters, richness of scrub-successional associates, and the presence of Common Yellowthroats showed high temporal variability among management scenarios, likely corresponding to short-term, fine-scale changes in the landscape. Predicted temporal variability of both interior-forest and early successional birds was low in the unharvested landscape relative to that in the harvested landscape. Our results also suggested that early successional species can be sensitive to both availability and connectivity of habitat on the landscape. To increase or maintain the avian diversity, our projections indicate that forest managers need to consider landscape-scale configuration of stands, maintaining a spatially heterogeneous distribution of age classes. Our findings suggest which measures of richness or species presence may be appropriate indicators for monitoring effects of forest management on avian communities, depending on management objectives.  相似文献   

8.
Natural disturbances including wildfire, insects and disease are a growing threat to the remaining late successional forests in the Pacific Northwest, USA. These forests are a cornerstone of the region's ecological diversity and provide essential habitat to a number of rare terrestrial and aquatic species including the endangered northern spotted owl (Strix occidentalis caurina). Wildfires in particular have reduced the amount of late successional forests over the past decade, prompting land managers to expand investments in forest management in an attempt to slow losses and mitigate wildfire risk. Much of the emphasis is focused specifically on late successional reserves established under the Northwest Forest Plan to provide habitat for spotted owls. In this paper, we demonstrate a probabilistic risk analysis system for quantifying wildfire threats to spotted owl habitat and comparing the efficacy of fuel treatment scenarios. We used wildfire simulation methods to calculate spatially explicit probabilities of habitat loss for fuel treatment scenarios on a 70,245 ha study area in Central Oregon, USA. We simulated 1000 wildfires with randomly located ignitions and weather conditions that replicated a recent large fire within the study area. A flame length threshold for each spotted owl habitat stand was determined using the forest vegetation simulator and used to predict the proportion of fires that resulted in habitat loss. Wildfire modeling revealed a strong spatial pattern in burn probability created by natural fuel breaks (lakes and lava flows). We observed a non-linear decrease in the probability of habitat loss with increasing treatment area. Fuels treatments on a relatively minor percentage of the forested landscape (20%) resulted in a 44% decrease in the probability of spotted owl habitat loss averaged over all habitat stands. The modeling system advances the application of quantitative and probabilistic risk assessment for habitat and species conservation planning.  相似文献   

9.
At the landscape-level Aerial Photograph Interpretation (API) is one of the oldest and most common tools for mapping forest structure. The variety of attributes available for API classifications can produce 100s of different patch types as a basis for mapping landscape mosaics. However, these maps are often difficult to interpret or use for monitoring the impacts of management and natural disturbance. In this study, we demonstrate an approach for quantifying the landscape forest structure described by API data sets. For this purpose we utilised a forest dataset comprising 1197 field plots and API mapping of crown structural characteristics for 773,280 ha of State Forest in Victoria, Australia. Our approach involved: (i) stratification of the landscape into distinct forest communities; (ii) construction of stand-level structural complexity indices for each forest community; (iii) use of stand-level indices of structural complexity to classify API typing into distinct canopy structural classes; (iv) calculation of the distance from each point within a landscape grid to achieve a full complement of canopy structural classes within each forest community. We term our methodology the distance to structural complement (DiSCo) approach, because it identifies the minimum distance to achieve a full complement of structural units within the landscape. We demonstrate the use of these values in mapping landscape structure and their potential for monitoring and modelling the effects of disturbance at this scale, including impacts on heterogeneity, connectivity, individual faunal species and particular forest communities.  相似文献   

10.
Forest Stewardship Council (FSC) is one of the leading forest certification schemes. While many studies concern political aspects and social outcomes of FSC, little is known about the contribution of certification to biodiversity conservation. In Europe, the Russian Federation and Sweden have the largest areas of FSC-certified forest. We assessed the potential of FSC certification for boreal biodiversity conservation in terms of standard content, and outcomes as habitat area set aside and habitat network functionality. First, we compared the biodiversity conservation indicators at different spatial scales in Swedish and Russian FSC standards. Second, focusing on one large state forest management unit in each country, we compared the areas of formally and voluntarily set aside forests for biodiversity conservation. Third, we evaluated the structural habitat connectivity by applying morphological spatial pattern analysis, and potential functional connectivity by using habitat suitability index modelling for virtual species. The Russian standard included indicators for all spatial scales of biodiversity conservation, from tree and stand to landscape and ecoregions. The Swedish standard focused mainly on stand and tree scales. The area of voluntary set-asides for FSC was similar in Sweden and Russia, while formal protection in the Russian case study was three times higher than in the Swedish one. Swedish set-aside core areas were two orders of magnitude smaller, had much lower structural and potential functional connectivity and were located in a fragmented forestland holding. We conclude that to understand the potential of FSC certification for biodiversity conservation both the standard content, and its implementation on the ground, need to be assessed. We discuss the potential of FSC certification for biodiversity conservation with different levels of ambition. We stress the need for developing rapid assessment tools to evaluate outcomes of FSC for biodiversity conservation on the ground, which could be used by forest managers and FSC-auditors toward adaptive governance and management.  相似文献   

11.
城市生物多样性保护是食物生产、人类健康和城市安全的必要保障,生态安全格局的构建能够维护自然生态平衡、保持生境稳定性和提高景观连通度,是生物多样性保护的重要空间途径。以吕梁市为例,采用形态学空间格局分析法和景观连通性指数法定量评估生态斑块重要性,辨别生态源地,利用最小累积阻力模型提取生态廊道和战略点,构建市域生物多样性保护的生态安全格局。结果表明:景观格局中核心区、桥接区、孤岛为林地和水域要素主要构成;沿吕梁山脉带状分布的生态源地景观连通性较大,西部生态源地面积较小且斑块重要性相对较低;"两纵,多横"的生态廊道布局和战略点布设,有效提高了市域生态结构的完整性。研究结果可以为市域尺度生物多样性保护规划提供思路和方法。  相似文献   

12.
Natural forces and anthropogenic activities greatly alter land cover,deteriorate or alleviate forest frag-mentation and affect biodiversity.Thus land cover and forest fragmentation dynamics have become a focus of concern for natural resource management agencies and biodiversity con-servation communities.However,there are few land cover datasets and forest fragmentation information available for the Dhorpatan Hunting Reserve (DHR) of Nepal to develop targeted biodiversity conservation plans.In this study,these gaps were filled by characterizing land cover and forest frag-mentation trends in the DHR.Using five Landsat images between 1993 and 2018,a support vector machine algorithm was applied to classify six land cover classes:forest,grass-lands,barren lands,agricultural and built-up areas,water bodies,and snow and glaciers.Subsequently,two landscape process models and four landscape metrics were used to depict the forest fragmentation situations.Results showed that forest cover increased from 39.4％ in 1993 to 39.8％ in 2018.Conversely,grasslands decreased from 38.2％ in 1993 to 36.9％ in 2018.The forest shrinkage was responsible for forest loss during the period,suggesting that the loss of for-est cover reduced the connectivity between forest and non-forested areas.Expansion was the dominant component of the forest restoration process,implying that it avoided the occurrence of isolated forests.The maximum value of edge density and perimeter area fractal dimension metrics and the minimum value of aggregation index were observed in 2011,revealing that forests in this year were most fragmented.These specific observations from the current analysis can help local authorities and local communities,who are highly dependent on forest resources,to better develop local forest management and biodiversity conservation plans.  相似文献   

13.
Live fences may act as tools for biodiversity conservation by providing habitat for native species and increasing connectivity in the landscape. We studied the influence of live fence characteristics on species richness and fence use by birds by examining both local and landscape factors. We studied three types of live fences: planted fences of a native tree, planted fences of an exotic, and spontaneous. They were either connected to forest fragments or isolated, and were all within a pasture matrix. Spontaneous and planted live fences maintain a diverse plant (77 shrub and tree species) and bird communities (98 species). Fence types strongly differed in vegetation composition and structure. We found that by analyzing each fence characteristic independently, there was no difference in bird richness or abundance. However, there was a significant correlation when plant richness, structure, and connectivity were analyzed together. This could be the result of some variables counterbalancing each other. Birds used fences for a variety of purposes including foraging, breeding, and moving across the landscape. Native birds and plants used live fences as habitat and refuge in a landscape where large forest tracts have been lost for decades. Live fences in conjunction with small forest fragments maintain a diverse array of plant and birds species that are a subsample of the species originally found in the landscape before extensive deforestation. We recommend the establishment of live fences, allowing growth of spontaneous understory.  相似文献   

14.
Forest fragmentation has led to a decline in the population of many forest specialists, especially those with limited dispersal abilities. However, some of these species also occur in fragmented forests, and their response to fragmentation is crucial to understand the impact of this process in maintaining forest biodiversity. The objective of this study was to investigate the effects of habitat quality, quantity and configuration on the occurrence of Hazel Grouse as the model species. Studies were performed in the Carpathian Foothills (900?km2, 15?% forested). Between 2000 and 2010, Hazel Grouse were detected in 25 out of 53 forest patches with high repeatability over time. Among the indices of habitat quality, the most important factors were the presence of bilberries, clearings and pioneer trees. Greater number and length of valleys also had a positive effect on the occurrence of grouse. All habitat quantity and landscape configuration variables influenced the presence of grouse positively (related to forest connectivity) or negatively (related to forest isolation). Among the explanatory variables considered, habitat quantity and landscape variables were much more important in explaining the occurrence of Hazel Grouse than variables related to habitat quality. The study shows that habitat acreage and its connectivity are crucial for the conservation and management of Hazel Grouse populations in fragmented landscapes, and therefore, it is necessary to sustain wooded corridors between larger forest patches.  相似文献   

15.
Characterization of the suitability or potentiality of a territory for forest tree species is an important source of information for forest planning and managing. In this study, we compared a relatively simple methodology to generate potential habitat distribution areas that has been traditionally used in Spain (the potential index model) with a statistical modelling approach (generalized linear model). We modelled the potential distribution of mountain pine (Pinus uncinata) in the Iberian peninsula as a working example. The potential index model generated a map of habitat suitability according to the values of an index of potentiality, whose distribution has usually divided into four categories based on quartiles (from optimum to low suitability). Considering all values of the index of potentiality as presences of mountain pine resulted in a low to moderate degree of agreement between the potential index model and the generalized linear model according to the kappa coefficient. Using the cut-off value of the index of potentiality that maximized the degree of agreement between both modelling approaches resulted in a substantial similarity between the maps of the predicted distribution of mountain pine. This cut-off value did lie in the upper-third quartile of the potential index distribution (high suitability category), and roughly coincided with the upper 30th percentile. The use of statistical techniques, which have proved to be powerful and versatile for species distribution modelling, is recommended. However, the potential index model, together with the adjustments proposed here, could be a reasonably simple methodology to predict the potential distribution of forest tree species that forest managers should take into account when evaluating forestation and afforestation projects.  相似文献   

16.
练丽 《广东园林》2007,29(5):15-19
森林公园是指具有一定规模和质量的森林风景资源和环境条件,可以开展森林旅游,并按法定程序申报批准的森林地域。增城市南樵山森林公园规划,通过规划理念的创新探索、森林风景资源的调查与评价,提出森林公园的总体布局及游憩项目策划,阐述了如何在保护的前提下开展森林生态旅游。  相似文献   

17.
In an earlier study (Franc et al., 2007), local species richness of saproxylic oak beetles (including red-listed beetles) in forests was predicted mainly by the landscape (area of woodland key habitat within 1 km of plots). Such results are important for conservation work, but need to be backed up well, for reliable advice. We tested a two-stage method that improved our earlier models and our advice for conservation planning. We studied temperate mixed forest, rich in oaks Quercus robur/Quercus petraea, in a large landscape in Sweden. Franc et al. (2007) analysed 21 forests. Here we selected the significant explanatory variables (predictors) and other biologically relevant predictors, used the earlier 21 forests and sampled 11 new forests such that we expanded the range on the axes of the predictors. We collected in total 320 species of saproxylic oak beetles (23,137 individuals) of which 65 and 38 were red-listed (IUCN criteria, Swedish list 2000 and 2005, respectively). We partly confirmed our original results, but the results also changed in important ways: local species richness is now predicted by a combination of local, landscape and regional factors. Moreover, a local variable (dead wood) was the main predictor of saproxylic oak beetles (all species included), while for red-listed saproxylic oak beetles the landscape (woodland key habitat within 1 km of plots) was the main predictor, of local species richness. Thus, species richness of red-listed saproxylic oak beetles seems to depend mainly on landscapes factors, while total species richness of saproxylic oak beetles seems to depend more on local stand factors. We conclude that a two-stage research design can be useful in landscape and conservation studies, especially for species-rich taxa that require large samples per site.  相似文献   

18.
Stream–riparian areas represent a nexus of biodiversity, with disproportionate numbers of species tied to and interacting within this key habitat. New research in Pacific Northwest headwater forests, especially the characterization of microclimates and amphibian distributions, is expanding our perspective of riparian zones, and suggests the need for alternative designs to manage stream–riparian zones and their adjacent uplands. High biodiversity in riparian areas can be attributed to cool moist conditions, high productivity and complex habitat. All 47 northwestern amphibian species have stream–riparian associations, with a third being obligate forms to general stream–riparian areas, and a quarter with life histories reliant on headwater landscapes in particular. Recent recognition that stream-breeding amphibians can disperse hundreds of meters into uplands implies that connectivity among neighboring drainages may be important to their population structures and dynamics. Microclimate studies substantiate a “stream effect” of cool moist conditions permeating upslope into warmer, drier forests. We review forest management approaches relative to headwater riparian areas in the U.S. Pacific Northwest, and we propose scenarios designed to retain all habitats used by amphibians with complex life histories. These include a mix of riparian and upslope management approaches to address the breeding, foraging, overwintering, and dispersal functions of these animals. We speculate that the stream microclimate effect can partly counterbalance edge effects imposed by upslope forest disturbances, hence appropriately sized and managed riparian buffers can protect suitable microclimates at streams and within riparian forests. We propose one approach that focuses habitat conservation in headwater areas – where present management allows extensive logging – on sensitive target species, such as tailed frogs and torrent salamanders that often occur patchily. Assuming both high patchiness and some concordance among the distribution of sensitive species, protecting areas with higher abundances of these animals could justify less protection of currently unoccupied or low-density habitats, where more intensive forest management for timber production could occur. Also, we outline an approach that protects juxtaposed headwater patches, retaining connectivity among sub-drainages using a 6th-field watershed spatial scale for assuring well-distributed protected areas across forested landscapes. However, research is needed to test this approach and to determine whether it is sufficient to buffer downstream water quality and habitat from impacts of headwater management. Offering too-sparse protection everywhere is likely insufficient to conserve headwater habitats and biodiversity, while our alternative targeted protection of selected headwaters does not bind the entire forest landscape into a biodiversity reserve.  相似文献   

19.
Changes in historical forest composition and structure may have cascading effects throughout the forest community. Perhaps nowhere is there a better example of current forests that carry a legacy from their past than in eastern North America. The Cerulean Warbler (Dendroica cerulea), a declining Neotropical migratory bird of high conservation concern, is one excellent example of a species that seems to be sensitive to both landscape configuration and subtle features of eastern forests of North America. We used the Cerulean Warbler as a model species to demonstrate how an appreciation of fine-scale structural attributes of forests may improve our ability to conserve late-successional forest species. To do this we evaluated the extent to which multiscale habitat features were associated with density, spatial distribution, and nesting success of Cerulean Warblers in 12 mature forest sites in southeast Ohio, 2004–2006. Results suggest that adjacency of regenerating clear-cuts did not influence density or nesting success of Cerulean Warblers in adjacent mature forest. Instead, variation in demographic parameters was best explained by local habitat features. Density and nesting success were positively associated with canopy openness, numbers of large-diameter trees, and number of grapevines—all of which are typical of heterogeneous steady-state phase forests. Thus, improved management for Cerulean Warblers may require creating features (e.g., large canopy gaps) that mimic old-growth forests. Although fragmentation and habitat loss remain important contributors to population declines of many mature forest species, our work provides evidence that subtle changes in forest structure, particularly to features associated with old forests, warrant additional attention from the conservation community.  相似文献   

20.
Forestry has transformed the tree species composition and structure of Swedish forests. The fragmented ownership pattern in areas with non-industrial private forest ownership (NIPF), in combination with these forestry practices, have created fragmented forests with relatively low proportions of habitat types important to many species. Ecological landscape planning has been suggested and tested as a mean for integrating nature conservation and timber production in Sweden. However, ecological landscape planning concepts have been developed for areas with homogenous ownership patterns and not for areas with fragmented ownership. In this study, stands that are voluntarily set aside by individual forest owners were examined in terms of nature conservation value, and compared to randomly selected stands obtained by Monte Carlo simulation. In order to obtain rather detailed data about the set-aside stands, semi-standardized interviews were carried out directly with forest owners in three landscape areas dominated by NIPF. The interviews showed that 26 out of 29 forest owners could locate some stands where they did not have high requirements for timber yield. These stands had higher than average local and spatial nature conservation value as a result of stand structure, composition and location in the landscape. The stands did not have a random location or size, being found closer to key habitats as well as forming equally large or larger patches than other stands. These stands are suggested to form a basis for ecological landscape planning as forest owners seem to have some kind of ‘common view’ of which stands to set aside. This common view could be used to coordinate the contribution made by individual forest owners to nature conservation in areas with fragmented ownership patterns.  相似文献   

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