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991.
Despite increasing attention to management of headwater streams as sources of water, sediment, and wood to downstream rivers,
the extent of headwater channels and perennial flow remain poorly known and inaccurately depicted on topographic maps and
in digital hydrographic data. This study reports field mapping of channel head and perennial flow initiation locations in
forested landscapes underlain by sandstone and basalt lithologies in Washington State, USA. Contributing source areas were
delineated for each feature using a digital elevation model (DEM) as well as a Global Positioning System device in the field.
Systematic source area–slope relationships described in other landscapes were not evident for channel heads in either lithology.
In addition, substantial variability in DEM-derived source area sizes relative to field-delineated source areas indicates
that in this area, identification of an area–slope relationship, should one even exist, would be difficult. However, channel
heads and stream heads, here defined as the start of perennial flow, appear to be co-located within both of the lithologies,
which together with lateral expansion and contraction of surface water around channel heads on a seasonal cycle in the basalt
lithology, suggest a controlling influence of bedrock springs for that location. While management strategies for determining
locations of channel heads and perennial flow initiation in comparable areas could assign standard source area sizes based
on limited field data collection within that landscape, field-mapped source areas that support perennial flow are much smaller
than recognized by current Washington State regulations. 相似文献
992.
To investigate how the perceptions and behaviour of visitors to coral reefs are influenced by their prior experience and knowledge
of marine life, a questionnaire-based study was undertaken at sites in the Ras Mohammed National Park and at Sharm El Sheikh,
South Sinai, Egypt. It was evident that over the 10–20 years during which these reefs have deteriorated (mainly due to reef-flat
trampling), there have been interrelated shifts in the nature of visitors making use of them. First, there has been a shift
from experienced divers and snorkellers to inexperienced snorkellers and non-snorkellers with a poorer knowledge of reef biology.
Second, there has been a shift in the predominant nationalities of visitors, from German and British, through Italian, to
Russian. More recent user groups both stated and showed that they had less experience of snorkelling; they also showed less
knowledge of marine life and less interest in learning about it. Visitor perceptions of both the state of the marine life
on the reefs and the acceptability of current visitor numbers also varied between groups. More recent visitor groups and visitors
with less knowledge were more satisfied with reef health. In general, however, visitor perceptions of reef health did not
correlate well with actual reef conditions, probably because more experienced visitors preferred less impacted sites with
which they were nevertheless less satisfied than inexperienced visitors at heavily impacted sites. More recent visitor groups
were also less bothered by crowding on the shore or in the water. Consequently, the apparent “social carrying capacity” of
sites seems to be increasing to a level well above the likely “ecological carrying capacity”. 相似文献
993.
994.
Cities are developing innovative strategies to combat climate change but there remains little knowledge of the winners and losers from climate-adaptive land use planning and design. We examine the distribution of health benefits associated with land use policies designed to increase vegetation and surface reflectivity in three US metropolitan areas: Atlanta, GA, Philadelphia, PA, and Phoenix, AZ. Projections of population and land cover at the census tract scale were combined with climate models for the year 2050 at 4 km × 4 km resolution to produce future summer temperatures which were input into a comparative risk assessment framework for the temperature-mortality relationship. The findings suggest disparities in the effectiveness of urban heat management strategies by age, income, and race. We conclude that, to be most protective of human health, urban heat management must prioritize areas of greatest population vulnerability. 相似文献
995.
Ecosystems are essential in providing multiple services to society. However, understanding ecosystem services (ESS) in terms of spatial distribution and trade-offs still remains a challenge for landscape planners and natural resource managers. In this paper, we analyzed the supply of a set of ESS – carbon storage, soil erosion protection, biodiversity, and recreation – within the landscape surrounding the city of Bari in Southern Italy. Through an analysis of this landscape, which includes natural protected areas, such as Natura 2000 Network sites, national and regional parks and nature reserves, and in view of the recent Fitness Check of the Nature Directives, we aimed to provide answers to the following questions: (i) Where are the areas of high and low supply of individual ecosystem services located?; (ii) Where do ecosystem service trade-offs (i.e., ‘hotspots’ and ‘coldspots’) occur?; and (iii) To what extent are ecosystem service hotspots and coldspots located within or outside of natural protected areas? Results show that most of the landscape in the study area supplied at least one of the selected ESS and that ESS hotspots were mostly located within forested and/or natural areas. Hotspots occupied 8.0% of the total landscape, with 23.7% located in natural protected areas. Coldspots were scarce and equal to 2.4%; they constituted only 0.1% of natural protected areas. Almost all of the landscape (89.6%) consists of intermediate areas (i.e., between hotspots and coldspots); 76.2% of natural protected areas consists of intermediate areas. This latter finding is relevant because the high intermediate classes are potentially high-performing areas, which lie mainly on the borders of protected spaces; they can positively influence ecological processes and thus enhance a wide-ranging provision of ESS. Our results highlight the importance of analyzing landscapes to facilitate the selection of priority areas where management efforts would yield maximum benefits. 相似文献
996.
Leila T. Hatch Christopher W. Clark Sofie M. Van Parijs Adam S. Frankel Dimitri W. Ponirakis 《Conservation biology》2012,26(6):983-994
The effects of chronic exposure to increasing levels of human‐induced underwater noise on marine animal populations reliant on sound for communication are poorly understood. We sought to further develop methods of quantifying the effects of communication masking associated with human‐induced sound on contact‐calling North Atlantic right whales (Eubalaena glacialis) in an ecologically relevant area (~10,000 km2) and time period (peak feeding time). We used an array of temporary, bottom‐mounted, autonomous acoustic recorders in the Stellwagen Bank National Marine Sanctuary to monitor ambient noise levels, measure levels of sound associated with vessels, and detect and locate calling whales. We related wind speed, as recorded by regional oceanographic buoys, to ambient noise levels. We used vessel‐tracking data from the Automatic Identification System to quantify acoustic signatures of large commercial vessels. On the basis of these integrated sound fields, median signal excess (the difference between the signal‐to‐noise ratio and the assumed recognition differential) for contact‐calling right whales was negative (?1 dB) under current ambient noise levels and was further reduced (?2 dB) by the addition of noise from ships. Compared with potential communication space available under historically lower noise conditions, calling right whales may have lost, on average, 63–67% of their communication space. One or more of the 89 calling whales in the study area was exposed to noise levels ≥120 dB re 1 μPa by ships for 20% of the month, and a maximum of 11 whales were exposed to noise at or above this level during a single 10‐min period. These results highlight the limitations of exposure‐threshold (i.e., dose‐response) metrics for assessing chronic anthropogenic noise effects on communication opportunities. Our methods can be used to integrate chronic and wide‐ranging noise effects in emerging ocean‐planning forums that seek to improve management of cumulative effects of noise on marine species and their habitats. Cuantificación de la Pérdida de Espacio de Comunicación Acústica para Ballenas Francas Dentro y Alrededor de un Santuario Marino Nacional en E. U. A. 相似文献
997.
三峡地区农业经济监测原理与方法研究 总被引:2,自引:0,他引:2
提出了经济系统抟动监测原理,认为受扰动X作用的系统S的特征指标(监测指标)O的变化量△O分为由系统S自身发展引起的变化量△O和由扰动X的作用引起的变化量△Ox,即△O=△O+△Ox,监测的目的是考察由扰动X引起的指标O的变化量△Ox,提出了建立经济系统监测指标体系。针对5项原则和三峡地区农业经济指标体系。针对不同系统特点和扰动特性,提出8种监测方法。以对三峡库区秭归县水田坝乡眩坝区域柑桔产业开发对 相似文献
998.
对哈密市区锅炉烟尘验收监测结果作了分析阐述,论述了市区烟尘控制区烟尘排放规律及特点,并对监测统计结果进行了小结,为日后的实测工作积累经验。 相似文献
999.
三峡库区扩种龙眼荔枝的适宜性分析 总被引:1,自引:0,他引:1
荔枝与龙眼系亚热带水果,集中分布于闽粤两省,三峡库区上段河谷两侧也有零星分布,是该类水果分布的最北界。这类水果在训区栽培始于汉唐时代,并被列为贡品荔枝与龙眼系喜温性水果,库区栽培间冻害发生,成为限制扩大栽培的主要因素,故多分布于万县-重庆江段两海拔200m上下地段,水库蓄水后,原栽培区部分被淹没,但水体有增温作用,为扩大栽培提供了有利的条件。研究了万县-重庆沿江两岸河谷地段与非河谷地段适宜载种范围 相似文献
1000.
广西喀斯特岩溶石山面积占全区总面积的33.3%,森林植被的严重破坏是这些地区贫困落后的主要原因。对广西喀斯特地区的综合治理开发,要重视对森林植被及珍稀濒危植物的保护。该区至少有290种石山植物为珍稀濒危植物,它们中许多有重要经济用途,在保护的基础上,引种发展一些种类是山区脱贫致富的一条途径。 相似文献