首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
There is a growing realisation world over that the introduction of modern agriculture has to be supplemented with measures to conserve biodiversity in situ if yield gains are to be stabilized. Hence, there is a growing interest from agricultural development specialists and conservation biologists for understanding the socioeconomic factors determining the conservation of biodiversity in situ. The present study was conducted with the objective of understanding the in situ (on-farm) conservation of agrobiodiversity in traditional agroecosystems taking the Urgam valley in north-western Himalaya of India, as a case study. An inventory was made of traditional crops and wild economic species for subsistence, and the structure of forest resource base, traditional knowledge related to resource management and use. Institutional and scientific challenges for in situ (on-farm) management of crop diversity were studied and are discussed in this paper. Complementarity of in situ (on-farm) conservation with ex situ conservation together with crop improvement in such marginal areas are suggested.  相似文献   

2.
Significant biodiversity loss is characteristic of agricultural landscapes worldwide. Biodiversity recovery efforts in such landscapes can be hamstrung by a paucity of information on factors affecting species’ distributions, particularly for threatened and/or declining species. The temperate woodlands of south-eastern Australia have been extensively modified for agriculture and numerous bird taxa are declining. We have explicitly identified habitat and landscape attributes of woodland remnants affecting site occupancy by 13 woodland bird species of conservation concern.Using case-control data and linear logistic regression, we found that site occupancy for each species was related to both habitat and landscape variables. Habitat variables of particular importance included those in the ground layer (an abundance of leaf litter, an intact surface crust of mosses and lichens and a scarcity of annual grasses) and overstorey (a scarcity of eucalypt dieback and an abundance of mistletoe). Landscape variables strongly affecting site occupancy included the number of paddock trees and the area of native grass within 500 m of a site. Many of our study species were found most often in regrowth remnants.Our findings indicate a gap between current conservation practices and the actual habitat requirements of woodland bird species of conservation concern. Successful management will require protection and/or rehabilitation of the ground layer and overstorey of woodland remnants and sympathetic management of the surrounding landscape. It also will require managers to go beyond current practices of conserving old growth remnants and establishing replantings to maintaining and creating stands of woodland regrowth.  相似文献   

3.
《Biological conservation》1986,37(2):135-156
The reptile communities on two islands off the north coast of Mauritius are described. One of these islands, Round Island, is the last refuge for four species: Phelsuma guentheri, Leiolopisma telfairii, Bolyeria multocarinata and Casarea dussumieri, which together with four more species form a relict herpetofauna of great scientific and conservation interest. The reptile fauna of the neighbouring island of Gunner's Quoin has been reduced to four species, probably because of habitat destruction and the effects of ship rats Rattus rattus. Round Island has also suffered habitat destruction through introduced mammals but because of its remoteness, rats are absent. Conservation of the Round Island ecosystem is discussed; removal of the remaining alien herbivores, the rabbit Oryctolagus cuniculus and conservation education about Round Island are the main recommendations.  相似文献   

4.
Despite its size and attractiveness, many Lucanus cervus sites remain undetected in NW Europe because of its short flight period and its nocturnal activity. Therefore, present-day designated conservation areas for L. cervus are probably insufficient for a sustainable conservation of the species. We applied eight species distribution modelling techniques (artificial neural networks, classification tree analysis, generalised additive models, generalised boosting models, generalised linear models, mixture discriminant analysis, multiple adaptive regression splines and random forests) to predict the distribution of L cervus in Belgium using 10 randomly generated calibration and evaluation sets. We used AUC, sensitivity (% correctly predicted presences in the evaluation set) and specificity (% correctly predicted absences in the evaluation set) and Kappa statistics to compare model performances. To avoid the incorporation of only marginally suitable woodland sites into the Natura 2000 network, we, conservatively, considered the species as being present only in grid cells where all 10 randomly generated model sets predicted the species as such. Model performance was, on average, good allowing to predict the potential distribution of L. cervus accurately. According to the predicted distribution using the more robust prevalence threshold, only 5731 ha (11% of the potentially suitable area) is protected under the Natura 2000 scheme in Belgium. Subsequently, we categorised the potentially suitable woodlands into three conservation priority categories based on their surface area and the already designated Natura 2000 area. Including the most suitable L. cervus woodlands previously not included in the Natura 2000 sites within such network would require protecting an area of 15,260 ha. Finally, we discuss the implications of using species distribution modelling for nature policy decisions in designating conservation networks.  相似文献   

5.
Small mammals, such as European rabbits (Oryctolagus cuniculus), plateau pikas (Ochotona curzoniae) and prairie dogs (Cynomys spp.), traditionally have been perceived as pests and targeted for control within their native ranges, where they perform essential ecosystem roles and are considered keystone species. These species can reach high densities, and have been subjected to eradication campaigns because of their putative negative impact on natural habitats and agriculture and their competition with livestock for forage. Eradication programmes have been a main factor causing sharp declines of these species in their natural ranges. Paradoxically, they are keystone species where they are abundant enough to be perceived as pests. The term “pest” is usually a social perception that is rarely supported by scientific data, whereas there is considerable scientific evidence of the key ecological roles played by these species. We call for the conservation of these species and present a conceptual model regarding the management of their populations. Where they occur at high numbers, and hence their effects on biodiversity are still of crucial importance, the persecution of these species should be avoided and their natural habitats preserved. In areas with high conservation value, but where these species occur at low densities, management efforts should aim to increase their density. In areas of high commercial value, managers ideally should consider changing prioritization of the area to high conservation value by purchasing the land or obtaining conservation easements. In situations with high commercial value and demonstrable low conservation concern, small mammals could be reduced humanely.  相似文献   

6.
This paper briefly reviews some of the problems of nature conservation in Sweden and the legislative and other measures which have been recently taken in this field. The organisation and responsibility of different conservation bodies are described. An intensive debate about activities such as localisation of industries inimical to the environment, modern forestry and off-road driving has resulted in new guidelines or legislative measures in recent years. Site protection by means of the Nature Conservancy Act is believed to be the most effective way of safeguarding areas valuable to scientific conservation and outdoor recreation. Some examples of fauna preservation and habitat management are mentioned.  相似文献   

7.
This study investigated associations between the relative abundance of the threatened ngwayir (western ringtail possum, Pseudocheirus occidentalis) and anthropogenic disturbances at local and landscape scales within the publicly-managed jarrah (Eucalyptus marginata) forests of south-western Australia. Logging, fire, fox (Vulpes vulpes) control and forest fragmentation were investigated in relation to the relative abundance of ngwayir at 90 sites within an area of 285,000 ha east of Manjimup; the location of the last remaining substantial population of ngwayir in jarrah forest. Overall, ngwayir abundance was greatest in areas with limited anthropogenic disturbance. At the local-scale, ngwayir abundance was negatively associated with greater fire intensity. At the landscape-scale, it was positively associated with fox control and negatively associated with forest fragmentation and distance from non-remnant vegetation (i.e., agriculture and tree plantations). Abundance was also greatest in predominantly unlogged landscapes and in forests that had been regrowing for an average of 40 years since the landscape was most recently logged, in other words, where logging was historically least intense. Interactions between fox control efforts and forest fragmentation were also important. This study emphasises the importance of conducting research at appropriate spatial scales and to account for the synergistic effects of the causes of decline. An adaptive management approach to the mitigation of the agents of decline is recommended.Indirect evidence indicates that high value habitat for ngwayir has in all likelihood been selectively cleared for agriculture, owing to its fertile and productive nature. Habitat loss is, therefore, also likely to be a major cause of the modern decline of the species. While many jarrah forest areas that support remaining high abundances of the ngwayir have been incorporated into reserves, conservation of ngwayir habitat and populations outside reserves also will be essential for the recovery and long-term viability of the species.  相似文献   

8.
Forest exploitation has destructed forest habitats in Fennoscandia during last centuries. Vital components of existing forest biodiversity have been identified as small (a few ha) woodland key habitats (WKHs). Many WKHs in boreal forest landscapes are assumed to represent remnant near-natural forests from before the phase of industrial forest exploitation. Thus, WKHs are supposed to (i) exhibit a low degree of exploitation, (ii) have old-growth characteristics and (iii) host Red-list species. Yet, WKHs’ history and biodiversity have not been systematically investigated. Thus, their conservation values remain unclear. This study investigates history and biodiversity of 15 WKHs in central Sweden with retrospective methods and field studies. We analyze (1) forest structure before, during and after the forest exploitation period, (2) existing biodiversity, i.e. species and structural elements, and (3) to what extent human activities (forestry) have influenced current biodiversity. Our results indicate that forest structure within the areas that currently are classified as WKHs has changed dramatically since the mid-19th century, when forests were unaffected by logging. The results suggest that fire-suppression during last century, gradually increased logging until mid-20th century and abandonment by modern forestry during the late 20th century, are main causes behind this transformation. Less than 10% of studied WKHs had biological features that resembled those of pristine boreal forests. Thus, most studied WKHs cannot be classified as near-natural or remnants of pristine forest. We suggest that the program for WKHs give more focus to pre-industrial forest structure, local historical aspects being seriously regarded and ecological restoration efforts being introduced.  相似文献   

9.
Between 1937 and 1983 a total of 391 400 ha of woodland, representing 51% of the 768 900 ha in the Zambia Copperbelt, had been deforested for industrial and household woodfuel. This has occurred in spite of a forest reservation programme that increased the area in forest reserves from 31 707 ha in 1942 to 252 715 ha in 1965. Between 1965 and 1980 the reserved forests were reduced to 246 930 ha and since then the area has remained static. The rapidly growing demand for charcoal by the increasing urban population, and the growing problem of acid dust and rain pollution from copper smelters, pose serious threats to forest conservation in this industrial region of Zambia. Current forest conservation is restricted to the establishment of exotic forest plantations and recently deforested areas are left to regenerate naturally.Forest destruction and conservation in the Copperbelt area were studied and the structure of old-growth and coppice woodland stands at 9 and 14 sites, respectively, investigated during 1982–1984. The Copperbelt vegetation is dominated by Brachystegia-Julbernardia woodland. Mean species diversity of 24·40·1 ha−1 in coppice stands was higher than that of 18·9 found in old-growth stands. Stem density in coppice was 3·3 times that observed in old-growth woodlands. The majority of species (over 50%) in both old-growth and coppice were represented by less than 11 stems per sampling plot. Mean basal area at breast height in coppice aged 19–23 years was 14·33 m2, which was 95% of the mean basal area of 15·15 m2 found in old-growth woodlands.  相似文献   

10.
Prioritization of conservation efforts for threatened and endangered species has tended to focus on factors measuring the risk of extirpation rather than the probability of success and cost. Approaches such as triage are advisable when three main conditions are present: insufficient capacity exists to adequately treat all patients, patients are in a critical state and cannot wait until additional capacity becomes available, and patients differ in their likely outcome and/or the amount of treatment they require. The objective of our study was to document the status of woodland caribou (Rangifer tarandus) herds in Alberta, Canada, with respect to these three conditions and to determine whether a triage approach might be warranted. To do this we modeled three types of recovery effort - protection, habitat restoration, and wolf control - and estimated the opportunity cost of recovery for each herd. We also assessed herds with respect to a suite of factors linked to long-term viability. We found that all but three herds will decline to critical levels (<10 animals) within approximately 30 years if current population trends continue. The opportunity cost of protecting all ranges by excluding new development, in terms of the net present value of petroleum and forestry resources, was estimated to be in excess of 100 billion dollars (assuming no substitution of activity outside of the ranges). A habitat restoration program applied to all ranges would cost several hundred million dollars, and a provincial-scale wolf control program would cost tens of millions of dollars. Recovery costs among herds varied by an order of magnitude. Herds also varied substantially in terms of their potential viability. These findings suggest that woodland caribou in Alberta meet the conditions whereby triage should be considered as an appropriate conservation strategy.  相似文献   

11.
Work in many parts of the world has discussed the decline of biodiversity in regions dominated by agriculture. We report the results of a major study documenting the longitudinal profiles of birds between 1998 and 2009 within 66 patches of temperate woodland in a heavily cleared and grazed agricultural region of south-eastern Australia. Many researchers have forecast the loss of bird biota from this region and others that also were formerly dominated by temperate woodland.We had sufficient high quality data to analyse the longitudinal profiles of reporting rates for 76 of the 116 individual bird species recorded in our 12-year study. Unexpectedly, only four of the 76 species analysed (5.6%) exhibited a significant negative linear decrease in reporting rate. More surprisingly, 32 (42.1%) exhibited a significant positive linear increase in reporting rate, including several taxa of conservation concern. These increases occurred despite a series of below-average rainfall years. Reporting rates were too low to formally model long-term trends in some other bird species widely considered to be of conservation concern such as the Diamond Firetail (Stagonopleura guttata) and Speckled Warbler (Chthonicola sagittata).Many authors have used functional (and other) groups to forecast bird species likely to be lost from Australia’s temperate woodlands. However, we found no clear links between life history attributes and long-term trend patterns of species.Our findings contrast with recent findings from other temperate woodland-dominated regions in eastern Australia where losses in bird populations have been documented. However, they parallel other investigations such as in central New South Wales. These similarities among, and differences between, studies suggest regional differences in temporal patterns in bird population dynamics. Many of the observed changes in reporting rates were positive and they provide hope that forecast future losses of a large proportion of existing temperate woodland bird assemblages in south-eastern Australia may not be realised uniformly in all regions.  相似文献   

12.
The influence of environmental factors on species richness and species composition may be manifested at different spatial levels. Exploring these relationships is important to understand at which spatial scales certain species and organism groups become sensitive to fragmentation and changes in habitat quality. At different spatial scales we evaluated the potential influence of 45 factors (multiple regression, PCA) on saproxylic oak beetles in 21 smaller broadleaved Swedish forests of conservation importance (woodland key habitats, WKH). Local amount of dead wood in forests is often assumed to be important, but two landscape variables, area of oak dominated woodland key habitats within 1 km of sites and regional amount of dead oak wood, were the main (and strong) predictors of variation in local species richness of oak beetles. The result was similar for red-listed beetles associated with oak. Species composition of the beetles was also best predicted by area of oak woodland key habitat within 1 km, with canopy closure as the second predictor. Despite suitable local quality of the woodland key habitats, the density of such habitat patches may in many areas be too low for long-term protection of saproxylic beetles associated with broadleaved temperate forests. Landscapes with many clustered woodland key habitats rich in oak should have high priority for conservation of saproxylic oak beetles.  相似文献   

13.
三川河流域农地土壤肥力的评价与调控   总被引:2,自引:0,他引:2       下载免费PDF全文
三川河流域属于国家8个水土保持重点治理区之一,随着治理的进展和农林牧业的发展,对耕地土壤的要求也越来越高。本文在对流域内不同耕地土壤肥力调查与测定的基础上,采用主成分分析(PCA),评价了不同类型农耕地的肥力状况,并划分了农地的类型,为不同类型农地土壤肥力的调控和农业发展,提供了科学依据。  相似文献   

14.
Traditionally, nature reserves have been centered mainly around areas that are important for vertebrate diversity. This practice has not gone unchallenged and may be a suboptimal choice for overall conservation planning. To investigate this problem, we sampled butterfly species richness in a nature reserve in north eastern Greece that was originally established for the protection of birds of prey. Patterns of butterfly species richness and abundance were investigated by means of transect walks across a range of the seven predominant habitat types (wet and dry meadow, pine, oak and mixed forest, grazed, and agricultural land). Data analysis, including ANOVA and DCA (detrended correspondence analysis), revealed that the main gradients in butterfly species richness (low to high) were from sites dominated by the pine forest matrix of the core areas of the reserve, to peripheral sites in landscapes of mixed or oak forest, and from sites with little human impact to more disturbed areas with high grazing pressure. Species of conservation interest were concentrated at sites of low human impact. Ten of them are endemic to Europe and/or threatened in Europe. In this respect, the most important species are Lycaena ottomanus, Thymelicus acteon, and Pseudophilotes vicrama which are declining all over Europe. Our results suggest that (1) traditional agricultural practices in areas surrounded by forest can be considered as important management tools in butterfly conservation, (2) highest butterfly species richness is found in the periphery of the reserve rather than in the core areas, and (3) for butterfly conservation the zones surrounding the strictly protected areas are equally important as the core areas.  相似文献   

15.
Stipitate hydnoid fungi (specifically members of the genera Bankera, Hydnellum, Phellodon, Sarcodon) have become the focus of increasing conservation concern, particularly following the detection of widespread declines in abundance. To assess their status in Scotland, 103 field surveys were undertaken, including searches of 50 of the 77 native pinewood sites, traversing a total of 902 km. Hydnoid fungi were encountered on 30 of the searches (29%), primarily in eastern regions of Scotland. A maximum of 8 species was recorded on a single search, 11 species being encountered in total. Of 22 plantation sites surveyed, 11 were found to contain populations of hydnoid fungi. Four species were relatively widespread, both in native woodlands and plantations: Bankera fuligineoalba, Hydnellum peckii, Phellodon tomentosum, and Sarcodon imbricatus. All species tended to be associated with particular microsites, especially riverbanks, tracksides or areas of exposed mineral soil; median values for percentage bare ground cover surrounding each sporome were generally above 50%. Median values for diameter at breast height (dbh) of associated trees were in the range 20-50 cm for all species. Data from the field surveys were pooled with previous records to assess the number of hydnoid species recorded for each native pine woodland. When examined by regression, a positive relationship was recorded between the number of species and woodland area (r2=0.69, P<0.001, n=50). To assess the occurrence of declines, the number of 10 km gridsquares for each species was compared using records made pre- and post-1970. These data provided evidence for declines in only four of the 17 species considered. However, 12 species are threatened with extinction according to the IUCN Red List criteria, owing to their restricted patterns of distribution. The implications of these results for the conservation of hydnoid fungi in Scotland are discussed.  相似文献   

16.
Five types of British woodland are particularly important for habitat conservation, namely; relicts of medieval wood-pasture management; ‘native’ pine and birch woods in the Scottish Highlands; some coppices on ancient woodland sites; woods on inaccessible sites; and woods with a long period of natural structural development. The case for these priorities rests on the concepts of non-recreatability and past-naturalness, which are discussed. Together these woods form no more than 20% of existing woodland. Comparison with woodlands and forestry practice in Czechoslovakia and France shows how much the definition of priorities depends on the particular climate, woodland history and current forestry practices of Britain. The same concepts can apply to other semi-natural habitats in some circumstances.  相似文献   

17.
The federally endangered Karner blue butterfly (Lycaeides samuelis) is the focal species for a conservation plan designed to create and maintain barrens habitats. We investigated whether habitat management for Karner blue butterflies influences avian community structure at Fort McCoy Military Installation in Wisconsin, USA. From 2007 through 2009 breeding bird point count and habitat characteristic data were collected at 186 sample points in five habitat types including two remnant barrens types, barrens habitat restored from woodland and managed specifically for the Karner blue butterfly, and two woodland habitat types. Although the bird community of managed barrens was not identical to the communities of remnant barrens, the Field Sparrow (Spizella pusilla), a species of conservation concern, and sparse canopy associated bird species, such as the Baltimore Oriole (Icterus galbula) and Eastern Bluebird (Sialia sialis) were predicted to occupy managed barrens and remnant barrens in similar proportions. Adjacent habitat was the most influential factor in determining the community of bird species using the managed barrens. In Wisconsin, and likely throughout the range of the Karner blue butterfly, management for the butterfly creates habitat that attracts a bird community similar to that of remnant barrens, and benefits several avian species of conservation concern. Additionally, the landscape context surrounding the managed habitat influences avian community composition. Managed barrens that are adjacent to remnant barrens, rather than adjacent to woodland habitats, have the highest potential for conserving barrens breeding birds.  相似文献   

18.
三川河流域属于国家8个水土保持重点治理区之一,随着治理的进展和农林牧业的发展,对耕地土壤的要求也越来越高。本文在对流域内不同耕地土壤肥力调查与测定的基础上,采用主成分分析(PCA),评价了不同类型农耕地的肥力状况,并划分了农地的类型,为不同类型农地土壤肥力的调控和农业发展,提供了科学依据。  相似文献   

19.
干旱、半干旱区的林地在保护国土、改善生态环境、维护生态平衡、拓宽人类活动空间、优化生存环境质量等方面起到了重要作用;尤其是在生态失衡,环境遭到破坏的荒漠化发生地区,以某种特殊目的营建起的农防林、水土保持林、水源涵养林等既是农牧业的人工防护屏障,又是整个农业生态系统的骨架;但是同时也讨论由于过度放牧、樵采和垦荒等破坏植被后导致的沙化,使林地成为沙源地的特殊情况。  相似文献   

20.
Determining the habitat requirements of a species is fundamental to effective conservation, particularly if the species is declining in areas where its habitat is being modified. Multi-scaled investigations of habitat use are essential because different selection processes may operate at different scales. I examined the habitat use of a declining woodland passerine, the rufous treecreeper (Climacteris rufa), at three spatial scales (landscape, woodland and territory) in the wheatbelt of Western Australia. Preferential habitat use was exhibited at all scales. At the landscape scale, wandoo (Eucalyptus wandoo) woodland was used at a significantly greater rate than three other common vegetation types. Territory use within woodlands was positively related to the density of hollow-bearing logs, the density of nest sites, and tree age. Within an individual territory, nest sites (hollows) were favoured if they had a spout angle of ?50° to the horizontal and an entrance size of between 5 and 10 cm. The rufous treecreeper preferentially used habitat with traits characteristic of old-growth wandoo woodland. Degradation of wandoo through habitat modification (e.g. grazing, logging, fire and removal of deadwood) represents a significant threat to the persistence of treecreepers.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号