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1.
本区至今还是综合科学考察的空白区。为查明基本情况,1989年夏以乘汽车路线考察方式穿行该区而作了预查,搜集了当地地质、地理、生物等基本资料。经考察发现,区内野生动物资源丰富,上新世以来火山活动普遍,湖泊众多,矿产资源可能有良好前景;所在区又为自然地域和地质构造的重要界线,对青藏高原研究具有重大科学价值。 相似文献
2.
3.
当前,由于缺乏对气象服务投入量与产出量准确而完整的统计,要对气象服务的各种经济效益作出总体评价是困难的。然而,在专项气象服务中,却不乏原始、完整而准确的资料。作者从此出发,讨论了专项气象服务经济效益评价的理论。并通过实地调查,以彭州市气象局几项专项气象服务为例探讨了评价技术。 相似文献
4.
卢秀容 《广东海洋大学学报》2001,21(4):47-51
在市场经济的条件下,渔业企业作为一个独立的投资主体,对任何一项投资,它都会考虑其经济效益.本文通过一个实例,阐述了渔业企业在投资之前,如何从财务上评估该项投资的经济效益. 相似文献
5.
农业自然资源据其在农业利用过程中的地位可分为两类:一类是生成农业自然资源的环境,另一类为可资直接利用的自然生成物(即狭义的农业自然资源)。陕西秦巴山区自然环境的主要特点是:复合山体高峻庞大,地跨暖温带和北亚热带,垂直分异明显。区内有:森林、草场、野生生物、林特产与农作物等多种农业自然资源。据此,提出了本区农业自然资源的开发利用途径。 相似文献
6.
运输系统的区域效应研究 总被引:1,自引:0,他引:1
运输系统改进—运距缩短—产业布局调整这一空间过程对不同的区域可能具有完全不同的意义。本文通过对一个两区域—两部门经济模型的研究得出结论:当较落后的资源产区与经济中心之间的距离由于运输系统的改进而缩短时,资源产区的经济结构向单一化转变,初级产品的生产和输出在经济建设中逐渐占主导地位,加工工业逐渐萎缩,地方经济发展受到阻碍,而且这种变化是在距离的某一特定值处突然出现的,带有跃变的性质。这一研究结果表明,对区域运输系统的任何改进措施都应该慎而行之,以免造成与本来目标相悖的区域效应。 相似文献
7.
Thembela Kepe 《Geoforum》2008,39(2):958-968
Different types of vegetation found in local environments are of value to rural livelihoods of many African households. However, the dominant way of expressing this value, which is mainly through economic valuation studies, is potentially limiting this knowledge’s usefulness in policy and research, due to the inability to present full picture. Using literature review and insights from field work, the paper argues that realized and notional values of vegetation to rural livelihoods are socially constructed and contested, and - in addition to understanding local livelihood context, which include social difference, and ecological dynamics - a focus on social institutions as terrains of negotiation is crucial. This means that resource value in rural livelihoods can be realized through contested and negotiated access arrangements that are mediated by complex institutions at local and external levels. 相似文献
8.
Gregory P. Marchildon Suren Kulshreshtha Elaine Wheaton Dave Sauchyn 《Natural Hazards》2008,45(3):391-411
Agriculture in the southern Great Plains of Canada has been particularly vulnerable to prolonged episodes of drought. Using
climate data and a precipitation minus potential evapotranspiration index, the extent of the region’s exposure to drought
is examined. Between 1914 and 1917, the Dry Belt was particularly vulnerable to drought, whereas after 1928, a much larger
region known as the Palliser Triangle covering most of southern Alberta and Saskatchewan was much more exposed to drought.
These droughts provoked major institutional adaptation, in particular the establishment of the Special Areas Board by the
Government of Alberta, and the creation of the Prairie Farm Rehabilitation Administration by the Government of Canada. Both
organizations have proved to be relatively permanent public adaptations to the natural hazard of drought in the region. Moreover,
these earlier experiences with prolonged drought as well as institution-building may be of value in helping the residents
of the Palliser Triangle adapt to predicted climate changes in the future as well as anticipate some of the barriers to effective
institutional adaptation. 相似文献
9.
In this study we test Talley's hypothesis that Oyashio winter mixed-layer water (26.5–26.6σ θ) increases its density to produce the North Pacific Intermediate Water (NPIW) salinity minimum (26.7– 26.8σθ) in the Mixed Water Region, assuming a combination of cabbeling and double diffusion. The possible density change of Oyashio
winter mixed-layer water is discussed using an instantaneous ratio of the change of temperature and salinity along any particular
intrusion (R
l
). We estimate the range of R
l
DD
required to convert Oyashio winter mixed-layer water to the NPIW salinity minimum due to double diffusion, and then assume
double-diffusive intrusions as this conversion mechanism. A double-diffusive intrusion model is used to estimate R
l
DD
in a situation where salt fingering dominates vertical mixing, as well as to determine whether Oyashio winter mixed-layer
water can become the NPIW salinity minimum. Possible density changes are estimated from the model R
l
DD
by assuming the amount of density change due to cabbeling. From these results, we conclude that Oyashio winter mixed-layer
water contributes to a freshening of the lighter layer of the NPIW salinity minimum (around 26.70σθ) in the MWR. 相似文献
10.
Carmen E. Morales Humberto E. González Gabriel Yuras Leonardo R. Castro 《Progress in Oceanography》2007,75(3):452-469
The oceanographic setting and the planktonic distribution in the coastal transition zone off Concepción (∼35-38°S, ∼73-77°W), an area characterized by its high biological production, were assessed during two different seasons: austral spring with equatorward upwelling favorable winds and austral winter with predominately northerly winds. Oceanographic and biological data (total chlorophyll-a, particulate organic carbon, microplankton, large mesozooplankton >500 μm as potential consumers of microplankton) were obtained during two cruises (October 1998, July 1999) together with satellite imagery for wind stress, geostrophic flow, surface temperature, and chlorophyll-a data. The physical environment during the spring sampling was typical of the upwelling period in this region, with a well-defined density front in the shelf-break area and high concentrations of surface chlorophyll-a (>5 mg m−3) on the shelf over the Itata terrace. During the winter sampling, highly variable though weakly upwelling-favorable winds were observed along with lower surface chlorophyll-a values (<2 mg m−3) on the shelf. In the oceanic area (>100 km from the coast), cyclonic and anti-cyclonic eddies were evident in the flow field during both periods, the former coinciding with higher chlorophyll-a contents (∼1 mg m−3) than in the surrounding waters. Also, a cold, chlorophyll-a rich filament was well defined during the spring sampling, extending from the shelf out to 350-400 km offshore. Along a cross-shelf transect, the micro- and meso-planktonic assemblages displayed higher coastal abundances during the spring cruise but secondary peaks appeared in the oceanic area during the winter cruise, coinciding with the distribution of the eddies. These results suggest that the mesoscale features in this region, in combination with upwelling, play a role in potentially increasing the biological productivity of the coastal transition zone off Concepción. 相似文献