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521.
从安全角度提出了关于各类地区、各等级的汽车运材公路的主要技术指标,阐述了道路环境与行车安全的关系,提出了运材道路的防雪、防滑和冰湖防治的具体措施。  相似文献   
522.
Measurements of aerosol size-separated number concentrations were performed in March 2001 on the Tama Hills of Japan, located near regions of heavy industry. The concentrations of particles larger than 1.0 μ m in diameter dramatically increased during the Kosa phenomena on 6–8 and 18–24 March. The number concentrations of coarse particles (> 3.0 μm) showed distinct diurnal variations, especially during the Kosa events. Fine particles smaller than 0.5 μm increased when the relative humidity was high and the wind speed was low. On the other hand, the coarse particles concentrations were well correlated with wind speed and temperature. The dry deposition velocity of the coarse particles at the forest canopy was estimated from the nighttime decrease in the number concentrations.  相似文献   
523.
Riparian areas of large streams provide important habitat to many species and control many instream processes — but is the same true for the margins of small streams? This review considers riparian areas alongside small streams in forested, mountainous areas of the Pacific Northwest and asks if there are fundamental ecological differences from larger streams and from other regions and if there are consequences for management from any differences. In the moist forests along many small streams of the Pacific Northwest, the contrast between the streamside and upslope forest is not as strong as that found in drier regions. Small streams typically lack floodplains, and the riparian area is often constrained by the hillslope. Nevertheless, riparian‐associated organisms, some unique to headwater areas, are found along small streams. Disturbance of hillslopes and stream channels and microclimatic effects of streams on the riparian area provide great heterogeneity in processes and diversity of habitats. The tight coupling of the terrestrial riparian area with the aquatic system results from the closed canopy and high edge‐to‐area ratio for small streams. Riparian areas of the temperate, conifer dominated forests of the Pacific Northwest provide a unique environment. Forest management guidelines for small streams vary widely, and there has been little evaluation of the local or downstream consequences of forest practices along small streams.  相似文献   
524.
In recent years, researchers and policy makers have recognized that nontimber forest products (NTFPs) extracted from forests by rural people can make a significant contribution to their well-being and to the local economy. This study presents and discusses data that describe the contribution of NTFPs to cash income in the dry deciduous forests of Orissa and Jharkhand, India. In its focus on cash income, this study sheds light on how the sale of NTFPs and products that use NTFPs as inputs contribute to the rural economy. From analysis of a unique data set that was collected over the course of a year, the study finds that the contribution of NTFPs to cash income varies across ecological settings, seasons, income level, and caste. Such variation should inform where and when to apply NTFP forest access and management policies.  相似文献   
525.
人口密度对森林火灾发生频率的影响   总被引:6,自引:0,他引:6  
人类活动是引发森林火灾的主要原因之一,在中国、日本等国家,90%以上的森林火灾是由人为因素引起的。为了量化人类活动对森林火灾的影响,本文基于日本的三级网格系统,对日本全国范围内近年来的森林火灾数据、土地利用率数据和人口密度数据进行了综合分析,研究了人口密度对火灾发生频率的定量影响规律。结果表明:森林火灾发生频率与人口密度之间呈现出幂律关系,经过一步的分析,发现两者之间存在具有边界效应的简单关系,即渐近幂律分布。本文的研究结果对于森林火灾的防治,特别是对于火险的预测具有实用意义。  相似文献   
526.
发挥地方资源优势,促进油茶产业化   总被引:2,自引:0,他引:2  
本文对实行油茶产业化的必要性和可能性进行了详细论述,并为发展南方丘陵地方特色经济林-油茶林资源,促进其产业化提供了有利的对策。  相似文献   
527.
ABSTRACT: Forest buffers adjacent to water bodies are widely prescribed in forest management to protect ecological functions of riparian systems. To date, buffers have been applied on the landscape uniformly without quantifying their effectiveness or the effects they have on landscape characteristics. Our objective was to quantify landscape characteristics (amount of edge and interior forest) when buffers were applied to water bodies in a 100 by 100 km area of northern Minnesota. We used a Landsat classified image in a geographic information system platform to apply two buffer widths ?28.5 m and 57 m — to water bodies, including nonforested wetlands, intermittent or perennial streams, and lakes. A total of 107,141 ha (18.3 percent) of the forest area was adjacent to and within 28.5 m of these water bodies, while 201,457 ha of forest was within 57 m, representing 34.4 percent of the total forest area. Imposing a 28.5 m buffer on water bodies increased the amount of edge and interior forest in the study area. When water bodies were buffered with a 57 m forest strip, we found a slight increase in forest edge from the current condition, and this buffer width resulted in the largest amount of interior forest. Interior forest increased with the 57 m buffer due to the density of water bodies in this region; adjacent water bodies coalesced when buffers were applied and formed isolated forest islands that contained forest interior habitat. Instead of wholesale application of set width riparian buffers, we suggest that ecological conditions of riparian areas be evaluated on a site level and that areas that currently provide important riparian conditions be maintained on the landscape with appropriate management practices.  相似文献   
528.
Cultural taboos and their sanctionshave helped to check abuse of the environmentat least among the local people. The disregardfor these traditional checks and balancesespecially among Christians has adverselyaffected their enforcement at this time. Theenvironment and culture preservation inAwka-South were investigated. The faithfulobservance of the traditional laws in the studyarea was attributed to the fact that Awka-Southarea had remained occupied by the same peoplefor centuries. The study showed that thepreserved forests and their shrines in Nibotown have largely remained intact. In Nisetown, however, with nine shrines still inexistence, the rules have relaxed a little,mainly because they embraced modernization. Inthis town, the fringes of the forests may beused for farming but no felling of trees wouldbe allowed. The ``god' of the shrine in Obunaguvillage was much revered until the advent ofChristianity. This religion has had an erodingeffect on the taboos, which were put in placeto protect their forests and streams. Theabandonment of traditional cultural practicesis doing harm that goes beyond the abrogationof traditional cultural practices to seriousthreat to natural environmental structures. Thecultures of the different tribes in Nigerianeed to be revisited for evaluation and studiesto enable their integration into modernpractices that will make the environment moresustainable. This will be more productive thanthe unilateral introduction of programs,execution, and maintenance methods that arecompletely new, or in many cases run contraryto the cultural practices of the local peopleand tribes of Nigeria.  相似文献   
529.
Conservation of Biodiversity: How Are We Doing?   总被引:1,自引:0,他引:1  
A question rarely raised in discussions on biodiversity conservation, but surely the biggest question of all, is “How much time do we have left before the mass extinction underway surpasses our best efforts to contain it?” This prompts a further prime question because—and unlike all other problems, whether environmental or otherwise—the biotic crisis threatens to leave a severely impoverished planet for millions of years ahead; “Why do we not undertake the necessary actions to get on top of the problem before it gets on top of us?”  相似文献   
530.
作者以生态旅游理论为基础,分析了我国森林生态旅游的发展状况,并以加入WTO为背景从中找出存在的问题,进而提出入世后推进我国森林生态旅游发展的对策。  相似文献   
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