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1.
While urban ecology is an expanding field of study, some natural areas within the urban environment remain under-examined. These include naturally regenerating forest communities adjacent to urban interstates. In addition, the status of interstate soils and their relationships with the community composition of forested interstate verges has received little ecological study. The purpose of this study was to examine variation in soil conditions along forested interstate corridors in Louisville, KY and to explore the extent to which soil characteristics (e.g., bulk density, pH) and heavy metals (e.g., Pb, Zn) vary with respect to three factors: interstate (e.g., traffic density), surrounding urban environment (e.g., industrial land use), and interstate construction legacies. Additionally, we explored the relationships between several edaphic factors and woody vegetation structure in these forested verges. We found that the degree and direction of the slope of land towards the interstate and the distance to the interstate pavement were strong determinants of soil characteristics and heavy metal concentrations, suggesting that the movement of de-icing salts, heavy metals, and other pollutants from the interstate was important in determining forest soil conditions along urban interstates. Since within our study area these highways did not extend into rural lands, variation in urban land uses and cover within 26 km of the city center was not large enough to explain variation in soil characteristics or heavy metals, except for a positive correlation between chromium and surrounding industrial land use. We did find that past physical soil disturbance caused by interstate construction (e.g., imported fill) left an important legacy on soil characteristics, heavy metal retention, and woody plant growth patterns in forests adjacent to urban interstates. The legacy of interstate construction on the current forest community structure (e.g., lower species richness) and the future forest (e.g., reduced tree regeneration) may further alter ecosystem productivity and ecosystem services provided by these forests and their soils.  相似文献   

2.
Urbanization threatens biodiversity, yet the number and scope of studies on urban arthropod biodiversity are relatively limited. We sampled ant communities in three urban habitats (forest remnants, community gardens, vacant lots) in Detroit and Toledo, USA, to compare species richness, abundance, and species composition. We measured 24 site characteristics to examine relationships between richness and composition and habitat patch size, vegetation, and urban features. Ant richness was higher in forests (26) than in gardens (14) and intermediate in vacant lots (20). Ant richness in gardens and vacant lots negatively correlated with abundance of an exotic ant species (Tetramorium caespitum); thus this ant may affect native ant richness in urban habitats. Ant composition differed with habitat type, and abundance was lowest in forests. Site characteristics varied with habitat type: forests were larger, had more woody plants, higher woody plant richness, more branches, and leaf litter whereas lots and gardens had more concrete and buildings. Vacant lots had taller herbaceous vegetation, and gardens had higher forb richness, density, and more bare ground. Differences in vegetation did not correlate with ant richness, but several vegetation factors (e.g. patch size, number and size of trees, leaf litter, and amount of concrete and buildings) correlated with differences in ant species composition. Additional factors relating to soil, nests, or microclimatic factors may also be important for urban ant communities. Implications for biodiversity conservation in urban ecosystems are discussed.  相似文献   

3.
We evaluated the richness, composition and abundance of bird communities in three urban forests of Mediterranean France during winter and spring. The urban forests differed in size, composition, structure, age of vegetation, and location relative to the city centre. Estimated species richness across all three urban forest parks was 45 species. Twenty six (26) species were recorded in both winter and spring, whereas ten species were recorded only in spring, and six were recorded only in winter. Distribution, turnover, and type of bird foraging guild were related to characteristics of each urban forest and season. During spring migration, more species were recorded in sampling units (250?×?250 m) within the largest and most natural urban forest located in the outskirts of Montpellier, whereas during winter, more species were recorded in the most urbanized park (i.e., a botanical garden dominated by exotic vegetation), which was located in the city centre. Insectivorous birds were more abundant in winter, whereas seedeaters associated with wooded habitats were recorded more frequently in spring. Our results suggested that different kinds of urban forests are important modulators of urban bird communities and they are necessary to maintain the diversity of migratory and resident birds as well as increasing the environmental quality of urban areas.  相似文献   

4.
Invasive species have been causing important and irreversible impacts to native species and communities of ecosystems. They distort ecosystem functions by degrading forest lands, wetlands, and agricultural habitats and replace the native vegetation and reduce biodiversity, forest productivity, and suitable wildlife habitat. To address disturbances caused by invasive species occurrence, further information is needed regarding the occurrence, extent, and dispersal of invasive species and how land use may increase the spread of these species. The objective of this study was to find the frequency and dominance of three invasive species common to riparian areas of east Alabama: Ligustrum sinense (Chinese privet), Elaeagnus pungens (silverthorn), and Triadica sebifera (Chinese tallow tree). Surveys of these species in riparian forests in and around Auburn, Alabama were conducted to show the relative extent of these shrubs and their relation to urban land use. It was expected to see the highest levels of invasive species in the city center with decreasing levels radiating outward into rural areas. Another objective was how urban land use may affect the presence-absence and prevalence of these non-native plant species within study sites. The results showed that around the city center and suburban lands, cover of both Chinese privet and silverthorn tended to increase. In contrast, Chinese tallow tree density percent cover showed an opposite trend with landscapes close to city center often having slightly less cover. This study shows that urban land use may be an important association with distribution of invasive plant species.  相似文献   

5.
Changes in riparian woody plant assemblages are anticipated in the southeastern United States due to increases in urbanization rates. Because riparian forests serve important roles in maintaining water quality and biodiversity, understanding how they respond to urbanization is crucial. The objective of this study was to examine forest structure and woody vegetation diversity indices of riparian communities in response to an urbanization gradient in West Georgia, USA. Measures of forest structure and diversity were compared to measures of urbanization and land cover. Although Liquidambar styracifluaand Quercus nigrawere dominant species in the forest stand and regeneration layer for all riparian communities, the invasive, non-native shrub Ligustrum sinense was the most dominant species observed in the regeneration layer for urban, developing, and agriculture communities. The proportion of non-native species in the forest stand and regeneration layer decreased and Shannon diversity of the regeneration layer increased with increasing distance from the urban center. Shifts in diversity indicate that anthropogenic disturbance may subdue the ability of diverse communities to resist non-native plant invasions.  相似文献   

6.
Plant diversity and composition in urban parks is determined by socio-economics, environmental, and ecological drivers. These drivers give rise to urban spaces with unique compositions of flora, consisting of planted and spontaneous species. The present study aimed to determine the contribution of native and exotic species in urban parks of a Latin American city, and to assess the related role of park area, age and socio-economic status. We also evaluated administration type (public or private) and the effect of environmental factors on plant richness. We hypothesized that the composition of park vegetation differs according to urban-rural gradient. To determine flora composition, two transects (100 m long by 1–3 m wide) per park were selected in 49 parks. In each of these, we identified all the vascular plants found (woody and herbs, planted and spontaneous), which were then classified as native or exotic. We conducted ANCOVAs in order to determine the effect of five independent variables and one factor, on native and exotic plant richness. Of 550 recorded species, 16.2% were native and 83.8% exotic. Number of plant species per park varied between 42 and 146. The parks are known urban habitats containing the highest planted and spontaneously occurring exotic diversity in the city of Santiago, contrasting with other types of habitats. Likewise, parks in Santiago are habitats with low levels of planted and spontaneously occurring native diversity, compared to the parks of Europe, America North and Asia. Ours results show that park area and age affected native plant richness, while exotic plant richness was determined only by park age. We rejected all other possible drivers. Finally, according to the low frequency of native species, we propose that Santiago’s parks could be gradually reoriented towards ex-situ conservation of native plants.  相似文献   

7.
Urban forests have garnered increasing attention as providers of an array of beneficial ecosystem services. However, urban forest ecosystems are highly complex and heterogeneous systems whose structure are shaped by interacting social and ecological processes. Approaches to reliably identify and differentiate these processes could be valuable for addressing complexity and reducing uncertainty in decision-making in urban forestry. The purpose of this study is to identify and quantify a range of social and ecological drivers of urban forest species composition, distribution, and diversity. This was done using hierarchical cluster analysis and discriminant analysis with empirical plot data describing the tree species composition in Toronto, Canada. Tree density and imperviousness were by far the most influential drivers of species composition. Increasing imperviousness saw not just reduced tree density but a decline in native species abundance. Additionally, single-detached housing, homeownership, and income were closely associated and explained higher tree densities and abundances of native species. However, income had a lower than expected influence on urban forest species composition given its importance in canopy cover research. Continuous forest patches were highly distinct compared to the remainder of the urban landscape, which highlights the ecological distinctiveness of residual forests within cities and lends support to their conservation. Increasing the understanding of social and ecological drivers of tree species composition, distribution, and diversity within cities is an integral part of urban forest ecosystem classification, which can be a valuable decision-support tool for ecosystem-based management in urban forestry.  相似文献   

8.
The aim of this study was to analyse the spatial distribution of vascular plants along a 21-kilometre rural–urban–rural transect in the city of Tampere, Finland. The study emphasised the distribution of native and non-native species, both in absolute numbers and proportionally. The observed differences are explained by the share of forest land, the number of detached houses, distance from the city centre, and human population. Non-natives showed the highest values in suburban areas. Still, the difference in number of non-natives between suburban and central areas was quite small. In the city of Tampere, there are not continuous large areas devoid of vegetation. The number of native species remained high until the urban core and natives dominated in the rural-type areas of the city. However, there was not a great difference in the number of native species between rural and suburban areas. In the suburban areas, the detached houses and block-of-flats have little effect on the general vegetation. Proportionally, the share of natives decreases in line with the urban traits of the city. Urbanisation therefore affects native species in Finland. Overall, the characteristic features of a Finnish city, such as dispersed urban structure, small population, late urbanisation, abundant natural vegetation (forest) and the qualities of Finnish forests, guarantee the continuing diversity of urban vascular plants.  相似文献   

9.
Lv  Hailiang  Yang  Yanbo  Zhang  Dan  Du  Hongju  Zhang  Jianyu  Wang  Wenjie  He  Xingyuan 《Urban Ecosystems》2019,22(4):631-642

To maximize the ecological services of urban forests, a better understanding of the effects of urbanization on urban forest characteristics, landscape metrics, and their associations is needed for landscape-related regulations in space-limited green infrastructure of metropolitan regions. In this study, Harbin, a typical fast-growing provincial-capital city in Northeast China, is used as a case study. Based on remote sensing images, field surveys, and correlation and variation partitioning analyses, we conclude that landscape characteristics and forest attributes have large variations among different urbanization intensity (UI) regions. Forest patch density (PD), landscape shape index, woody plants species richness, and the Shannon–Wiener index (H′) increased linearly, while stem section area and tree height decreased linearly with the increasing of UIs. UI had a greater influence on tree size and forest community attributes than the forest landscape pattern. Accordingly, any landscape regulation on forest attributes should be implemented according to UIs. In addition, Euclidean nearest neighbor distance(ENN-MN), mean perimeter-area ratio (PARA-MN), fractal dimension index(FRAC-MN), and PD could probably indicate forest attributes the most, e.g., the increase of PARA-MN may be accompanied with taller trees in low and heavy UI regions, but lower woody plants species evenness in low and medium UI regions. More diversified woody plants species, and afforested areas should be advocated in a low UI region, while in a heavy UI region, the conservation of large trees should be implemented. Our results highlight that the implementation of urban forest management should vary according to different urbanization regions to maximize ecological services.

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10.
We analyzed how urbanization in a desert ecosystem affects avian distribution at two distinct scales. At the regional level, we compared how urban land use configuration, relative to its surrounding agricultural fields and desert, affected the distribution of native and exotic species. While exotic species are isolated to the city; native species actively utilize the entire region, even occurring at higher densities in the city than in some areas of the desert. We also used this approach to compare four foraging guilds of birds: granivores, nectivores, omnivores, and insectivores. Granivores occurred mostly in agricultural fields and in the surrounding urban areas. Nectivores and omnivores occurred throughout the region, but mostly within the city. In contrast, insectivores occurred mostly in the desert. At a more local scale, we tested how the abundance of native species, exotics species and the foraging guilds of birds responded to vegetation cover measured at varying spatial scales (0.1 km–10 km). Bird guilds responded to vegetation at different scales, depending on the association between their life history and vegetation. Granivore abundance was most strongly correlated with vegetation at relatively fine spatial scales, followed by nectivores and omnivores at larger scales; whereas insectivores did not correlate with vegetation at any scale. Exotic and native species showed strikingly opposite trends in their association with vegetation. Native species showed the best fit at the smallest spatial scale and became insignificant at larger scales, whereas the highest correlation of exotic species with vegetation was at moderate to larger scales. While guild relationship with vegetation appears straightforward, the differences between exotic and native birds may indicate a complex response to environmental factors. Possibly, native species are more sensitive than exotics on vegetation abundance for food and shelter, which in the desert is highly variable depending on water availability. In contrast, exotic species, tightly connected to the urban infrastructure, likely respond to the enhanced and homogenized resource abundance characteristic of desert cities. Our results suggest that relationships between birds and vegetation may bear important information that can be revealed when considering smaller class levels than total species diversity.  相似文献   

11.
Isopod assemblages were studied in Budapest, capital of Hungary. The analyses of literary and field data revealed a high species richness (28 species), compared to the total species number (57) in Hungary. Habitats characteristics for the city were categorized as native forests, urban forests, gardens of Buda, gardens of Pest, public parks, densely built-up areas and botanical gardens. We hypothesized that isolated and diverse habitat patches in the city matrix of Budapest support the introduction and establishment of exotic species and the survival of native ones. The composition of assemblages varied among sampling sites, but were characteristic for the biotope categories. We concluded that forests, parks and gardens play an important role in the survival of native isopod populations. Species numbers were highest in the gardens of Buda and in the botanical gardens (both 17 species). The overall presence of cosmopolitan and disturbance-tolerant species indicates an ongoing homogenization process.  相似文献   

12.
Exotic trees can sustain native birds in urban woodlands   总被引:2,自引:1,他引:1  
Native landscaping has been proposed as a means of increasing native bird diversity and abundance in urban landscapes. However residents’ preferences for vegetation are such that exotic plants are often preferred over natives. We investigated the extent to which native birds foraged in three common native and three exotic tree species in mixed urban woodland during four seasons. We predicted that native birds would spend more time foraging in native trees, and that food resources provided by deciduous exotic trees would be more seasonal than those provided by non-deciduous natives. Native birds spent a lot of time foraging in two of the native tree species, but very little time in native red beech (Nothofagus fusca). They used exotic oak (Quercus robur) throughout the year, and sycamore (Acer pseudoplatanus) seasonally. Oak and European beech (Fagus sylvatica) were used by the largest number of species overall, because they attracted both native and exotic birds. With the exception of tree fuchsia (Fuschia excorticata), which produces large volumes of nectar followed by fruits, all tree species were sources of invertebrates for insectivorous feeding. Seasonality of use was high only in sycamore, indicating limited support for our second prediction. We show that being native doesn’t necessarily entail being a good food source for native birds, and popular landscaping exotic species, such as oak, provide foraging opportunities across all seasons.  相似文献   

13.
Woody vegetation and canopy fragmentation along a forest-to-urban gradient   总被引:9,自引:5,他引:4  
To identify patterns that can be used to predict vegetation and landscape characteristics in urban environments, we surveyed the species composition and size of woody plants, as well as the landscape structure of forest canopies, along a forest-to-urban gradient near Oxford, Ohio, USA. The gradient included six sites of increasingly urban land-use: a preserve, a recreational area, a golf course, a residential subdivision, apartment complexes, and a business district. We recorded species identity and stem diameter for all woody plants greater than 3 cm diameter at breast height (DBH) to examine the distribution of individual species as well as overall community composition. We used digitized aerial photographs to compare the spatial characteristics of the forest canopy at each site. We found predictable patterns in species diversity (Shannon index), spatial heterogeneity in species composition (mean percent dissimilarity), and all measures of patch fragmentation (canopy cover and patch number and size). There were clear differences in tree density and total basal area between forested sites and developed sites, but there was little resolution among developed sites. Species richness and average DBH showed no clear pattern, suggesting that landscaping preference largely determined these values. We present a modified version of an intermediate heterogeneity model that can be used to predict diversity patterns in urban areas. We discuss probable mechanisms that led to these patterns and the potential implications for animal communities in urban environments.  相似文献   

14.
Urban forests provide important ecosystem services. In terms of hydrological benefits, forest ecosystems in urban environments represent qualitative and quantitative filter for rainwater. We quantified the canopy interception in relation to urban forest stand structure and rainfall intensity in an urban transect of the mixed (upland) forest in the city centre, towards a riparian pine forest and a floodplain hardwood forest in the City of Ljubljana, Slovenia. Bulk precipitation in open areas and throughfall were measured with fixed rainfall collectors in each forest. Stemflow was estimated from a review of relevant literature. We found that canopy interception in selected urban forests was mainly affected by tree species composition and other stand structure variables, such as canopy cover and tree dimensions. Average annual canopy interception was highest in the mixed forest (18.0% of bulk precipitation), while the riparian pine forest had the lowest level (3.9% of bulk precipitation) and the floodplain hardwood forest had the intermediate level for interception (7.1% of bulk precipitation). The mixed forest exhibited the stand structure factors that contributed to the highest canopy interception among the studied forests: high assemblage of dominant coniferous trees, denser canopy cover and the highest growing stock. Furthermore, rainfall intensity has proven to be an important factor for the seasonal partitioning (comparing the leafed and leafless period) of canopy interception. A better understanding of precipitation interception processes in urban forests is needed to assist urban forest managing and planning, aiming at maximizing canopy interception for the mitigation of stormwater runoff and flooding in urbanized watershed.  相似文献   

15.
Seedling recruitment shapes tree communities, including those found in altered landscapes such as urban forests. However, little data exists on local- and broad-scale tree seed immigration and recruitment in these communities. Interspecific competition and seed predation are two major causes of recruitment failure for plants. In North American urban forests, these pressures may be exacerbated by an altered disturbance regime and prevalent invasive species combined with dense populations of rodents and browsers. Preliminary investigation in an urban forest on the eastern shore of Lake Erie indicated very low long-term tree seedling recruitment in the mature canopy stands. Our competing hypotheses were that seed establishment (habitat suitability) and seed limitations (seed availability) explained the tree recruitment failure. We tested seed establishment using field experiments (burning and vertebrate herbivore exclosures) and seed limitation by introducing native tree seeds. Moreover, we tested also seed limitation by examining local and regional seed input using seed traps. We found that seedling recruitment increased significantly with experimental reductions in predators and competitors, suggesting strong biotic establishment limitations in the urban forest. In addition, seed rain correlated significantly with immediately proximate parent plants, but no species arrived beyond what occurs within 50 m of the experimental plots. Essentially, then, the existing canopy species are not replacing themselves and extant seeds are not immigrating to replace them. At the patch scale, habitat quality, particularly seed predation and browsing, as well as competition from nonnative understory shrubs, constrained native tree recruitment in the urban forest. At the landscape scale, the evidence of poor long-term seed recruitment and the lack of long-distance seed input also suggest low native tree seed availability. The tree recruitment failure suggests that, in the absence of active management, this urban forest may eventually convert to an invasive-species dominated urban shrubland.  相似文献   

16.

Urban forests are valuable spaces for species conservation, protection of local biodiversity and provision of ecosystem services. However, they are also vulnerable to the impact of extreme climate events like hurricanes. Understanding how urban forests are responding to hurricane disturbances is crucial to improve their design, management, and resilience. Here we analyzed pre-and post-hurricane vegetation surveys in 52 residential yards in San Juan to assess urban forest responses after Hurricanes Irma and María impacted Puerto Rico in 2017. We used these surveys to compare vegetation structure and composition (including species-specific mortality and damage rates) and to quantify changes in the ecosystem services provided by these yards. We found that hurricane disturbances significantly altered the structure but not the composition of yard vegetation. We detected a 27% reduction and 31% mortality of standing stems, and a significant reduction in plants health. Yard species composition was dominated by non-native species and this trend did not change with hurricane disturbance. Changes in vegetation structure translated into substantial reductions in ecosystem services. Food provision, an important service provided by a large proportion of yards before the hurricane, reported the highest reduction (41.9%) while carbon storage was the service that changed the least (9%). Our combined results emphasize the key role played by residential yards providing ecosystem services in tropical cities and call for further efforts to manage private and public urban forests in ways that may ensure their resilience to mitigate extreme climate events, provide multiple ecosystem services, and promote long-term urban sustainability.

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17.
Leaf litter, by modifying microenvironmental conditions, can alter plant population distributions and is considered to be a major force in structuring many plant communities. Comparative studies of urban, suburban, and rural forests in the New York City (NYC) metropolitan area have identified numerous biotic and abiotic differences among these forests, including several involved in leaf litter decomposition. These differences in decomposition among the forests could result in differences in litter quantity on the forest floor and hence microenvironmental conditions and safe sites for germination of different plant species. We conducted a survey of forest floor leaf litter quantity in forests located along an urban-to-rural land-use gradient originating in urban NYC and extending to rural Connecticut. Mean litter depth, mass, and density increased significantly with increased distance of the forest from NYC.We also surveyed woody seedlings and compared the litter depth in which they naturally occurred to the mean litter depth of the surrounding forest. Seedlings of small-seeded species were much more likely to be located in litter shallower than mean forest litter depth than were seedlings of large-seeded species. Taken together, these results suggest that environmental changes associated with urbanization may have profound effects on long-term patterns of forest regeneration.  相似文献   

18.
There has been an increasing interest in urban forests and the levels of biodiversity they contain. Currently there are no spatially explicit maps of tree species richness in urban areas. This research tests and identifies GIS and remote sensing metrics (climate, area, productivity, three-dimensional structure) hypothesized to be associated with species richness in native forests and identifies methods that can be applied to predict and map tree species richness in cities. We quantified tree species richness, floristic composition, and structure in 28 1-ha plots in the city of Los Angeles. Climate and remote sensing metrics from high-resolution aerial imagery (10 cm), QuickBird (60 cm), Landsat (30 m), MODIS (250 m), and airborne lidar (2 m) were collected for each plot. There were 1208 individual stems and 108 trees identified to species. Species richness ranged from 2 to 31 species per ha and averaged 17 species per ha. Tree canopy cover from QuickBird explained the highest portion of variance (54%) in tree species richness followed by NDVI from Landsat (42%). Tree species richness can be higher in residential urban forests than native forests in the United States. Spatially explicit species richness maps at 1 ha can be created and tested for cities in order to identify both hotspots and coldspots of tree species richness and changes in species richness over time.  相似文献   

19.
Cities are systems that include natural and human-created components. When a city grows without proper planning, it tends to have low environmental quality. If improving environmental quality is intended, people’s opinion should be taken into account for a better acceptance of urban management decisions. In this study, we assessed people’s perception of trees by conducting a survey with a controlled sample of citizens from the city of Morelia (west-central Mexico). Citizens liked both native and exotic tree species and rejected mainly exotic ones. Preference for trees were related to tree attributes; such as size. Trees that dropped leaves or tended to fall were not liked. The most-mentioned tree-related benefits were oxygen supply and shade; the most mentioned tree-related damages were accidents and infrastructure damage. The majority of respondents preferred trees near houses to increase tree density. Also, most respondents preferred trees in green areas as well as close to their houses, as they consider that trees provide oxygen. The majority of the respondents thought more trees were needed in the city. In general, our results show that although people perceive that trees in urban areas can cause damages, they often show more interest for the benefits related to trees and consider there should be more trees in cities. We strongly suggest the development of studies that broaden our knowledge of citizen preferences in relation to urban vegetation, and that further policy making takes their perception into account when considering creating new urban green areas, regardless of their type or size.  相似文献   

20.
Urban areas are increasing in number, extent, and human population density worldwide. There is potential to mitigate negative impacts of urbanization to native pond-breeding amphibians by providing habitat in both remnant natural and constructed wetlands. This study examines amphibian use of potential breeding sites in natural and constructed ponds in a large metropolitan area to investigate habitat characteristics that are associated with successful breeding. I surveyed 62 ponds over three breeding seasons in Portland, Oregon, measuring eleven habitat characteristics that may influence their successful breeding: pond depth, nitrate level, aquatic refugia, aquatic vegetation, surrounding vegetation, pond permanence, presence of fish and of introduced bullfrogs, surrounding road density and forest cover, and whether they were constructed or remnant natural ponds. Five of the six native pond-breeding species that occur in the region were regularly found breeding in city ponds. Surrounding forest cover and amount of aquatic vegetation were highly associated with breeding, indicating that preserving and planting vegetation likely benefits urban amphibians. Non-native bullfrogs were not associated with native species richness. Surprisingly, whether a pond was natural or constructed was also only weakly associated with native species breeding, and the trend was towards higher presence for all species in constructed ponds. This indicates that novel, human-dominated areas can provide habitat for these species. Consideration of habitat characteristics associated with breeding success in urban pond management will likely benefit native amphibians in these rapidly expanding landscapes.  相似文献   

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