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741.
坡度和雨强对喀斯特地区坡面产流产沙的影响   总被引:2,自引:0,他引:2  
利用径流小区观测法,分析了坡度和雨强对贵州喀斯特地区4种地类坡面产流产沙的影响。结果表明,随坡度的增大,各地类坡面产流产沙量并没有表现出一致增大或减小的趋势,它们在很大程度上受土地利用方式和土壤类型的制约;随最大30 min雨强(I)的增大,坡面的产流产沙量增大。坡度为13°时,坡耕地在各地类中的产流产沙量最小,随坡度增大逐渐超过其他地类;除13°径流小区外,经济林地(梨树)在各种坡度、雨强范围内的产流产沙量均为各地类中最少;水保林地(香樟)在各种情况下的产流量虽较大,但产沙量相对较小;裸地在观测条件下的产流产沙量均较大。  相似文献   
742.
刘易 《环境科学学报》2012,32(3):590-594
利用摇瓶序批式试验研究了好氧菌群对低浓度辛基酚的生物降解特性和群落特征.结果表明,在辛基酚初始浓度水平为200、100、50μg·L-1的条件下,一级反应动力学常数分别为0.131、0.219和0.431d-1,辛基酚浓度升高显示出一定的代谢抑制作用.在pH值为5~9的范围内,弱碱性条件(pH=8)最有利于辛基酚的生物降解.甲醇、葡萄糖、苯酚、酵母浸出物等有机添加物普遍可以改善辛基酚的生物代谢,其中,苯酚和酵母浸出物的促进效果最明显,在200μg·L-1的初始浓度下,辛基酚降解半衰期从5.3d分别降至3.2d和2.3d.与较高浓度烷基酚类污染物试验结果不同,实验过程中发现的主要优势菌以γ-proteobacteria、β-proteobacteria和Firmicutes为主.  相似文献   
743.
Abstract: Species’ assessments must frequently be derived from opportunistic observations made by volunteers (i.e., citizen scientists). Interpretation of the resulting data to estimate population trends is plagued with problems, including teasing apart genuine population trends from variations in observation effort. We devised a way to correct for annual variation in effort when estimating trends in occupancy (species distribution) from faunal or floral databases of opportunistic observations. First, for all surveyed sites, detection histories (i.e., strings of detection–nondetection records) are generated. Within‐season replicate surveys provide information on the detectability of an occupied site. Detectability directly represents observation effort; hence, estimating detectablity means correcting for observation effort. Second, site‐occupancy models are applied directly to the detection‐history data set (i.e., without aggregation by site and year) to estimate detectability and species distribution (occupancy, i.e., the true proportion of sites where a species occurs). Site‐occupancy models also provide unbiased estimators of components of distributional change (i.e., colonization and extinction rates). We illustrate our method with data from a large citizen‐science project in Switzerland in which field ornithologists record opportunistic observations. We analyzed data collected on four species: the widespread Kingfisher (Alcedo atthis) and Sparrowhawk (Accipiter nisus) and the scarce Rock Thrush (Monticola saxatilis) and Wallcreeper (Tichodroma muraria). Our method requires that all observed species are recorded. Detectability was <1 and varied over the years. Simulations suggested some robustness, but we advocate recording complete species lists (checklists), rather than recording individual records of single species. The representation of observation effort with its effect on detectability provides a solution to the problem of differences in effort encountered when extracting trend information from haphazard observations. We expect our method is widely applicable for global biodiversity monitoring and modeling of species distributions.  相似文献   
744.
Abstract: Populations of large brown algae of the Laminariales and Fucales (Phaeophyta) have declined or been extirpated from many locations on temperate coasts worldwide. We conducted field surveys and a literature review, and examined herbarium specimens, through which we discovered previously unreported extirpations of large brown algal species from a tropical and subtropical coastline. Sargassum amaliae, S. aquifolium, S. carpophyllum, S. polycystum, and S. spinifex were common habitat‐forming macroalgae that supported diverse assemblages of invertebrates and smaller algae before urbanization began in 1970 along the 45‐km length of Sunshine Coast in Queensland, Australia. Causes of these extirpations are not known, but are consistent with losses of other large brown algal species from coastal areas undergoing urbanization or eutrophication. Sargassum spp. do not have the characteristics thought to protect marine species from extinction (large geographical ranges, occurrence on many different substrata, long‐distance dispersal). Some local Sargassum spp. are endemic to eastern Australia. Abundance of Sargassum is limited by suitable substrata on the sandy southern Queensland coast (370 km). These substrata are 12 rocky headlands separated by long (5–105 km) sandy beaches. Most multicellular propagules (the only motile stage in Sargassum) settle within 1–3 m of parental thalli, which restricts long‐distance dispersal needed to maintain connectivity among populations and to recolonize areas of the headlands from which populations have been extirpated. Local Sargassum spp. could be categorized as data deficient by the International Union for Conservation of Nature (IUCN), but the IUCN vulnerable category is more accurate given extirpations, limited habitat, and the lack of connectivity among populations.  相似文献   
745.
Abstract: There are few empirical data, particularly collected simultaneously from multiple sites, on extinctions resulting from human‐driven land‐use change. Southeast Asia has the highest deforestation rate in the world, but the resulting losses of biological diversity remain poorly documented. Between November 2006 and March 2008, we conducted bird surveys on six landbridge islands in Malaysia and Indonesia. These islands were surveyed previously for birds in the early 1900s, when they were extensively forested. Our bird inventories of the islands were nearly complete, as indicated by sampling saturation curves and nonparametric true richness estimators. From zero (Pulau Malawali and Pulau Mantanani) to 15 (Pulau Bintan) diurnal resident landbird species were apparently extirpated since the early 1900s. Adding comparable but published extinction data from Singapore to our regression analyses, we found there were proportionally fewer forest bird extinctions in areas with greater remaining forest cover. Nevertheless, the statistical evidence to support this relationship was weak, owing to our unavoidably small sample size. Bird species that are restricted to the Indomalayan region, lay few eggs, are heavier, and occupy a narrower habitat breadth, were most vulnerable to extinction on Pulau Bintan. This was the only island where sufficient data existed to analyze the correlates of extinction. Forest preservation and restoration are needed on these islands to conserve the remaining forest avifauna. Our study of landbridge islands indicates that deforestation may increasingly threaten Southeast Asian biodiversity.  相似文献   
746.
Abstract: In the United States, as elsewhere, a growing debate pits national energy policy and homeland security against biological conservation. In rural communities the extraction of fossil fuels is often encouraged because of the employment opportunities it offers, although the concomitant itinerant workforce is often associated with increased wildlife poaching. We explored possible positive and negative factors associated with energy extraction in the Greater Yellowstone Ecosystem (GYE), an area known for its national parks, intact biological diversity, and some of the New World's longest terrestrial migrations. Specifically, we asked whether counties with different economies—recreation (ski), agrarian (ranching or farming), and energy extractive (petroleum)—differed in healthcare (gauged by the abundance of hospital beds) and in the frequency of sexual predators. The absolute and relative frequency of registered sex offenders grew approximately two to three times faster in areas reliant on energy extraction. Healthcare among counties did not differ. The strong conflation of community dishevel, as reflected by in‐migrant sexual predators, and ecological decay in Greater Yellowstone is consistent with patterns seen in similar systems from Ecuador to northern Canada, where social and environmental disarray exist around energy boomtowns. In our case, that groups (albeit with different aims) mobilized campaigns to help maintain the quality of rural livelihoods by protecting open space is a positive sign that conservation can matter, especially in the face of rampant and poorly executed energy extraction projects. Our findings further suggest that the public and industry need stronger regulatory action to instill greater vigilance when and where social factors and land conversion impact biological systems.  相似文献   
747.
Abstract: In light of limited conservation funding, global conservation initiatives are increasingly focused on regions of the planet that have been identified as valuable on the basis of their species diversity, the vulnerability of resident species to extinction, or the perceived pristine nature of their ecosystems. Regions that have been resilient to high rates of extinction have not yet been systematically considered in conservation efforts. We used published range maps for 392 vertebrate species to compare historical and current species ranges. We used the results of the comparison to identify regions of the globe in which no known vertebrate species has been extirpated in the past 200 years. In 17 regions, no detectable vertebrate extinctions occurred in the past 200 years. In 6 other regions, reintroductions of species restored the full historic complement of vertebrate species. The effects of humans on a landscape, as measured by the human‐footprint index, although useful, was not a singularly good predictor of faunal intactness because more than 20% of intact land area was in heavily affected areas (50% of Earth's land area), and several regions where humans have had very little effect did not have intact faunas. Only 22% of intact land area was within protected‐area networks. High‐latitude areas were particularly underrepresented; they made up 3 of the 4 least‐protected areas in our analyses. Our results indicate that although protected areas are in some cases associated with the prevention of extinctions, there are many regions in which human activity coexists with intact vertebrate assemblages. In addition, our new approach for assessing the value of global regions for conservation identifies several regions that are not represented in other prioritization metrics.  相似文献   
748.
Abstract: Conservation development projects combine real‐estate development with conservation of land and other natural resources. Thousands of such projects have been conducted in the United States and other countries through the involvement of private developers, landowners, land trusts, and government agencies. Previous research has demonstrated the potential value of conservation development for conserving species, ecological functions, and other resource values on private lands, especially when traditional sources of conservation funding are not available. Nevertheless, the aggregate extent and effects of conservation development were previously unknown. To address this gap, we estimated the extent and trends of conservation development in the United States and characterized its key attributes to understand its aggregate contribution to land‐conservation and growth‐management objectives. We interviewed representatives from land trusts, planning agencies, and development companies, searched the Internet for conservation development projects and programs, and compiled existing databases of conservation development projects. We collected data on 3884 projects encompassing 1.38 million ha. About 43% of the projects targeted the conservation of specific plant or animal species or ecological communities of conservation concern; 84% targeted the protection of native ecosystems representative of the project area; and 42% provided buffers to existing protected areas. The percentage of protected land in conservation development projects ranged from <40% to >99%, and the effects of these projects on natural resources differed widely. We estimate that conservation development projects have protected roughly 4 million ha of land in the United States and account for about 25% of private‐land conservation activity nationwide.  相似文献   
749.
Abstract: Changes in land use and land cover have affected and will continue to affect biological diversity worldwide. Yet, understanding the spatially extensive effects of land‐cover change has been challenging because data that are consistent over space and time are lacking. We used the U.S. National Land Cover Dataset Land Cover Change Retrofit Product and North American Breeding Bird Survey data to examine land‐cover change and its associations with diversity of birds with principally terrestrial life cycles (landbirds) in the conterminous United States. We used mixed‐effects models and model selection to rank associations by ecoregion. Land cover in 3.22% of the area considered in our analyses changed from 1992 to 2001, and changes in species richness and abundance of birds were strongly associated with land‐cover changes. Changes in species richness and abundance were primarily associated with changes in nondominant types of land cover, yet in many ecoregions different types of land cover were associated with species richness than were associated with abundance. Conversion of natural land cover to anthropogenic land cover was more strongly associated with changes in bird species richness and abundance than persistence of natural land cover in nearly all ecoregions and different covariates were most strongly associated with species richness than with abundance in 11 of 17 ecoregions. Loss of grassland and shrubland affected bird species richness and abundance in forested ecoregions. Loss of wetland was associated with bird abundance in forested ecoregions. Our findings highlight the value of understanding changes in nondominant land cover types and their association with bird diversity in the United States.  相似文献   
750.
Abstract: Antarctic ecosystems are often considered nearly pristine because levels of anthropogenic disturbance are extremely low there. Nevertheless, over recent decades there has been a rapid increase in the number of people, researchers and tourists, visiting Antarctica. We evaluated, over 10 years, the direct impact of foot traffic on the abundance of soil animals and soil properties in Taylor Valley within the McMurdo Dry Valleys region of Antarctica. We compared soils from minimally disturbed areas with soils from nearby paths that received intermediate and high levels of human foot traffic (i.e., up to approximately 80 passes per year). The nematodes Scottnema lindsayae and Eudorylaimus sp. were the most commonly found animal species, whereas rotifers and tardigrades were found only occasionally. On the highly trampled footpaths, abundance of S. lindsayae and Eudorylaimus sp. was up to 52 and 76% lower, respectively, than in untrampled areas. Moreover, reduction in S. lindsayae abundance was more pronounced after 10 years than 2 years and in the surface soil than in the deeper soil, presumably because of the longer period of disturbance and the greater level of physical disturbance experienced by the surface soil. The ratio of living to dead Eudorylaimus sp. also declined with increased trampling intensity, which is indicative of increased mortality or reduced fecundity. At one site there was evidence that high levels of trampling reduced soil CO2 fluxes, which is related to total biological activity in the soil. Our results show that even low levels of human traffic can significantly affect soil biota in this ecosystem and may alter ecosystem processes, such as carbon cycling. Consequently, management and conservation plans for Antarctic soils should consider the high sensitivity of soil fauna to physical disturbance as human presence in this ecosystem increases.  相似文献   
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