Post-fire habitat restoration of sables during winter season in northern slope of the Great Xing＇an Mountains

Habitat loss and fragmentation have been associated with the decline of endangered species. In 1987, a catastrophic fire in the northern Great Hing＇an Mountains of China, where the main habitat of sables （Martes zibellina） is located, aggravated the loss and fragmentation of the forest landscape. Due to restricted distribution and low population density, sables were listed in the national first-grade protected species in China. The objective of this paper was to identify to what extent the habitat of sables had been restored 13 years after the fire. Based on the behavioral data, which came from field survey information by radio-tracking, GPS （Global Positioning System） and forest inventory data, suitability habitat maps were derived using the Ecological Niche Suitability Model （ENSM）. In addition, the habitat structure was analyzed with selected landscape indices. Although forest cover mostly had been restored by 2000, the results indicated that, compared to the pre-fire situation, the areas of suitable habitat had been reduced significantly, especially those of less suitable, marginally suitable and moderately suitable designation. Fragmentation was aggravated, and suitable patches were found to be further isolated with the exception of those in most suitable areas. The ratio of the patch perimeter to area in unsuitable, moderately suitable and suitable areas decreased, while the ratios within other suitability types increased. Moreover, the percentage of soft boundaries decreased slightly, which can influence the redistribution of sables. The results above indicated that the suitable habitat had deteriorated, and the restoration of the sables＇ habitat remained to be done.     

Historical fire and vegetation dynamics in dry forests of the interior Pacific Northwest,USA, and relationships to Northern Spotted Owl (Strix occidentalis caurina) habitat conservation

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.     

湖南黄桑国家级自然保护区植被景观格局探讨

①斑块特征指数分析表明:各景观类型的密度、分维数指数都较小,植被景观的深展指数都不高,扩散比较均匀,没有极端复杂的形状产生,植被景观在演替系列中还没有普遍达到演替的顶级,斑块之间自相似程度较高。②多样性指数分析表明:总体多样性程度高。景观多样性指数、优势度指数与均匀度指数的结果所包含的意义一致,这种一致性充分说明了各植被景观类型分布均匀,各景观类型地位相差较小。③空间构型指数分析表明:保护区的斑块密度为1.001,即1 km2上有1.001个斑块。这说明斑块数目较少。各景观类型分布也较均匀。保护区景观破碎度指数为0.007,这表明该区植被景观在研究期内所表现的生境破碎化程度是很低的。每一植被景观类型破碎度指数最高的是灌丛和灌草丛景观,其次为栲林景观,其余的破碎度都处于较低的水平。内部生境破碎化指数以灌丛和灌草丛景观、栲林景观为最低,它们的单独斑块面积较大,故破碎化指数较低。其它景观类型的破碎化指数相差不大,这与植被顺向演替是相关的。景观分离度指数的排序结果与斑块密度的排序基本一致。     

Effects of multiple factors on plant diversity of forest fragments in intensive farmland of Northern Portugal

The joint and independent effects of dominant tree species, forest patch spatial attributes, and forest structure and management as drivers of plant species richness and composition in small forest patches scattered within an intensive agricultural landscape were addressed.In a landscape with scattered urban and intensive dairy agricultural areas in north-west Portugal, within which small forest patches (dominated by pines, eucalypts, or both) represent semi-natural habitat islands, 50 small forest patches, with areas ranging between 0.3 and 3 ha, were selected and surveyed for vascular plant diversity, within dairy farming landscape mosaics dominated by annual forage crops. Explanatory variables were composed of three datasets derived either from GIS mapping or field observations: forest type (dominant tree species), forest patch spatial attributes (patch area and shape index), and measures of forest management and structure (diameter at breast height, tree density per hectare, and percentage cover of vegetation strata). Variations in these forest patch attributes were assessed across forest types, and related to measures of plant diversity (total, native, alien, woody, and herbaceous species richness). Redundancy analysis with variance partitioning was applied to evaluate the joint and independent effects of the three sets of variables on species assemblages. The recent shift in canopy dominance from pine to eucalypt observed in the region appears to be related to a (nonsignificant) tendency for the increase of patch area and to the decrease of patch complexity, as well as several changes in forest structure and management, expressed as a trend to denser tree canopies and lower cover of understory plants. Dominant tree species and attributes related to forest structure and management were the most important factors determining plant diversity. The joint effect of the dominant tree species and forest structure and management resulted in lower levels of plant species richness in eucalypt plantations. These were also more prone to invasion by alien species, probably due to decreased biotic resistance from unsaturated native plant assemblages. Our results draw attention to the importance of dominant tree species and management practices for the maintenance of plant diversity levels (species richness and composition) in dairy landscape mosaics, highlighting the importance of the remnants of semi-natural forests as refuges for plant diversity in the landscape context. Nonetheless, forest plant diversity could further be fostered by promoting naturalness of pine stands and the regeneration of native oak woodlands in some forest areas. This would also diversify the range of ecosystem services that could be provided by forest areas in these peri-urban farmlands.     

Ruffed grouse-habitat preference in the central and southern Appalachians

Ruffed grouse (Bonasa umbellus; hereafter grouse) populations in the central and southern Appalachians (CSA) are declining due to widespread maturation of forest cover. Effective management of this species requires a sex- and age-specific understanding of habitat preferences at multiple temporal and spatial scales. We used multivariate logistic regression models to compare habitat within 1440 grouse home ranges and 1400 equally sized buffered random points across 7 CSA study areas. On most sites, grouse home ranges were positively associated with roads and young forest (<20 years old). Sex and age status affected habitat preference. In general, males used younger forest than females, likely because of differences in habitat use during reproductive periods. Juveniles had fewer vegetation types preferred by adult grouse and more of the avoided vegetation types within their home ranges, indicative of competitive exclusion. Adult females had the greatest specificity and selectivity of habitat conditions within their home ranges. Habitat selection varied among seasons and years on most sites. Winter habitat use reflected behavior that maximized energy conservation, with open vegetation types avoided in the winter on the northernmost study areas, and topography important on all areas. Summer habitat selection reflected vegetation types associated with reproductive activities. Scale influenced habitat preference as well. Although roads and forest age predominantly influenced grouse home range location within the landscape, mesic forest types were most important in determining core area use within the home range. This was likely a result of increased food availability and favorable microclimate. Habitat management efforts should attempt to maintain ∼3–4% of the landscape in young forest cover (<20 years old), evenly distributed across management areas. Roads into these areas should be seeded as appropriate to enhance brood habitat and provide travel corridors connecting suitable forest stands.     

Effects of forest structure and microhabitat on the distribution and flowering of a rare understory plant, Actaea elata

Knowing which environmental characteristics constrain forest understory species’ distribution and reproduction can inform conservation decisions about habitat management and locations for reintroduction efforts. Differential plant performance is common in varying environmental conditions, such as levels of canopy closure. Actaea elata (tall bugbane) is a rare, perennial, forest understory herb found from Oregon to British Columbia. Populations throughout this species’ range commonly occur in managed forests. We assessed the importance of environmental variation on the distribution and flowering of A. elata at both microhabitat and site-level scales. At four sites encompassing a variety of forest types, we measured several biotic and abiotic variables at vegetative and reproductive plants, as well as at random points. We measured these same variables at three sites where A. elata has been extirpated. Within occupied sites, reproductive plants were more likely to be located in canopy gaps than were vegetative plants. Both vegetative and reproductive plants were more likely to be found in areas of high herb cover compared to random points. These results indicate that gaps in the canopy may be critical for this species’ ability to reproduce, but survival may be possible in a broader range of forest understory conditions (similar to other co-occurring herb species). Random points at extirpated and occupied sites both tended to be located in areas of lower canopy openness and moisture availability than points in occupied sites where A. elata was present. Extirpated sites were either densely forested or clearcut, while occupied sites contained stands of intermediate density. Circaea alpina, Geranium robertianum, and Lactuca muralis were indicator species for A. elata and normally indicate moist soils, with Circaea alpina being a strong indicator of the presence of flowering A. elata. Taken together, our results suggest that maintenance of canopy gaps is important to promote flowering, and understory species that indicate moist sites, particularly Circaea alpina, can be used as aids to locate new populations of A. elata.     

Short-term response of the herbaceous layer within leave patches after harvest

Leave patches, uncut areas in a harvested forest, may conserve herbaceous layer species that decline after forest clearcutting. They may also serve to maintain source populations for the recolonization of the harvest area. The main objective of this study is to characterize the short-term response of the herbaceous layer to clearcut harvesting disturbance within and adjacent to leave patches. Four experimental 1 ha patches and two uncut references were established. Within each patch or reference, belts of five 1 m² quadrats were placed at 50 m and 5 m outside the patch, at 0 m (edge), and at 25 m, 35 m, and 50 m (centre) inside. These belts of quadrats were replicated at all four aspects (North, South, East, and West). Ground vegetation was sampled yearly for 1 year before harvest and 3 years after harvest in the experimental patches and for 2 consecutive years in the references. Some common residual species declined significantly in the clearcuts, but remained stable inside the patches in the short term (3 years after harvest). Overall species composition changed little in the patch interior and edge after harvest. Colonizing species (those that appeared in quadrats after harvest) in the patch exterior were predominantly early-seral species, whereas colonizers in the patch interior tended to be shade-tolerant forest species. Species were grouped a priori based on two habitat preferences (amounts of canopy cover and disturbed substrate). Species characteristic of a habitat with closed canopy and undisturbed substrates that decreased significantly over time in the patch exterior were negatively correlated with the amount of exposed mineral soil and open canopy. Species characteristic of a habitat with open canopy and disturbed substrates that increased significantly at the patch exterior showed a positive correlation with the amount of exposed mineral soil and open canopy. No species’ habitat preference groups declined significantly in the patch interior or edge over time. Based on species’ responses to forest operations, it appears that at least the common forest species are maintained in the short term within leave patches.     

一个世纪来黑龙江省森林景观动态研究

With the help of GIS tool of ARC/INFO,ARCVIEW and FRAGSTATS,the map of forest resource distribution of Heilongjiang Province was analyzed in 1896,1949 and 1981.Using total area,mean patch size,patch density,coefficient of patch size variation,mean patch fractal dimension and mean shape index,we studied the change of forest landscape pattem and the change of each patch types in this region.As a result,the total area of forest landscape and mean patch size decreased sharply,the quantity and density of patches increased,the juxtaposition of patches weakened,the shape of patch tended to become regular,and the border of patch simplified.All these showed that the forest landscape of this area tended to fragment gradually,and the fragment of Korean pine forest is the severest.the diversity of whole forest landscape and the eveness of landscape types distribution reduced gradually.Human impact,instead of climate change and forest community succession,is the most important reason for such dramatic chages.     

Modelling jay (Garrulus glandarius) abundance and distribution for oak regeneration assessment in Mediterranean landscapes

Because natural regeneration of oak is strongly dependent on jay abundance and distribution, we need to understand the determinants of jay abundance and occurrence as a first step to assess oak regeneration. In this paper we modelled the jay population distribution and abundance in a Mediterranean landscape mosaic of the eastern Iberian Peninsula (Valencia, east Spain). The methodology was based on assessing landscape attributes (habitat composition and configuration variables) on seven 9-km² sites and registering jay fledgling locations. Using a stepwise regression model we determined the variables that best explained the jay density. The probability of occurrence of jay nests within each site was assessed by comparing the landscape attributes of jay and non-jay areas within each site. Results were validated by predicting each site on the basis of data from the remaining six sites and then calculating the deviation between the predicted and the observed values in the field. The results suggest that jay density correlates positively with forest cover and landscape heterogeneity variables, and negatively with shrubland cover. Validation of the results showed that the model is reasonably effective in predicting both jay abundance and distribution at the extent and resolution used.     

How well does Kirtland's warbler management emulate the effects of natural disturbance on stand structure in Michigan jack pine forests?

Jack pine (Pinus banksiana) forests in parts of northern Lower Michigan have been managed with 30 years of extensive clearcut harvesting followed by planted stand establishment in order to maintain habitat for the endangered Kirtland's warbler (Dendroica kirtlandii). We used two, parallel chronosequences to study how this management has affected the structural development of jack pine stands relative to the historically dominant disturbance regime of stand-replacing wildfire. Each chronosequence consisted of three young stands (age range 3–6 years), three intermediate-aged stands (age range of 12–17 years) and three mature stands (age range of 39–69 years). Average stem density in young plantations (2300 stems/ha) was lower than the average for young, fire-origin stands (11,000) and varied over a much narrower range among stands (1403–2667 for plantations and 1552–24,192 in fire stands). In addition, within-stand patchiness of stem density was also much higher in the wildfire sites for young and intermediate ages. Plantation sites possessed very little dead wood at young ages (averaging 3 snags/ha and 12 m³/ha CWD) compared to young fire-origin stands (averaging 252 snags/ha and 49 m³/ha CWD). In contrast, mature plantations had similar levels of dead wood (averaging 269 snags/ha and 22 m³/ha CWD) as mature fire-origin stands (averaging 557 snags/ha and 12 m³/ha CWD). Differences between the plantation and fire-origin chronosequences were driven mainly by young- and intermediate-aged stands, whereas mature stands were typically quite similar in all structural features. Our results show clearly that forest management aimed at preserving and enhancing the population of a single endangered species results in greatly simplified habitat structure at the stand level, and suggest that this simplification is perpetuated across the landscape as well. Of particular concern are the effects of extensive harvesting and planting on the availability of snags and CWD.     

Avian population and community processes in forest ecosystems: Long-term research in the Hubbard Brook Experimental Forest

Long-term studies in relatively undisturbed forest ecosystems, such as occur in many of the USFS’ Experimental Forests, provide valuable insight into bird population and community processes, information pertinent to forest management and bird conservation. Major findings from 40 years of research in the Hubbard Brook Experimental Forest in north-central New Hampshire reviewed here show that the distributions and abundances of bird species are dynamic, even within well-developed and mature forests, and that species respond differently to habitat (vegetation) structure, food availability, and other features of the forest environment. At the local scale, bird population demography is most affected by factors that influence fecundity and recruitment, mainly food availability, weather, nest predators, and density dependent processes. Fecundity is strongly correlated with subsequent recruitment and is critical for maintaining breeding population size. Events in the non-breeding season, however, also influence the abundance and demography of breeding populations, indicating the need to assess factors operating throughout the species’ annual cycle. At the landscape scale, populations in temperate forests are spatially structured by each species’ response to habitat and environmental patterns, but also by social interactions such as competition and conspecific attraction. Settlement patterns and ultimately reproductive performance depend on habitat quality, based on vegetation structure, food availability and nest predator effects that vary across the landscape. Results from these long-term studies centered at Hubbard Brook provide a mechanistic understanding of avian population dynamics and community responses. The results provide a framework for predicting how future changes in habitat quality, climate, and other environmental threats may influence bird populations and communities in north-temperate forests.     

Variation in moth occurrence and implications for foraging habitat of Ozark big-eared bats

We investigated patterns of moth occurrence among habitats in two different landscapes surrounding roosts of the endangered Ozark big-eared bat (Corynorhinus townsendii ingens) from May to August 2005, and compared these data with published results on the diet of this subspecies. Landscapes were situated in the Ozark Mountains, USA, and consisted of a fragmented, agricultural landscape and a contiguous national forest. We captured 8720 moths constituting ≥314 species and 22 families. Pastures demonstrated a lower abundance and richness of moths than other habitats in the fragmented landscape (p < 0.05). Neither abundance nor richness of moths varied by habitat in the forested landscape, but we did observe variation among roost locations (p < 0.05). Abundant families of moths (n ≥ 100 specimens captured) did vary in abundance among habitats in both landscapes (p < 0.05), with poletimber stands, riparian forest and upland forest selected, and pasture, forest edge, sawtimber and sapling stands avoided by at least one family of moths. Density and richness of woody plant species were correlated with the occurrence of moths at sampling sites. We recommend maintaining habitat heterogeneity around roosts of the Ozark big-eared bat to encourage an abundance and richness of moth prey, and suggest that forested riparian corridors are important habitat elements for Ozark big-eared bats foraging in fragmented landscapes.     

Integrating landscape connectivity in broad-scale forest planning through a new graph-based habitat availability methodology: application to capercaillie (Tetrao urogallus) in Catalonia (NE Spain)

The loss of connectivity of forest landscapes is seriously hindering dispersal of many forest-dwelling species, which may be critical for their viability and conservation. In this context, explicitly incorporating connectivity considerations is an important challenge in current forest planning and management, but as yet there is a lack of operative methods for appropriate decision making in this respect. We describe a new methodology based on graph structures and a habitat availability index (integral index of connectivity) that integrates forest attributes (like habitat quality) and network connectivity in a single measure. We apply this methodology to examine the connectivity of the highly fragmented habitat of capercaillie (Tetrao urogallus) in Catalonia (NE Spain), where the threatened status of this forest bird species calls for landscape-level forest planning solutions. We analyse data on the distribution of capercaillie forest habitat at 1 km spatial resolution obtained from the recent Catalan Breeding Bird Atlas. We determine the functionally connected regions existing within its habitat distribution and identify the forest habitat areas that are more important for the maintenance of overall landscape connectivity for this species. Based on these results, we provide recommendations on certain critical public forests where management oriented to the conservation of capercaillie habitat is more necessary. These results highlight the potential and practical interest of the proposed methodology for successfully integrating landscape connectivity in broad scale forest planning.     

Measuring ecologically important quantities at relevant operational scales: An example using the dusky flycatcher in selectively logged forests in Idaho

Effective management of forest wildlife requires information about habitat features that can be altered by operations, if those habitat features promote reproductive success and survival, and if changes in organism density influence reproductive success and survival. Habitat selection studies often provide the first type of information, although relatively few studies examine how different selection decisions or densities of organisms influence fitness measures or measure habitat features at relevant operational scales. We examined patterns of habitat selection and estimated how habitat use, territory size, and conspecific density were associated with territory success (probability of a territory producing one or more fledglings) for the dusky flycatcher in 2002–2003 on eight study plots in managed grand fir (Abies concolor) forests in Idaho, USA. Flycatchers selected territories with greater cover of deciduous vegetation in two different height strata (1–2 and 3–4 m) and reduced cover of conifers less than 4 cm dbh compared to what was available. While flycatchers selected habitat characteristics at the territory scale, model selection results did not support any associations between vegetation features and territory success. Territory success had weak positive associations, for a given territory size, with conspecific density, although the relationship was highly variable. An interaction between territory size and density was not supported. These results are consistent with the view that avian breeding habitat selection occurs at multiple scales, and that the nest site scale may explain more of the variance in reproductive success than larger scales. Our results suggest that operational management of vegetation features, which often occurs at the stand scale, may not influence variation in critical demographic metrics. Increasing total shrub cover of commonly used plant species should benefit the dusky flycatcher, as well as other shrub-nesting forest birds, but stand-level habitat alterations alone cannot be relied upon to increase reproductive success, an important component of population change.     

The confluence of landscape context and site-level management in determining Midwestern savanna and woodland breeding bird communities

Species distributions are determined by complex interplays between multi-scale factors. Conservation management, however, often occurs at a single scale of the site level. This is true for bird communities of restored savannas and mixed woodlands in the central U.S. In this region, many historic open-canopy oak savanna habitats have become closed canopy mixed woodlands due to loss of landscape-scale disturbance from fire and grazing. Site-level management efforts return some mixed woodland habitats back to savanna through fire and mechanical thinning. Savanna and woodland historically formed complex mosaic landscapes at the ecotone between prairies and Eastern deciduous forests and now exist within landscapes that vary in amount of open (e.g., perennial grassland and row crop agriculture) and woodland habitat. To understand the interplay between site and landscape level factors in savanna restoration, we sampled the breeding bird community in four combinations of site and landscape: restored savanna in open landscapes, restored savanna in woodland landscapes, and closed canopy woodland in both landscapes. We found that the outcome of site-level savanna restoration depended on the surrounding landscape. Compared to other treatment types, restored savannas in open landscapes supported a distinctive bird community characterized by high species richness, bird abundance, and percent of ground feeders, shrub nesters, and edge species. Both savanna and woodland sites in the open landscape had a higher percent of species of conservation concern, while at both site and landscape levels, woodland was associated with a higher percent of area sensitive species and habitat specialists. Our results suggest savanna restoration efforts should focus on sites that exist either in open country or on edges where closed canopy forest meets open country. This strategy would combine site and landscape level benefits of savanna restoration for avian diversity, while also preserving the conservation benefits of large tracts of intact forest.     

Relationship between landscape structure and burn severity at the landscape and class levels in Samchuck, South Korea

Fuel treatments for reducing fire risk are necessarily tied to the landscape structure including forest composition and configuration. Thus understanding the relationships between landscape structure and burn severity is important for developing guidelines and management strategies for fire-resilient forests. The goal of this study was to investigate the relationship between landscape structure as described by spatial pattern metrics and burn severity at the landscape and class levels. In 2000, a mostly severe fire burned 16,210 ha of dense forest located in Samchuck on the east coast of the Korean peninsula. Spatial pattern metrics including patch density, largest patch index, mean shape index, area-weighted mean shape index, Euclidean nearest neighborhood distance, and Shannon's diversity index, as well as topographic characteristics of slope and elevation, were correlated with burn severity based on delta Normalized Burn Ratio (dNBR) assessments. Regression tree analysis was also carried out with the same variables to avoid spatial autocorrelation and to reveal the relative importance of variables to burn severity. The results of this study strongly suggest that both composition and configuration of the forest cover patches are closely tied to burn severity. In particular, both the correlation analysis and regression tree analysis indicated that the area of red pine tree forest cover was the most significant factor in explaining the variance of burn severity. Topography and spatial configuration of forest cover patches were also significantly related to burn severity. The heterogeneity of forests also had a significant influence on burn severity. To reduce fire risk and increase the fire resilience of forests, forest managers and agencies need to consider enhancing the heterogeneity of forests when implementing fuel treatment schemes. However, such fuel treatments for landscape structure may only be effective under moderate weather conditions.     

Mammals of Cabo Blanco: History,diversity, and conservation after 45 years of regrowth of a Costa Rican dry forest

Reserva Natural Absoluta Cabo Blanco, a strongly seasonal deciduous forest located at the southernmost tip of northwestern Costa Rica's Nicoya Peninsula, was established in 1963 and is the country's oldest nationally protected reserve. The peninsula has been occupied for millennia and is a heavily impacted landscape, and, unfortunately, its biotic diversity is among the most poorly studied in Central America. As part of multiyear studies of the flora and fauna of the region, we assess the changes in vegetation and the terrestrial mammal community from earlier times to the present day. Through historical records, interviews with long-term residents of the area, and our studies over the past decade, we document changes in forest cover, settlement, and land use, and assess the changes in species diversity and in mammal species’ abundance. We then discuss the ecology of the mammal species on the peninsula, emphasizing the role that humans have played in influencing population levels.     

Do the size and landscape context of forest openings influence the abundance and breeding success of shrubland songbirds in southern New England?

Early successional birds have declined in the northeastern United States due to the regeneration of forest on abandoned farm fields and the suppression of natural disturbances that once provided appropriate habitat. These species have become increasingly dependent on early successional habitats generated by such activities as timber harvesting. Recent approaches of timber harvesting, which range from single-tree harvesting to clearcutting, create forest openings of different sizes and configurations embedded in landscapes with different land use patterns. To assess the importance of forest openings created by timber harvesting for shrubland birds, we surveyed birds on 50 m radius plots in 34 harvest sites (0.5–21 ha). We collected data on multi-scaled habitat variables ranging from plot-level vegetation characteristics to land use patterns within 1 km of each study site. We also monitored mating and nesting success of Blue-winged Warblers (Vermivora pinus) in 10 forest openings.

The abundance of most shrubland species was influenced by plot-level habitat variables, such as tree density and vegetation height, rather than shrubland area or the composition of land uses in the surrounding landscape. Only Eastern Towhees (Pipilo erythrophthalmus) were more frequent in survey plots in larger forest openings. In contrast, neither abundance nor reproductive activity of Blue-winged Warblers was correlated with the size of the forest opening. Their abundance was negatively related to vegetation height, however. Only 54% of the territorial male Blue-winged Warblers in forest openings were mated. We documented relatively low nest success rates of 21.1% during the egg laying and incubation nest stages, but increased success rates during the later stages of nesting.

Our results indicate that even small forest openings with low vegetation provide habitat for Blue-winged Warblers and other shrubland birds. The overall reproductive rate of territorial male Blue-winged Warblers in forests openings was low during the 2 years of the study, however. Further studies are needed to assess the long-term value of this type of habitat for sustaining shrubland bird populations.     

Differential effects of vegetation restoration in Mediterranean abandoned cropland by secondary succession and pine plantations on bird assemblages

Two contrasting trajectories for vegetation restoration in agricultural landscapes are secondary succession following cropland abandonment that can regenerate woodlands (passive restoration) and conversion of cropland to tree plantations (active restoration), which have mostly focused on pine species in the Mediterranean Basin. We compared the effects of these two contrasting trajectories of vegetation restoration on bird assemblages in central Spain. Vegetation structure differed in the two restoration trajectories, pine plantations attaining higher tree cover and height (31% and 4.1 m, respectively) but lower strata complexity than secondary shrubland and holm oak woodland (which attained 10% and 1.4 m of tree cover and height, respectively). Bird species richness differed in stands under active or passive restoration trajectories, the former collecting a higher total number of species (4.2 species per 0.78 ha plot) than the latter (3.5 species per plot). The number of forest species increased with vegetation maturity in both restoration trajectories, but especially in stands under active restoration. The occurrence of woodland generalist species increased and of species inhabiting open habitats decreased in actively restored stands, being some of these latter species of high conservation priority in the European context but relatively common at the regional level. Bird species inhabiting pine plantations had broader habitat breadth at the regional level than those inhabiting secondary shrublands and woodlands. Maximum regional density did not differ between both restoration trajectories, but it increased with development of the herbaceous layer only at the secondary succession trajectory. The relative importance of species of European biogeographic origin was higher in mature pine plantations (58.9% of total bird abundance) than in mature holm oak woodlands (34.4%), whereas that of Mediterranean species was considerably higher in the latter (40.1%) than in the former (20%). Bird assemblages of relatively small patches of pine plantations are unable to reflect the regional avifauna, in contrast with the relationships between local and regional assemblage characteristics that can be found in isolated natural forests. We conclude that programs of vegetation restoration should base upon a range of approaches that include passive restoration, active restoration with a variety of tree and shrub species, and mixed models to conciliate agricultural production, vegetation restoration and conservation of target species.     

岷山山系土地岭大熊猫栖息地廊道特征及影响因素分析

本文采用景观生态学的斑块理论,根据土地岭区域前后两期森林分布信息和大量的野生动植物以及社会经济信息,详细分析了土地岭区域建立大熊猫栖息地走廊带的植被分布格局、斑块结构、廊道特征及主要影响因素,研究结果显示土地岭区域植被符合大熊猫栖息地建设条件。残余班块分布连续,占据区域森林植被的主体,有利于廊道栖息地恢复。引进斑块面积大,质量差,是廊道栖息地建设的主要改造类型。在众多的社区活动影响中,采笋的负面影响最大,最值得重点关注。基于一些主要因素的分析,作者提出了在土地岭建立大熊猫栖息地走廊带的关键措施。