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81.
Stanley L. Ponce 《Journal of the American Water Resources Association》1979,15(2):530-535
ABSTRACT: A survey was made to determine the status of formal education in wildland hydrology by colleges and universities in the United States, Canada, and Mexico. As of December 1977 nine institutions offered the B.S. degree, 18 the M.S. degree, and 17 the degree of Ph.D. with a major or minor in watershed management, forest hydrology, or range hydrology. In addition, 8 other schools offer a minor in watershed management. The survey indicated 44 schools in the United States offer a total of 157 courses, five schools in Canada offer 24 courses, and 1 in Mexico offers one course in the related areas. The survey illustrated rapid growth in education programs and it is anticipated that growth will continue. 相似文献
82.
Long range atmospheric transport is the most important sourceof contamination to the natural environment in Norway with manyheavy metals. Investigations based on aerosol studies, bulkdeposition measurements and moss analysis show that airborne transport from other parts of Europe is the major mode for supplyof vanadium, zinc, arsenic, selenium, molybdenum, cadmium, tin,antimony, tellurium, thallium, lead, and bismuth, whereas metalssuch as chromium, nickel, and copper are mainly derived from point sources within Norway and in northwestern Russia close tothe Norwegian border. Elements associated with long range transport show substantial enrichment in the humus horizon of natural soils in southern Norway, sometimes to levels suspected to cause effects on soil microbial processes. E.g. lead concentration values of 150–200 ppm are observed in the mostcontaminated areas in the south as compared to about 5 ppm inthe far north. Elements such as lead and cadmium also show enrichment in some terrestrial food chains. These elements alsoshow considerably elevated levels over background concentrationsin the water and sediment of small lakes in the southern part ofthe country. Retrospective studies based on ombrogenous peatcores indicate that long range transport has been a significantsource of heavy metal contamination in southern Norway for thelast couple of centuries. The deposition of most heavy metals inNorway has been considerably reduced over the last 20 yr, withthe exception of contributions in the north from Russian smelters. 相似文献
83.
The perceptual range of an animal towards different landscape elements affects its movements through heterogeneous landscapes. However, empirical knowledge and modeling tools are lacking to assess the consequences of variation in the perceptual range for movement patterns and connectivity. In this study we tested how changes in the assumed perception of different landscape elements affect the outcomes of a connectivity model. We used an existing individual-based, spatially explicit model for the dispersal of Eurasian lynx (Lynx lynx). We systematically altered the perceptual range in which animals recognize forest fragments, water bodies or cities, as well as the probability that they respond to these landscape elements. Overall, increasing the perceptual range of the animals enhanced connectivity substantially, both qualitatively and quantitatively. An enhanced range of attraction to forests had the strongest impact, doubling immigration success; an enhanced range of attraction to rivers had a slightly lower impact; and an enhanced range of avoidance of cities had the lowest impact. Correcting the enhancement in connectivity by the abundance of each of the landscape elements in question reversed the results, indicating the potential sensitivity of connectivity models to rare landscape elements (in our case barriers such as cities). Qualitatively, the enhanced perception resulted in strong changes in movement patterns and connectivity. Furthermore, model results were highly parameter-specific and patch-specific. These results emphasize the need for further empirical research on the perceptual capabilities of different animals in different landscapes and conditions. They further indicate the usefulness of spatially explicit individual-based simulation models for recognizing consistent patterns that emerge, despite uncertainty regarding animals’ movement behavior. Altogether, this study demonstrates the need to extend the concept of ‘perceptual ranges’ beyond patch detection processes, to encompass the wide range of elements that can direct animal movements during dispersal through heterogeneous landscapes. 相似文献
84.
Managing Aquatic Species of Conservation Concern in the Face of Climate Change and Invasive Species 总被引:2,自引:0,他引:2
Abstract: The difficult task of managing species of conservation concern is likely to become even more challenging due to the interaction of climate change and invasive species. In addition to direct effects on habitat quality, climate change will foster the expansion of invasive species into new areas and magnify the effects of invasive species already present by altering competitive dominance, increasing predation rates, and enhancing the virulence of diseases. In some cases parapatric species may expand into new habitats and have detrimental effects that are similar to those of invading non-native species. The traditional strategy of isolating imperiled species in reserves may not be adequate if habitat conditions change beyond historic ranges or in ways that favor invasive species. The consequences of climate change will require a more active management paradigm that includes implementing habitat improvements that reduce the effects of climate change and creating migration barriers that prevent an influx of invasive species. Other management actions that should be considered include providing dispersal corridors that allow species to track environmental changes, translocating species to newly suitable habitats where migration is not possible, and developing action plans for the early detection and eradication of new invasive species. 相似文献
85.
Abstract: Species range maps based on extents of occurrence (EOO maps) have become the basis for many analyses in broad-scale ecology and conservation. Nevertheless, EOO maps are usually highly interpolated and overestimate small-scale occurrence, which may bias research outcomes. We evaluated geographical range overestimation and its potential ecological causes for 1158 bird species by quantifying EOO map occurrence across 4040 well-studied survey locations in Australia, North America, and southern Africa at the scale of 80–742 km2 . Most species occurred in only 40–70% of the range indicated by their EOO maps. The observed proportional range overestimation affected the range-size frequency distribution, indicating that species are more range-restricted than suggested by EOO maps. The EOO maps most strongly overestimated the distribution of narrow-ranging species and ecological specialists with narrow diet and habitat breadth. These relationships support basic ecological predictions about the relationship between niche breadth and the fine-scale occurrence of species. Consequently, at-risk species were subject to particularly high proportional range overestimation, on average 62% compared with 37% of nonthreatened species. These trends affect broad-scale ecological analyses and species conservation assessments, which will benefit from a careful consideration of potential biases introduced by range overestimation. 相似文献
86.
Abstract: In theory the consideration of life-history characteristics should provide a way of making predictive generalizations about the responses of different species to environmental modification. Nevertheless, few studies have tested the validity of this assumption or attempted to apply it across large numbers of related species. We explored both quantitative and qualitative contrasts between species of waterbirds that have either expanded or contracted their ranges in southern Africa over the past 40 years to test the hypothesis that expansionists and contractionists, respectively, should share life-history characteristics and/or ecological attributes. Similarities and differences in life history and ecology were explored through multivariate statistics. Overall, life-history traits provided an inadequate explanation of whether species would be range expansionists or contractionists. By contrast, ecological attributes of species that related to habitat use correlated well with range changes. In particular, waterbird species that inhabit pans seemed to be preadapted to using human-made dams and impoundments. The ability of many species to use artificial wetlands has aided their westward range expansions into arid regions of southern Africa. By contrast, species that rely on vegetated wetlands and that require reeds for nesting were predisposed to range contraction because their habitats have been severely affected by agricultural development and urbanization. In direct contrast to range expansions, most range contractions were west to east, the eastward contraction reflected the high level of wetland loss and degradation in the eastern lowlands of South Africa. Based on analysis of ecological attributes of regional contractionists, several additional species were identified as of potential conservation concern, although such concern may not as yet have been expressed. 相似文献
87.
Human health risk assessment of explosives and heavy metals at a military gunnery range 总被引:1,自引:0,他引:1
In this research, a risk assessment was undertaken in order to develop the remediation and management strategy of a contaminated
gunnery site, where a nearby flood controlling reservoir is under construction. Six chemicals, including explosives and heavy
metals, posing potential risk to environmental and human health, were targeted in this study. A site-specific conceptual site
model was constructed, based on effective, reasonable exposure pathways, to avoid any overestimation of the risk. Also, conservative
default values were adapted to prevent underestimation of the risk when site-specific values were not available. The risks
posed by the six contaminants were calculated using the API’s Decision Support System for Exposure and Risk Assessment, with
several assumptions. In the crater-formed-area (Ac), the non-carcinogenic risks (i.e., HI values) of tri-nitro-toluene (TNT)
and Cd were slightly larger than 1, but for RDX (Royal Demolition Explosives) was over 50. The total non-carcinogenic risk
of the whole gunnery range was calculated to be 62.5, which was a significantly high value. The carcinogenicity of Cd was
estimated to be about 10−3, while that for Pb was about 5 × 10−4, which greatly exceeded the generally acceptable carcinogenic risk level of 10−4–10−6. It was concluded from the risk assessment that there is an immediate need for remediation of both carcinogens and non-carcinogens
before construction of the reservoir. However, for a more accurate risk assessment, further specific estimations of the changes
in environmental conditions due to the construction of the reservoir will be required; and more over, the effects of the pollutants
to the ecosystem will also need to be evaluated. 相似文献
88.
TARCISO C. C. LEÃO CARLOS R. FONSECA CARLOS A. PERES MARCELO TABARELLI 《Conservation biology》2014,28(5):1349-1359
Understanding how plant life history affects species vulnerability to anthropogenic disturbances and environmental change is a major ecological challenge. We examined how vegetation type, growth form, and geographic range size relate to extinction risk throughout the Brazilian Atlantic Forest domain. We used a database containing species‐level information of 6,929 angiosperms within 112 families and a molecular‐based working phylogeny. We used decision trees, standard regression, and phylogenetic regression to explore the relationships between species attributes and extinction risk. We found a significant phylogenetic signal in extinction risk. Vegetation type, growth form, and geographic range size were related to species extinction risk, but the effect of growth form was not evident after phylogeny was controlled for. Species restricted to either rocky outcrops or scrub vegetation on sandy coastal plains exhibited the highest extinction risk among vegetation types, a finding that supports the hypothesis that species adapted to resource‐limited environments are more vulnerable to extinction. Among growth forms, epiphytes were associated with the highest extinction risk in non‐phylogenetic regression models, followed by trees, whereas shrubs and climbers were associated with lower extinction risk. However, the higher extinction risk of epiphytes was not significant after correcting for phylogenetic relatedness. Our findings provide new indicators of extinction risk and insights into the mechanisms governing plant vulnerability to extinction in a highly diverse flora where human disturbances are both frequent and widespread. Predicción del Riesgo de Extinción de Angiospermas del Bosque Atlántico Brasileño 相似文献
89.
选用青海省三江源地区1964~2013年14个气象台站观测的基本气象数据,利用线性倾向性估计和Mann-Kendall检验方法等分析了三江源地区蒸发皿蒸发量的时空变化和变化趋势,并以完全相关分析方法进行蒸发量上升成因分析。结果表明:三江源地区年蒸发量总体呈显著上升趋势,其线性变化速率为30.1 mm/10 a,夏秋冬季蒸发量均呈显著上升变化,春季变化趋势不明显,夏季和秋季蒸发量上升对年蒸发量上升贡献最大;逐月蒸发量变化趋势均增加,但幅度各异;冬季蒸发量在2011年发生了突变,其余各季和年均未发生突变.蒸发量月际变化规律明显,表现为双峰型分布,双峰出现在5月和7月,最小值出现在1月;季节变化也十分明显,夏季蒸发量最大,其次为春季和秋季,冬季蒸发量最少,表明春夏两季蒸发量的多少对三江源地区水循环起重要作用。年和四季蒸发量呈现出西北部少,东南部及东北部多的分布特点,气候变化速率分布自西向东逐渐增大。蒸发量年际变化不剧烈,年蒸发量变异系数从西北向东南逐渐增大,四季蒸发量变异系数空间分布明显不同。年蒸发量与平均气温总体上呈正相关,与气温日较差、相对湿度呈负相关,平均气温上升、气温日较差和相对湿度下降是三江源地区蒸发量上升的主要因素。 相似文献
90.
The natural range of variation of ecosystems provides reference conditions for sustainable management and biodiversity conservation. We review how the understanding of natural reference conditions of boreal forests in northern Europe has changed from earlier perceptions of even-aged dynamics driven by stand-replacing disturbances towards current understanding highlighting the role of non-stand-replacing disturbances and the resultant complex forest dynamics and structures. We show how earlier views and conceptual models of forest disturbance dynamics, including the influential ASIO model, provide estimates of reference conditions that are outside the natural range of variation. Based on a research synthesis, we present a revised forest reference model incorporating the observed complexity of ecosystem dynamics and the prevalence of old forests. Finally, we outline a management model and demonstrate its use in forest ecosystem management and show how regional conservation area needs can be estimated. We conclude that attaining favourable conservation status in northern Europe’s boreal forests requires increasing emphasis on ecosystem management and conservation for old forest characteristics.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01444-3) contains supplementary material, which is available to authorized users. 相似文献