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1.
This study focused on a suite of vascular plant species (six herbs and two grasses) common to traditionally managed, species-rich grasslands in Western Norway. We assessed the suitability of two species transfer methods (seed sowing and soil seed bank) for restoration of species-rich grassland on a newly established road verge. We compared the species' frequencies one and three years after they were sown on a naked, newly created road verge with their frequencies in aboveground vegetation and soil seed banks of comparable, local grasslands. Species frequencies in the aboveground vegetation differed significantly from those in the seed banks. Moreover, the frequencies in the seed banks differed from those recorded one year after sowing, and the frequencies in the aboveground vegetation differed from those recorded three years after sowing. Avenula pubescens and Knautia arvensis, found in more than 25% of the aboveground grassland plots, did not germinate from any of the seed bank samples. Festuca rubra, Galium verum, Pimpinella saxifraga and Silene vulgaris were more frequent in the aboveground plots than in the seed bank samples. Pimpinella saxifraga, Galium verum and Lychnis viscaria emerged quite well both from sown seeds and from the seed bank. Avenula pubescens was frequent in the aboveground vegetation, but did not germinate from sown seeds. Six species established well from seeds, and most increased in frequency in the sown plots from the first to the third year. No species was found in the sown plots only, but three years after sowing, three species were more frequent in the sown plots than in the aboveground vegetation of donor grassland plots. Our fine-scale, point-to-point study demonstrates that different restoration methods produce widely differing species composition even when the donor material is identical. We propose that different substrates and a combination of establishment methods (sowing and hay transfer) are needed as supplements to seed banks to re-establish species-rich grassland.  相似文献   

2.
Although urban habitats contribute to the conservation of species diversity, urbanization has significantly reduced biodiversity by causing environmental changes such as habitat loss and fragmentation. Therefore, research on urban biodiversity studies has become increasingly important. Historical heritage sites are recognized as important habitats in remnant green spaces in urban areas. We aimed to evaluate the role of historical sites in conserving biodiversity in urban areas. As the land in these historical sites is not modified, they have the potential to conserve biodiversity through continued maintenance activities such as mowing and tree cutting. In Japan, Tamagawa-josui, a waterway that runs from west to east through the Tokyo megacity (35° 40′ N, 139° 25′ E), has been recognized as a civil engineering heritage landmark that preserves water utilization technology from the early modern period (1600s, Edo-era). The present study examined the relationships between plant diversity and green space in a historic site of a megacity (i.e., Tamagawa-josui) and determined the factors that influence plant diversity. Specifically, we examined the relationships between plant species indices (species richness and species compositions) and environmental factors (management, environmental conditions, and landscape factors). The present study analyzed spatial changes in the plant species composition in Tamagawa-josui. We demonstrated that tree canopy openness was positively correlated with plant species richness, and the increased disturbance associated with developing historical sites as urban parks was negatively correlated with native plant species richness. In addition, there was significant species turnover in the plant community from upstream to downstream in Tamagawa-josui, which could largely be explained by spatial factors. We demonstrated that historical sites can provide potential habitats for the conservation of the plant species diversity, which is based on the effectiveness of the management of their vegetation.  相似文献   

3.
Past land use is an important factor determining vegetation in temperate deciduous forests. Little is known about the long-term persistence of these impacts on vegetation but especially on the seed bank. This study assessed whether soil characteristics remain altered 1,600 years after human occupation and if this yielded persistent differences in forest plant communities and their seed bank in particular. Compiègne forest is located in northern-France and has a history of continuous forest cover since the end of Roman times. Twenty-four Gallo-Roman and 24 unoccupied sites were sampled and data were analysed using paired sample tests to investigate whether soil, vegetation and seed bank still differed significantly. The soil was persistently altered on the Gallo-Roman sites resulting in elevated phosphorus levels and pH (dependent on initial soil conditions) which translated into increased vegetation and seed bank species richness. Though spatially isolated, Gallo-Roman sites supported both a homogenized vegetation and seed bank. Vegetation differences were not the only driver behind seed bank differences. Similarity between vegetation and seed bank was low and the possibility existed that agricultural ruderals were introduced via the former land use. Ancient human occupation leaves a persistent trace on forest soil, vegetation and seed bank and appears to do so at least 1,600 years after the former occupation. The geochemical alterations created an entirely different habitat causing not only vegetation but also the seed bank to have altered and homogenized composition and characteristics. Seed bank differences likely persisted by the traditional forest management and altered forest environment.  相似文献   

4.
Andy Millard 《Landscape Ecology》2008,23(10):1231-1241
The species composition of semi-natural vegetation in urban areas is influenced by a diversity of factors operating at a variety of spatial scales. This study investigates relationships at the landscape scale between species numbers of semi-natural plant communities and variations in the nature of designated urban green space. Species’ records were obtained from a survey of tetrads (2 km × 2 km) across a contiguous central area of built-up landscape and nearby satellite settlements in the metropolitan borough of Leeds, northern England. Plant species were categorised into natives, archaeophytes, neophytes, casuals and conservation-designated species. The type and extent of designated urban green space within a tetrad was determined using GIS. There was more built-up and designated green space area in the central urban area than in the satellite settlements. However, this difference was not reflected statistically significantly in plant category species’ numbers. Numbers of native species correlated positively with areas of green space designated for relatively high nature conservation value. Neophytes and casuals correlated positively with semi-natural green space lacking rare native species or high native species richness but designated principally for local community accessibility. The value of such spaces and the importance of their appropriate management, not only for community benefits like individual physical health and mental well-being, but also for overall urban plant biodiversity, is highlighted.  相似文献   

5.
We studied the temporal variation of the soil seed banks in the urban lots of Santiago, Chile. As most of the plants that emerge from the seed banks in lots are also found in open habitats and are easily germinable, we hypothesize that the seed banks in lots are highly dynamic and short-lived, with the bank depleted every year during the germination season to be reloaded with new seeds during the next seed dispersal period. In each 20 lots for two year (2017 and 2018), 9 soil samples were collected. These samples were obtained from three sampling points randomly distributed across the plots. The seed bank was estimated by seed germination in soil samples placed in plastic trays. The samples of all the lots were stratified at 2 °C by 3 months before sowing. In order to record the seed persistence, soil of three lots watered in 2017 for six months were dried and maintained under dark and non-watered conditions until re-sowing in autumn 2018. To determine if the seeds present cold-associated germination triggers, soils of five lots were maintained under dark conditions for 3 months (soils without cold stratification) for comparison with soils with cold stratification of the same lots. The above-ground plants were recorded in all lots for both years. Forty plant species were recorded in soil bank. The total emerged seedling densities ranged between 7,944 (2017) to 3,700 seedlings m-2 (2018). Species per lot varied between 17 and 7 during 2017, and between 14 and 3 during 2018. In five lots, seedling densities were not statistically different between cold stratified soil at 2 ° C and non-stratified. In three lots with re-sown soil, seedling density of the first sowing (4,096 seedlings m-2) was significantly higher than second sowing (201 seedlings m-2). Thirty-seven plant species were recorded in the above-ground vegetation during 2017 and 42 species in 2018. Species frequency of the seed bank was positively correlated with species frequency of above-ground vegetation. Concluding, the bank is highly dynamic, short-lived, and is depleted every year during the germination season, which begins with effective rainfalls, would be reloaded with seeds during the seed dispersal period.  相似文献   

6.
Agricultural intensification has led to dramatic losses in biodiversity over the past several decades. Many studies have shown the effects of intensification on vegetation or soil communities at field or local scales. However, the functional significance of biodiversity may only appear at larger spatial and temporal scales, due to exchanges among local ecosystems throughout a landscape. To examine how patterns of biodiversity loss are reflected at larger spatial scales, plant and soil biodiversity and associated indicators of ecosystem functions were assessed in riparian areas over a 150 km2 agricultural landscape in the Sacramento Valley of California. Publicly-available GIS data were first used to classify and select sites over the range of soils, topography and plant community types. Representative sites from the landscape were sampled for soil physiochemical properties, as well as microbial, nematode, and plant communities. Higher agricultural intensification, based on field and landscape indices, was negatively correlated with richness and diversity of plant and soil taxa, and was related to indicators of ecosystem functions, such as increased soil nitrate and phosphorus loading, decreased riparian health ratings, and lower soil carbon, soil microbial biomass and soil food web structure. Both field- and landscape-scale factors played important roles in the measured losses. The study area was composed of a wide array of soils, vegetation, and land management, indicating that the observed trends transcended site-specific conditions.  相似文献   

7.
Urbanization is a permanent and still continuing expansion of human settlements and is responsible for dramatic changes of natural areas to urban areas. In traditional view, urbanization is often blamed for the loss of biodiversity and biotic homogenization of natural communities. However, for some species, urban areas, can represent suitable environment for life and even enable them to maintain stable and abundant populations. Urban ecosystems are not homogenous; within human settlements we can find several different habitats which can be occupied by species with different tolerance to certain aspects of urban life. This diversity can be exhibited by interhabitat changes in species richness, diversity and abundances of local communities. Here, we investigated biodiversity patterns in bird communities of two urban habitats, parks and cemeteries, in three Central European countries. Data on species richness, diversity and abundances of birds were collected from published papers as well as unpublished sources. Our analyses revealed that bird species richness was positively correlated with area and age of trees in both habitat types. There was however no significant relationship between species diversity and area in both habitat types. Moreover, species composition of bird communities significantly varied between cemeteries and parks with strong preference for one of habitat types in several species. Predominant occupancy of habitat type by certain species could be linked to interhabitat differences in vegetation structure, human behaviour and management. Interestingly, several bird species often recognised as urban avoiders were detected in surveyed cemeteries and parks.  相似文献   

8.
Urban vegetation has been proved to play an important role in mitigating the heat island effect. However, it is not clear how independent small-scale plant communities affected the microclimate. In this paper, the effects of fifteen plant communities on temperature and relative humidity were investigated from November 2010 to October 2011 in urban parks in subtropical Shenzhen City, China. The canopy density, canopy area, tree height and the background climate conditions under plant communities were measured. The effects of small-scale plant communities on temperature and relative humidity were the most significant at 1400–1500 h during the day. The temperature reduction and relative humidity increase due to small-scale plant communities were higher in summer, followed by autumn, spring and winter. As compared to the control open sites, the temperature reduction due to plant communities ranged from 2.14 °C to 5.15 °C, and the relative humidity increase ranged from 6.21% to 8.30%. We found that multilayer plant communities were the most effective in terms of their cooling and humidifying effect, while bamboo groves were the least effective. Regression results revealed that four factors, namely canopy density, canopy area, tree height and solar radiation, had significant influence on temperature reduction and relative humidity increase.  相似文献   

9.
The importance of biodiversity conservation is well recognized, and the loss of biodiversity is particularly evident in highly urbanized areas. On the other hand, green spaces inside cities, as parks, can provide a resource for maintaining and increasing biodiversity, especially for bird species. However, only a few studies have addressed the effects of vegetation structure and land use composition on different components of biodiversity.Here, we explored the response of bird community composition to environmental differences related to land use composition and vegetation structure in green spaces in the city of Beijing, China. We compared the values of taxonomic diversity, functional diversity and community evolutionary distinctiveness in breeding bird communities, among ten urban parks of the world's third most populous city. Variation partitioning analysis and generalized linear mixed models were used to explore the unique and shared effects of land use composition and vegetation structure on each biodiversity metric.Park size was not associated with the diversity of bird communities in Beijing. Land use composition was the best predictor of change in bird community composition, followed by vegetation structure at ground level and the intersection between land use and vegetation structure at tree level. Water coverage increased bird species richness, while the presence of large trees increased both taxonomic diversity and bird functional richness in urban parks. Finally, the presence of patches of deciduous trees showed a positive effect on the average score of evolutionary distinctiveness of bird communities. In conclusion, we highlight that different elements of the environment are supporting different components of bird community diversity.  相似文献   

10.
Artificially developed habitats in urban ecosystems, known as novel ecosystems, have recently been underscored in terms of increasing urban green cover. However, patterns of changes in species diversity and composition in novel ecosystems over time remain poorly understood, making it unclear whether all novel ecosystems contribute to urban biodiversity. Here, we assessed how plant species diversity and composition in developed habitats changed over the years since the development of habitats (years since development) using a space-for-time substitution approach in the megacity, Tokyo, Japan. We established multiple survey transects at each study site to investigate the plant species diversity and composition. Using the ordination regression-based approach, we found that the plant species composition in developed habitats changed over the years since development and became similar to that in remnant habitats after approximately 130 years. We also found that the diversity of native plant species did not change whereas that of exotic species decreased with the years since development. Our results demonstrate the importance of developing new habitats for conserving urban biodiversity, while highlighting that exotic species can easily establish in newly developed habitats. Given that remnant ecosystems in urban areas are degraded by urbanization, the time required for novel ecosystems to become similar to remnant ecosystems is essential for predicting and conserving future urban ecosystems.  相似文献   

11.
Promoting the plant diversity of urban green spaces is crucial to increase ecosystem services in urban areas. While introducing ornamental plants can enhance the biodiversity of green spaces it risks environmental impacts such as increasing emissions of biogenic volatile organic compounds (BVOCs) that are harmful to air quality and human health. The present study, taking Qingdao City as a case study, evaluated the plant diversity and BVOC emissions of urban green spaces and tried to find out a solution to increase biodiversity while reducing BVOC emissions. Results showed that: (1) the species diversity and phylogenetic diversity of trees in urban green spaces were 22% and 16% lower than rural forest of this region; (2) urban areas had higher BVOC emission intensity (2.6 g C m−2 yr−1) than their rural surroundings (2.1 g C m−2 yr−1); (3) introducing the selected 11 tree species will increase 15% and 11% of species diversity and phylogenetic diversity, respectively; and (4) the BVOC emissions from green spaces will more than triple by 2050, but a moderate introduction of the selected low-emitting trees species could reduce 34% of these emissions. The scheme of introducing low-emitting ornamental species leads to a win–win situation and also has implications for the sustainable green space management of other cities.  相似文献   

12.
The importance of the spatial as well as the temporal structure of habitat patches for urban biodiversity has been recognised, but rarely quantified. In dynamic environments the rate of habitat destruction and recreation (i.e. the landscape turnover rate), the minimum amount of potential habitat, its spatial configuration as well as the environmental conditions determining habitat quality are crucial factors for species occurrence. We analysed species responses to environmental parameters and to the spatio-temporal configuration of urban brownfield habitats in a multi-species approach (37 plant and 43 insect species). Species presence/absence data and soil parameters, site age, vegetation structure and landscape context were recorded by random stratified sampling at 133 study plots in industrial areas in the city of Bremen (Germany). Based on the field data, we predicted species occurrences by species distribution models using a multi-model inference approach. Predicted species communities were driven by successional age both at the scale of a single building lot and at the landscape scale. Minimum average succession time of brownfield habitats required to support all and especially regionally rare species depended on the proportion of available open space; the larger the potential habitat area the faster the acceptable turnover. Most plant, grasshopper, and leafhopper species modelled could be maintained at an intermediate turnover rate (mean age of 10–15 years) and a proportion of open sites of at least 40%. Our modelling approach provides the opportunity of inferring optimal spatio-temporal landscape configurations for urban conservation management from patch scale species-environment relationships. The results indicate that urban planning should incorporate land use dynamics into the management of urban biodiversity. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

13.
As the world’s population gets increasingly more urban, the preservation of urban green spaces becomes an important issue in the political agenda worldwide. These spaces may mitigate the negative environmental impacts of urbanisation and improve quality of life. Aiming to increase knowledge in urban biodiversity we compared the diversity of vascular plants and soil microbial communities (fungi and bacteria) in two contrasting typologies of urban green spaces (public gardens and remnant forests) in the city of Coimbra (Portugal). We found 252 taxa of vascular plants of which 58% were native and 42% exotic. Although overall diversity indices were similar in both typologies of green spaces, species richness and percentage cover of native taxa were significantly higher in forests than in gardens. Overall, plant communities in the two typologies of green spaces were distinct. We found high variability among gardens, which is consistent with vegetation in gardens being determined by man rather than by competitive or successional processes. Interestingly, the disparity between gardens and forests was also visible for both bacterial and fungal communities indicating an association between above and below-ground communities. We showed that, due to their origin, remnant forests harbour plant taxa with high conservation and ecological values. It also showed that gardens have higher percentage of exotic species, which led us to conclude that native plant species should be given more emphasis in these spaces. City planners should promote urban development by incorporating an ecological perspective into their management plans to enhance human health and global environmental quality.  相似文献   

14.
The woody plant communities found on residential properties constitute an integral component of cities’ green infrastructure and serve as a nexus between urban residents and the natural world. Despite this importance, residential landscapes are infrequently designed with principles of sustainability in mind, resulting in the extensive use of pesticides to suppress a diverse array of plant pests. In this study, we ask whether ecological theory can inform the sustainable design and management of woody plant communities on urban residential properties. The associational resistance and dilution effect hypotheses are analogous hypotheses, which posit that increasing biodiversity can inhibit the abundance of herbivores and pathogens, respectively. Importantly, theory suggests that it might not just be diversity that matters, but the right kind of diversity (i.e., community composition). Previous studies have demonstrated that herbivore abundance can be greater on native plants compared to exotic plants in residential landscapes. However, little is known regarding whether this translates into greater numbers of interventions to reduce damage associated with plant pests on native plants. To test these hypotheses, we utilized a multi-year, commercial plant health care program dataset. We examined, at the residential property scale, the relationships between woody plant diversity, the percentage of plants that were native, and pest management interventions. We found that the number of pest management interventions targeting phytophagous arthropods, but not plant pathogens, was negatively related to woody plant biodiversity. The percentage of native plants on a property had no relationship with the number of pest management interventions that occurred. Consequently, efforts to increase woody plant biodiversity in residential landscapes could result in increased phytophagous arthropod pest suppression, thereby reducing the need for pesticide applications and their associated adverse effects.  相似文献   

15.
Drivers of patterns in plant diversity remain poorly understood in tropical cities. Therefore, we investigated diversity within the tropical city of Sanya in Hainan Province of southern China by sampling one to three plots within 154 urban functional units (UFUs) based on six primary and 18 secondary UFUs. To measure diversity, we determined the number of vascular plants (species richness; SR) within each functional unit based on vegetation plots. We computed Faith's phylogenetic diversity (PDFaith) using a large megatree of plant life. To assess the potential drivers of SR and PDFaith, we performed multiple regressions using socioeconomic, biophysical, and vegetation management variables. The results showed significant differences in SR and PDFaith among the six primary UFUs. PDFaith of cultivated species was significantly higher than PDFaith of spontaneous species in all UFUs except in the wasteland area. Management measures were better predictors of SR and PDFaith than socioeconomic variables. The best predictor of SR and PDFaith of spontaneous species was the management of the urban green space. Our results provide clear guidelines for improved management strategies in Sanya, especially by showing how spontaneous and/or cultivated plant diversity can be encouraged depending on environmental, ecological, and cultural needs. Our work also adds to the presently scarce literature on drivers of urban plant diversity in tropical cities worldwide.  相似文献   

16.
There is increasing focus on designing liveable cities that promote walking. However, urban walking routes can expose people to adverse environmental conditions that reduce health, well-being and biodiversity. Our primary objective is to assess how urban form is associated with environmental quality, including biodiversity, for people moving through urban spaces. We assess a range of environmental conditions that influence human health and biodiversity (temperature, noise and particulate pollution) and biodiversity of three taxa (trees, butterflies and birds) along 700 m public walking routes embedded in 500 m x 500 m grid cells across three UK towns. Cells are selected using random stratification across an urbanisation intensity gradient. Walking routes in more built-up areas were noisier and hotter; noise levels further increased in areas with more industrial land-use and large roads. There was no evidence of vegetation mitigating noise or temperature, but there was some evidence that increased vegetation cover mitigated small particulate pollution. Walking routes in more built-up environments had lower butterfly, bird and native tree species richness, and reduced butterfly abundance. Large roads were associated with reduced bird species richness and increased noise was associated with reduced bird abundance. Most specific measures of vegetation in the surrounding matrix (median patch size, structural complexity at 1.5 m resolution) were not detectably associated with biodiversity along walking routes, indicating minimal beneficial spill-over. Increased garden cover in the surrounding matrix was associated with less abundant and less species-rich butterfly communities. Our results highlight considerable heterogeneity in the environmental quality of urban walking routes and pedestrians’ potential to experience biodiversity along these routes, driven by reduced quality in areas with more built cover. A greater focus is needed on mitigating adverse effects of specific features of the built environment (roads, industrial areas, noise) surrounding walking routes to enhance the co-benefits of more biodiversity and healthier conditions for pedestrians.  相似文献   

17.
Urbanization introduces uncertainties to the biodiversity of plant communities. The perception of biodiversity can be associated with positive mental health and well-being, but direct evidence is still insufficient. In this study, we collected data about plant biodiversity assessments from studies on urban forests in the literature of China’s national knowledge infrastructure. Records of the species amount, Shannon index, and Simpson index were extracted from 49 urban forest parks in 13 cities across mainland China from 2018 to 2021. A total of 1938 facial photos were obtained from microblogs with check-in locations at these parks in the Sina Microblog in 2020. Happy, sad, and neutral emotions and positive response index (PRI; happy minus sad) were rated and mapped for spatial distributions. The amount of species was distributed as a heterogeneous pattern for all plant types, and biodiversity was higher in the northern regions (e.g., ~55% in Qingdao and over 50% in Taiyuan) than in southern cities along the Yangtze River (e.g., ~35% in Huaihua and Changsha). Trees did not account for the association of biodiversity with emotional expressions. Smiles were elicited mostly in parks with more diverse shrubs (Shannon index: R=0.4335; P = 0.0029) and herbs (R=0.6162; P = 0.0008). Females showed more smiles than males (47% vs. 32%, respectively; F=39.15, P < 0.0001), and happy emotions tended to be higher in older visitors (senior vs. younger: 58% vs. 43%, respectively; F=2.72, P = 0.0280). Overall, we recommend visiting parks in northern cities of China for the benefit of evoking positive emotions through experiencing abundant undergrowth species. Female visitors would benefit more than males in the promotion of mental well-being by perceiving diverse shrubs and herbs in urban forest parks.  相似文献   

18.
Natural parks are comprised of preserved forested natural areas that are undergoing natural ecological processes. These areas can offer a refuge for local biodiversity and contribute substantially to ecosystem services in both rural areas with relatively low population densities, as well as high-density urban areas. Forested natural parks located in urban areas should experience more stressful environmental conditions than nearby rural areas, yet we know relatively little about how urbanization impacts tree communities within these important natural habitats. To better understand the impact of urbanization on forests, we investigated the species composition, abundance, and diversity of midstory and canopy trees as well as tree seedlings in urban and rural natural parks in and around Cleveland, Ohio. We found that both urban and rural natural parks have similar tree abundance, but midstory and canopy trees as well as tree seedling communities in the urban natural parks included higher abundances of stress-tolerant species compared to rural parks. In addition, this pattern was driven by changes in native tree species, as we observed low abundance of invasive species. More stress-resistant native species in urban areas include Quercus rubra and Prunus serotina, in contrast to rural natural parks which are dominated by Acer spp. and Fagus grandifolia. Lastly, we show that urban and rural natural parks have similar species diversity within plots, but we found higher variation in community composition among urban natural parks compared to among rural parks. Furthermore, Q. rubra and P. serotina were significantly larger in rural natural parks, indicating that both environmental stress and successional stage could drive compositional differences. Thus, we show that urbanization can have unexpected effects on plant community composition and diversity. Our study refutes the idea that these are degraded habitats, highlights the need to conserve them, and suggests that characterization of local variation in self-assembled urban tree communities will provide the most accurate picture of their management needs and potential ecosystem services.  相似文献   

19.
Biodiversity conservation in urban areas has become significant not only because of increasing human population in urban centers but also because it is one of the innovative ways to conserve biodiversity as suggested by various global environmental conventions. The present study was conducted with the purpose of assessing diversity and density of bird and woody species in some greenspaces of Delhi, the rapidly urbanizing capital of India. The landscape of Delhi consists of a broad spectrum of environments ranging from the city forests to highly modified artificial landscapes in certain parks. We assessed bird and woody vegetation in 20 m×50 m belt transects in each of the 19 randomly selected greenspaces of varying size. Results exhibit a negative relationship between the density of exotic woody species and bird diversity. Specifically, Prosopis juliflora – an exotic, which was the most abundant tree in our samples – exhibited a negative relationship with bird diversity. Principal component analysis (PCA) reveals that forest-preferring bird species increase with increasing greenspaces size, shrub diversity and shrub density. We conclude that maintaining larger greenspaces with high structural diversity may be effective in maintaining plant and bird diversity in the study area.  相似文献   

20.
In coastal southern California, natural riparian corridors occur in a landscape mosaic comprised of human land uses (mainly urban and suburban development) interspersed among undeveloped areas, primarily native shrublands. We asked, does the composition of the landscape surrounding a riparian survey point influence plant species distribution, community composition, or habitat structure? We expected, for example, that invasive non-native species might be more abundant as the amount of surrounding urbanization increased. We surveyed 137 points in riparian vegetation in Orange County, California, along an urbanization gradient. Using logistic regression we analyzed 79 individual plant species’ distributions, finding 20 negatively associated and 12 positively associated with the amount of development within a 1-km radius around the survey points, even after accounting for the effects of elevation. However, after summarizing plant community composition with Detrended Correspondence Analysis we observed that, overall, community composition was not statistically correlated with the amount of development surrounding a survey point once the association between development and elevation was taken into account. Non-native species were not particularly associated with increasing development, but instead were distributed throughout vegetation and urbanization gradients. However, the extent of the tree and herb layers (structural attributes) was associated with development, with the tree layer increasing and the herb layer decreasing as urbanization increased. Thus, although the degree of surrounding urbanization appears to influence the distribution of a number of individual plant species, overall composition of the community in our study system seemed relatively unaffected. Instead, we suggest that community composition reflected larger-scale environmental conditions, such as stream order and other variables associated with elevation, and/or regional-scale disturbances, such as historic grazing or enhanced atmospheric deposition of nitrogen.  相似文献   

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