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1.
We evaluated ground beetle diversity in relation to forest edge between an oak-hornbeam forest and adjacent herbaceous grassland. To test our hypothesis that the diversity of ground beetles was higher in the forest edge than the interior, pitfall trap samples were taken along two forest-grassland transects in northern Hungary. The diversity of ground beetles was significantly higher at the forest edge and in the grassland than in the forest interior. Ground beetle assemblages in the forest interior, forest edge and grassland could be separated from each other by ordination. Indicator species analysis detected five groups of species: habitat generalists, grassland-associated species, forest generalists, forest specialists, and edge-associated species. Rank correlation indicated leaf litter, herb, canopy cover, and prey abundance as the most important factors influencing carabid diversity. The high diversity of the forest edge resulted from the presence of edge-associated species and of species characteristic of adjacent habitats. Forest edges seem to play an important role in maintaining diversity. Serving as source habitats, edges also contribute to the recolonisation by ground beetles after habitat destruction or other disturbance in the adjacent habitats.  相似文献   

2.
Forest management practices can be detrimental to the long-term persistence of native species in exotic tree plantations. Knowledge of population recovery times post-harvest and dispersal capabilities of native species are critical to the development of spatially-explicit stand management plans that maximise biodiversity opportunities at a landscape scale. To quantify post-harvest recovery patterns we studied the relative capture rates of seven beetle species known to be sensitive to clearfell harvesting. A chronosequence sampling approach was implemented, with sampling along 580-m long edge gradients from the interior of multiple replicated mature stands of 26 years of age into adjacent regenerating stands of 1, 2, 4, 8, 16, and 26 years of age. Beetle capture rates were strongly affected by clearfell harvesting, however, population recovery of all species was possible within the timeframe of a single rotation when adjacent mature or closed-canopy stands were present. Recovery time was closely linked to the development of a closed canopy (8–16 years), with distinct differences in the responses of individual beetle taxa reflecting habitat preferences for open or closed forest. Such time-to-recovery analyses provide insights into temporal aspects of insect–plant–habitat interactions and can give forest managers better guidelines to maximise biodiversity opportunities at the landscape scale. Although the time to canopy closure provides a useful proxy for recolonisation by forest species, specific timeframes will vary biogeographically and are dependent on the original native vegetation context and species assemblages present. In addition, forest managers and public advocacy groups will need to make qualitative decisions about what biodiversity attributes should be conserved.  相似文献   

3.
In this study we compared ground beetles (Carabidae) from a range of different forest fragments along an urbanization gradient in Brussels, Belgium. We address the following questions: (i) How does the degree of urbanization in the surrounding habitat affect forest beetles, and does it interact with the effects of patch size and distance to forest edge? (ii) Do these factors have a different effect at the level of individual species, habitat affinity groups or total community? During 2002 we sampled 13 forest plots in 10 forest patches, ranging in size from 5.27 to 4383 ha. The beetles were captured using transects of pitfall traps from the edge to a distance of 100 m into each woodland and identified to species level. Effects of urbanization, forest size and forest edge were evaluated on total species number, abundance and habitat affinity groups and ten abundant, widespread model carabid species. Overall, the effects of urbanization, forest size and edge effects slightly influenced total species richness and abundance but appeared to have a major effect on ground beetle assemblages through species specific responses. More urbanized sites had significantly fewer forest specialists and more generalist species. Large forest fragments were favoured by forest specialist species while generalist species and species frequently associated with forest (forest generalists) dominated the smaller forests. Forest edges mainly harboured generalist species while forest specialist species were more frequent into the forests if the forest patches were large enough, otherwise they disappeared due to the destruction or impoverishment of their habitat. Our results show the importance of differentiating between habitat affinity, especially habitat generalists versus specialists, the latter having a higher value in nature conservation, and merely the quantity of species represented in human-dominated areas.  相似文献   

4.
We sampled the carabid beetles in 22 forests managed by six different silvicultural systems, defined by treatment and tree species composition: even-aged conifer, even-aged beech, even-aged oak, uneven-aged conifer, uneven-aged beech and group mixed (beech + conifer). In each of these forests, we placed pitfall traps in young, medium-aged and mature stands (3 stages). We evaluated the effect of treatment, tree species composition, silvicultural system, stage and habitat type (silvicultural system + stage) on indicators of community conservation value and ecological structure. The species composition and the ecological structure of carabid beetles of the managed stands were then compared to that of nine unmanaged stands (without tree exploitation). In the managed forests, species richness was highest in large young stands (3-10 years old) and in forests managed by even-aged systems (with large clear-cuts), mainly due to eurytopic and opportunist carabid species with high dispersal abilities. Oak and beech, uneven-aged, and mature stands were mainly inhabited by typical forest species, and even-aged conifer stands mainly by ubiquitous species. Several typical forest species recorded in unmanaged stands were lacking from the managed forests. Large scale clear-cutting allows open-habitat species to enter the forest, which increases the species richness at a landscape level but can disfavour typical forest species by competition. Long rotations should be implemented and more areas left unmanaged in Belgium, in order to help typical forest species to re-colonise managed forests.  相似文献   

5.
Two-age (deferment or leave tree) harvesting is used increasingly in even-aged forest management, but long-term responses of breeding avifauna to retention of residual canopy trees have not been investigated. Breeding bird surveys completed in 1994-1996 in two-age and clearcut harvests in the central Appalachian Mountains of West Virginia, USA allowed us to document long-term changes in these stands. In 2005 and 2006, we conducted point counts in mature unharvested forest stands and in 19-26 year-old clearcut and two-age harvests from the original study and in younger clearcut and two-age stands (6-10 years old). We found differences in breeding bird metrics among these five treatments and temporal differences in the original stands. Although early-successional species are typically absent from group selection cuts, they were almost as common in young two-age stands as clearcuts, supporting two-age harvests as an alternative to clearcutting. Although older harvests had lower species richness and diversity, they were beginning to provide habitat for some species of late-successional forest songbirds that were absent or uncommon in young harvests. Overall, late-successional forest-interior species were more flexible in their use of different seral stages; several species used both age classes and harvest types in addition to mature forest, which may reflect the lack of edges in our heavily-forested landscape. Consequently, two-age management provides habitat for a diverse group of species as these stands mature and may be an ecologically sustainable alternative to clearcutting in landscapes where brown-headed cowbirds (Molothrus ater) are uncommon.  相似文献   

6.
Saproxylic Coleoptera are diverse insects that depend on dead wood in some or all of their life stages. In even-aged boreal forest management, remnant habitats left as strips and patches contain most of the dead wood available in managed landscapes and are expected to act as refuges for mature forest species during the regeneration phase. However, use of remnant habitats by the saproxylic fauna has rarely been investigated. Our objective was to characterize the saproxylic beetle assemblages using clearcuts and forest remnants in western Québec, Canada, and to explore the effects of forest remnant stand characteristics on saproxylic beetle assemblages. We sampled both beetle adults and larvae, using Lindgren funnels and snag dissection, in five habitat locations (clearcuts, forest interiors of large patches, edges of large patches, small patches and cut-block separators) from three distinct landscapes. Adult saproxylic beetles (all feeding guilds combined) had significantly higher species richness and catch rates in small patches compared to forest interiors of large patches; the phloeophagous/xylophagous group had significantly higher species richness only. Small patches, cut-block separators and edges of large patches also had the highest snag density and basal area, increasing habitat for many saproxylic beetles. No significant differences in density of saproxylic larvae were found between habitat patches, but snag dissection nevertheless suggests that snags in forest remnants are used by comparable densities of insects. Saproxylic beetles appear to readily use habitat remnants in even-aged managed landscapes suggesting that forest remnants can insure the local persistence of these species, at least in the timeframe investigated in our study.  相似文献   

7.
Although natural disturbance has been widely adopted as a template for forest management that protects biodiversity, this hypothesis has not been adequately tested. We compared litter-dwelling arthropod assemblages (Coleoptera: Carabidae and Staphylinidae; Araneae) in aspen-dominated stands originating as clear-cuts or wildfires across three age classes (1-2, 14-15, and 28-29 years old) to test whether the post-harvest and post-fire assemblages converged following disturbances, and to compare faunal succession. These findings were compared to data about epigaeic arthropods in old and mature pyrogenic aspen stands (>70 years old) to determine whether diversity and community composition of arthropods from the younger age-classes approached what may have been typical pre-disturbance conditions. The resulting data-set of almost 27,000 arthropods and 230 species showed convergence in most taxa, and some general similarities between 28- and 29-year-old stands and old and mature stands. However, not all taxa responded similarly, and faunal succession following clear-cutting appeared to progress more rapidly than following wildfire. Rarefaction-estimated diversity was elevated in 1-2-year-old stands, compared to unharvested stands, reflecting a mix of closed-canopy and open-habitat species. Non-metric multi-dimensional scaling ordinations showed that samples from young wildfire disturbed stands (1-2 years old) included more variable assemblages than all other study sites, and contained species that may depend on unique post-fire habitat characteristics. The fauna of old and mature stands exhibited low diversity, but contained species with limited dispersal abilities, and species tied to old-growth habitats such as dead wood. Harvesting systems that do not allow adequate recovery following a first harvesting pass, or do not maintain microhabitat features associated with older fire-origin forests, may threaten persistence of some elements of boreal arthropod faunas.  相似文献   

8.
Patterns of biodiversity are influenced by habitat features at multiple spatial scales, yet few studies have used a multi-scale approach to examine ground-dwelling beetle diversity patterns. We trapped and quantified ground-dwelling beetle assemblages at two spatial scales: (1) microhabitat elements, represented by open ground, ground under trees and ground next to logs and (2) macrohabitat, represented by three vegetation types in a box-gum grassy woodland in south-eastern Australia. Species richness and evenness was highest at samples from under trees and lowest at samples in the open. At the macrohabitat scale, species richness and evenness did not differ among vegetation types. Assemblage composition was significantly different between trees, logs and open elements. Assemblage composition was different only between vegetation types with contrasting high and low shrub cover. Estimation of true species richness indicated assemblages at logs may have a higher number of species compared to trees and open elements, and implied greater spatial heterogeneity in assemblages at logs. Significant spatial autocorrelation in beetle assemblages was detected for logs at up to 400 m, but not for ground under trees or in the open. In agreement with previous studies, a mix of vegetation types at the macrohabitat scale is important for beetle conservation. Assemblage composition, however, appears to be more closely linked with habitat elements at the microhabitat scale, where logs support a high diversity of beetle species. This strongly supports the idea that restoring logs to box-gum grassy woodlands would be useful for increasing beetle species richness and assemblage heterogeneity.  相似文献   

9.
The long-term dynamics of plant communities remain poorly understood in isolated tropical forest fragments. Here we test the hypothesis that tropical tree assemblages in both small forest fragments and along forest edges of very large fragments are functionally much more similar to stands of secondary growth (5-65-yr old) than to core primary forest patches. The study was carried out in a severely fragmented landscape of the Brazilian Atlantic forest. Nine functional attributes of tree assemblages were quantified by sampling all trees (DBH ? 10 cm) within 75 plots of 0.1 ha distributed in four forest habitats: small forest fragments (3.4-79.6 ha), forest edges, second-growth patches, and primary forest interior areas within a large forest fragment (3500 ha). These habitats were markedly different in terms of tree species richness, and in the proportion of pioneer, large-seeded, and emergent species. Age of second-growth stands explained between 31.4% and 88.2% of the variation in the functional attributes of tree assemblages in this habitat. As expected, most traits associated with forest edges and small forest fragments fell within the range shown by early (<25-yr old) and intermediate-aged secondary forest stands (25-45-yr old). In contrast to habitat type, tree assemblage attributes were not affected by vegetation type, soil type and the spatial location of plots. An ordination analysis documented a striking floristic drift in edge-affected habitats. Our results suggest that conservation policy guidelines will fail to protect aging, hyper-fragmented landscapes from drastic impoverishment if the remaining forest patches are heavily dominated by edge habitat.  相似文献   

10.
Increasing demands for firewood owing to rising energy costs have accelerated discussions about the amount of dead wood needed for conservation. A sharp increase in dead wood caused by bark beetles in a German national park provides lessons for management of commercial and protected forests. We investigated the effects of dead wood due to bark beetle infestation as well as tree senility on abundance and richness of saproxylic species of beetles. Increasing amounts of spruce dead wood and opening of the canopy by bark beetles had positive effects on the abundance of host-generalist, conifer-specialist, and red-listed saproxylic beetles. Broadleaf specialists were positively associated with the amount of broadleaf dead wood and negatively associated with canopy openness. Gradient analysis of beetle assemblages revealed two major environmental axes: canopy openness and amount of dead wood. We found a threshold for community divergence at a canopy openness of 23% (confidence interval CI: 11-49) and at an amount of dead wood of 64 m3 ha−1 (CI: 35-160). Critically endangered species served as indicators of dense and open forests, but only when the amount of dead wood was high. Our results suggest that, to maintain saproxylic beetle assemblages, the amount of dead wood in commercial montane forests (at present ≈15 m3 ha−1) needs to be tripled, with a focus on broadleaf wood in dense stands and spruce wood in open stands. For large protected areas in Europe, our data suggest that bark beetle infestation and senescence without active forest management improves habitat conditions for saproxylic beetles.  相似文献   

11.
Several insect groups have adapted to fire cycles in boreal forests, and can efficiently use new habitats created by fire. Our study aimed at producing a first characterization of post-fire Coleoptera assemblages of black spruce forests of eastern North America. For two years, we sampled Coleoptera using flight-interception traps in burned stands of contrasting age and structure in a 5097-ha wildfire and in neighbouring unburned mature stands. More than 40 species were exclusively captured in burned stands. Time elapsed since fire and proximity of unburned forests were the most significant parameters affecting Coleoptera assemblages. Stand age and structure had limited effects on assemblage structure; the Scolytid Polygraphus rufipennis Kirby was the only common species to clearly favor older stands. Fire-associated Coleoptera assemblages found in our study area were clearly distinct from those found in similar unburned stands; we should thus be conservative in our management approach concerning recently burned stands.  相似文献   

12.
A key challenge for tropical conservation biologists is to assess how forest management practices affect biodiversity and associated ecosystem functions. Dung beetles (Scarabaeidae: Scarabaeinae) provide an ideal focal guild for such studies. We compared dung beetle assemblages and experimentally assessed rates of dung removal and seed burial in undisturbed forest, low-intensity selectively logged forest under sustainable forest management, and high-intensity logged forest, not under sustainable management in Malaysian Borneo. In total, 7923 individuals from 39 species of dung beetle were collected. There were no significant differences in abundance, biomass or diversity across sites. Species richness was significantly lower in the high-intensity logged sites. Beta diversity was low: of 35 species recorded in undisturbed forest sites, 32 were also captured in low-intensity sites and 29 in high-intensity sites. The environmental and vegetation variables measured had little influence on species composition. An average of 63–99% of dung was removed over 24 h. Mean dung and seed removal were significantly lower in the high-intensity logged sites. Dung removal rates were significantly and positively correlated with dung beetle species richness, but not with dung beetle biomass or abundance. However, the biomass of large-bodied, nocturnal dung beetles was positively correlated with dung removal. In contrast to previous studies, dung beetle biomass and abundance were not correlated with species richness, indicative of density compensation. Overall, dung beetle communities and associated ecosystem functions were robust to low-intensity but not high-intensity selective logging. These differences may be related to changes in the abundance and biomass of particular dung beetle species or guilds rather than community-wide measures of abundance and biomass, highlighting the need to move beyond simplistic biodiversity-ecosystem functioning correlations to understand the functional consequences of habitat modification in high-diversity ecosystems.  相似文献   

13.
New conservation-oriented forestry aims to maintain intact populations of forest organisms by improving the conservation value of managed forests and providing protected areas. We tested the conservation value of treatments of dead wood for assemblages of early successional saproxylic beetles. In nine areas in northern Sweden, we selected one clear-cut, one mature managed forest and one reserve. In 2001-2002, we placed three blocks of spruce logs, each containing control, burned and shaded logs and a high stump (“snag”) at each site. Saproxylic beetles emerging from the dead wood were collected using emergence traps and beetles flying close to it were collected using flight-intercept traps. After one year of exposure, assemblage composition was examined, with respect to nutritionally-defined functional groups, red-listed species and fire-favoured species. Experimental snags were most complementary to control logs, supporting different assemblages of cambium consumers and fungivores and supporting more red-listed individuals. Burned logs supported depauperate assemblages, particularly with respect to cambium consumers, while shading of logs affected assemblages of fungivores, but only on clear-cuts. Despite containing less dead wood, managed forests provided valuable habitat, supporting similar assemblages of saproxylic beetles to reserves. Most functional groups were less abundant on clear-cuts than in older forests, but fire-favoured species were more common on clear-cuts, suggesting that clear-cuts may support assemblages of species associated with natural disturbances, if suitable substrates are available. Utilization of logs by saproxylic beetles changes over time, so long-term monitoring of our experimental logs will determine their lifetime conservation value.  相似文献   

14.
Recent developments have highlighted the importance of forest amount at large spatial scales and of matrix quality for ecological processes in remnants. These developments, in turn, suggest the potential for reducing biodiversity loss through the maintenance of a high percentage of forest combined with sensitive management of anthropogenic areas. We conducted a multi-taxa survey to evaluate the potential for biodiversity maintenance in an Atlantic forest landscape that presented a favorable context from a theoretical perspective (high proportion of mature forest partly surrounded by structurally complex matrices). We sampled ferns, butterflies, frogs, lizards, bats, small mammals and birds in interiors and edges of large and small mature forest remnants and two matrices (second-growth forests and shade cacao plantations), as well as trees in interiors of small and large remnants. By considering richness, abundance and composition of forest specialists and generalists, we investigated the biodiversity value of matrix habitats (comparing them with interiors of large remnants for all groups except tree), and evaluated area (for all groups) and edge effects (for all groups except trees) in mature forest remnants. Our results suggest that in landscapes comprising high amounts of mature forest and low contrasting matrices: (1) shade cacao plantations and second-growth forests harbor an appreciable number of forest specialists; (2) most forest specialist assemblages are not affected by area or edge effects, while most generalist assemblages proliferate at edges of small remnants. Nevertheless, differences in tree assemblages, especially among smaller trees, suggest that observed patterns are unlikely to be stable over time.  相似文献   

15.
There are large numbers of records of uncommon beetles from exposed riverine sediments (ERS) (gravel, sand and silt shoals) in the UK. However, systematic surveys of their occurrence in relation to environmental controls are seldom undertaken. Data are presented here from a survey of 69 shingle ERS across England and Wales and used to establish which factors were important in constraining species assemblages. Over 480 species of Coleoptera were collected by a combination of pitfall trapping, hand searching and excavation techniques. A total of 81 species with conservation status of Vulnerable, Rare or Nationally Scarce were recorded during the work and this includes six species on the United Kingdom Biodiversity Action Plan (BAP) lists. A subset of 42 of these rare species can be classified as ERS specialists. The data were analysed using TWINSPAN, redundancy analysis (RDA), single factor ANOVA, general linear modelling (GLM) and correlation to examine the importance of selected environmental variables and their relationships with the species assemblages. The results indicate that: (i) ERS sites with large numbers of species that are either rare or exhibit strong fidelity to the sediments have a markedly western distribution in the UK and are found on unregulated rivers in Wales and a number of rivers in the south west of England, (ii) the type of substrate, habitat heterogeneity, the percentage of shade from trees, the percentage of fine sediments on the ERS, the amount of trampling and ERS size are important in determining invertebrate communities and (iii) ERS provide valuable and important habitats for rare beetles species in the UK. The importance of river regulation, engineering and trampling by stocking for ERS invertebrates is discussed.  相似文献   

16.
At the farm-scale, hedgerow, degraded hedgerow and fence field boundary types were sampled for overwintering carabid and staphylinid beetles. Distinct beetle assemblages were evident and the structural and botanical characteristics of the boundary types were good explanatory factors of the differences. Each field boundary type supported unique species not found elsewhere; nine species were contributed by hedgerows alone and six species each from degraded hedgerows and fences. Using a systematic complementary site selection method we determined that all field boundary types were of equal importance for full representation of carabid and staphylinid species at the farm-scale. Additionally, fence habitats supported generalist predators of crop pests in greatest densities, whilst degraded hedgerows were most valuable in providing refuge to species vulnerable to disturbance and habitat fragmentation. Contrary to expectation, woodland species were not more evident in hedgerows than either degraded boundaries or fence habitat. This study provides empirical evidence that some components of biodiversity and sustainable farming are best maintained by retaining habitat heterogeneity, including features currently considered of limited conservation value.  相似文献   

17.
The effort of boreal forest conservation has emphasised the preservation of old-growth forests while the role of young successional stages in maintaining biodiversity has remained largely unstudied. We compared the richness of beetle species and composition of species assemblages between managed and seminatural forests in five stages of forest succession. The sites were in boreal sub-xeric pine-dominated forests in eastern Finland. Seminatural study sites, especially the recently burned sites, were important habitats for threatened and near-threatened species. We propose that young stages of natural succession should be included in the network of protected forest areas. On the other hand, the composition of saproxylic species assemblages in seminatural forests differed from the assemblages in managed forests, indicating also the need to improve the forest management guidelines so that they better address the requirements of species protection. Regeneration methods applied should resemble or mimic the natural disturbances more closely.  相似文献   

18.
Reforestation has been suggested as a way to mitigate the effects of tropical rain forest loss. However, factors influencing the successful colonisation of biota into newly created rainforest are poorly understood. We assessed beetle species assemblages with flight interception traps, in sites undergoing rainforest restoration across the largely cleared landscape of the Atherton Tablelands in north-eastern Queensland, Australia. There were two levels of site age (2-4 years and 6-17 years) and two distances from intact rainforest (adjacent and >0.9 km), with six sites in each treatment, together with six reference sites in each of pasture and small rainforest remnants (n = 36 sites). Multivariate metrics were used to assess the restored sites’ relative similarity to pasture and rainforest, in terms of both physical habitat structure and beetle species composition within ten family groups. Older restoration sites were structurally most similar to rainforest. Older sites and those adjacent to rainforest had a more rainforest-like beetle species composition (without significant interaction). However, even the closer and older sites had a substantially lower abundance and richness of rainforest-associated beetles than did rainforest. Age effects were generally stronger than distance effects, with the latter appearing to be entirely driven by rare rainforest species. Beetle assemblage similarity to rainforest was more strongly correlated with structural similarity to rainforest than with age, except within older sites. The use of revegetation techniques which lead to more rainforest-like structural conditions appears to be of over-riding importance in catalysing the rapid acquisition of volant rainforest beetle assemblages in the initial stages of restoration.  相似文献   

19.
Despite the ubiquity of oribatid mites in soil and litter systems, and their importance in decomposition and nutrient cycling processes, little is known of the factors underlying the composition of their assemblages. Our objective was to address this by determining how oribatid assemblage composition changes by forest stand type. This work was done in and near a hardwood forest in southwestern Quebec, Canada. We sampled mites by collecting 1 L of litter and 170 cm3 of soil from four sites in each of four distinct habitat types: American beech stands, sugar maple stands, mixed deciduous stands and mixed conifer plantations. Samples were collected in July and September 2005, and June 2006, and over 6500 oribatid mites were collected and identified to species. Abundance and species richness differed between forest types: for abundance conifer>beech>maple>mixed deciduous while for species richness beech and conifer>maple>mixed deciduous. Ordination analyses revealed that conifer plantations and beech stands supported distinct assemblages, while there were some overlap in the assemblages found in maple stands and mixed deciduous stands. These data support the importance of aboveground plant communities in affecting the composition of oribatid assemblages even at local scales and provide insight into additional impacts that may be caused by shifts in plant species ranges due to global changes.  相似文献   

20.
We show how Chilean forest bird species richness, abundance and guild structure changes as a function of structural properties of forest stands. We surveyed bird assemblages in two old-growth (>200 years), two mid-successional (30-60 years), and two early-successional forest stands (4-20 years), from November 1999 to September 2000, on Chiloé Island, southern Chile (42°S). Birds were grouped into four habitat-use guilds: large-tree users, vertical-profile generalists, understory species, and shrub-users that occasionally use forests. We recorded a total of 24 bird species: 21 in old-growth, 14 in mid-successional and 16 in early-successional stands. Large-tree users and understory birds were most abundant in old-growth stands, vertical-profile generalists were common in both old-growth and mid-successional stands, and shrub-users were only common in early-successional stands. For nine bird species we found significant relationships between their local abundance and forest structural elements. Higher bird densities in old-growth forests were associated with greater availability of canopy emergent trees, snags, logs and understory bamboo cover in this habitat. Accordingly, bird species diversity in forest stands can be predicted by the presence of these structural elements, and forests should be managed to conserve structural elements that create favorable habitat for bird species in order to prevent future species losses due to logging practices.  相似文献   

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