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161.
天目山是浙江省珍稀濒危植物最丰富的地区,共有国家保护的珍稀濒危植物25科、34属、37种,其中属二级保护13种,三级保护24种.论述了天目山珍稀濒危植物的区系特点、类型及地理分布,列举了它们的一些利用价值,最后提出了保护天目山珍稀濒危植物的一系列建议. 相似文献
162.
浙江山区的珍稀濒危植物较为丰富,有67科、108属、125种.论述了当地珍稀濒危植物的特点、地理分布、属和种的地理成分,探讨了珍稀濒危植物的就地保护、迁地保护和离体保存. 相似文献
163.
In this paper the researches made in 1981-1990 have identified that the annual soil loss in the Three Gorges region is 157 million t. and the annual incoming sediment load of the Three Gorges reservoir is 40 million t. Soil erosion increases with the destruction of vegetative cover and its subsequent evolution. The annual amounts of sediment erosion for forest land, shrub land, grassland and farmland make up respectively 6.19%, 10.76%, 23.05% and 60% of the total erosion of the Three Gorges region; the quantities of incoming sediment load to the Yangtze River from the above four types of land account for 5.95%, 12.42%, 35.46% and 46.1 % of the total amount of sediment transported to the reservoir. The farmland of offers the main source of sediment. Gravitational erosion produces more bed loads, which will present serious threat to the Three Gorges Project if entering the reservoir. Resettlement of people to the upper parts of the mountainous areas for agricultural production will increase the sediment yield of the Three Gorges region by 10-20 million t and increase the incoming sediment of the Yangtze River by 50-60 million t. Consequently, it is necessary to make a realistic assessment of the soil erosion in the Three Gorges region. 相似文献
164.
凉山州境内的富铁矿按成因可分为火山型、热液型、沉积变质型、沉积型等类型,本文逐一对其分布、地质特征及规模等方面进行了叙述和总结;对主要富铁矿产地和储量作了统计,并介绍了主要矿区开发现状及经济效益。提出了今后矿山开发、资源保扩及寻找富铁矿的建议。 相似文献
165.
青藏高原沼泽合理利用与生态环境保育 总被引:4,自引:0,他引:4
青藏高原有沼泽约491.3万hm2,是世界上最高的湿地。通过概要介绍高原沼泽湿地基本类型及其分布,重点阐述沼泽湿地利用、环境变化现状与存在的问题,为了保护高原生态环境,并持续利用湿地资源,提出了初步的看法和建议。 相似文献
166.
Hoffmann TC 《Marine pollution bulletin》2002,44(11):1281-1293
This research focuses on coral reef health in the South Pacific region, an area of high global coral diversity. Coral reef health surrounding four island case studies in the Cook Islands and Fiji have been assessed in areas that have not been previously surveyed. This study compares four islands with barrier and fringing reefs that have different levels of economic development, population pressure, land-use practices, and marine management practices. This interdisciplinary research methodology includes both ecological and social data collection to further understanding of human environment interactions. In comparing the reefs with different socio-economic factors, this research shows that reefs with traditional systems of resources management are healthier, population pressure is not the main factor causing the demise of the reefs and agro-industry is the main industry causing the degradation of the reef in these four South Pacific Islands. In addition, researchers need to use a whole reef perspective to examine coral reef health. 相似文献
167.
168.
The use of riparian vegetated filter strips to reduce river sediment loads: an overestimated control measure? 总被引:1,自引:0,他引:1
The spatially distributed soil erosion and sediment delivery model WATEM/SEDEM was used to simulate the impact of riparian vegetated filter strips (RVFSs) on river sediment delivery at different spatial scales. For a field plot with a straight slope, sediment reduction by the RVFSs is comparable to results obtained through experimental set‐ups elsewhere (i.e. >70%). However, at the scale of an entire catchment, sediment reduction is much less (i.e. ±20%) due to (1) overland flow convergence, which reduces the sediment trapping efficiency of an RVFS, and (2) because part of the sediment bypasses the RVFSs through ditches, sewers and road surfaces. These results suggest that, at the catchment scale, RVFSs should be accompanied with other conservation techniques that are more appropriate for reducing river sediment loads, and that also reduce on‐site soil erosion. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
169.
170.
1 Introduction The mean meridional circulation plays an important role in the transportation and balance of heat, momen- tum, vortex and vapor between different latitudes. According to the data analysis, there are three circula- tions from the equator to the polar area: the Hadley circulation, a heat-driven circulation which rises around the equator and sinks at a certain latitude; the subpolar circulation, another heat-driven circulation around the polar area; and the Ferrel circulation, an i… 相似文献