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941.
GIS在林业专题制图中的应用 总被引:10,自引:0,他引:10
论述了运用于理信息系统软件完成应用遥感技术进行思茅地区样地清查及进行“二项调查”的制衅工作,重点阐明了整个制作过程、成果分析、该注意的几点事项。成果得到相关部门的认可,该方法可应用于林业专题图的制作。 相似文献
942.
The subject of risk management is attracting more and more attention around the world. The risk of forest fire disasters should
be faced and dealt with for forest fires cannot be avoided. Treating forest fire disasters as a risk management issue promotes
important measures and methods for fire fighters to prevent, reduce and control the risks of forest fires. In this paper,
the risk concept and risk connotation as well as the management risks for forest fire suppression are discussed clearly. Issues
such as risk judgments, risk analysis, risk control and the assessment of risk, including their contents and corresponding
methods are clarified.
Translated from Forest Resources Management, 2006, 2: 24–27 [译自: 林业资源맜理] 相似文献
943.
After an absence of approximately 70 years, gray wolves (Canis lupus) were re-introduced into Yellowstone National Park in the mid-1990s. We studied the potential influence of wolf/ungulate interactions upon willow (Salix spp.) growth in the valleys of the Gallatin and Lamar Rivers, as well as Slough and Soda Butte Creeks, in the northern Yellowstone ecosystem. When we compared willow heights from photographs taken prior to 1998 (willows <2 m tall) with those taken in 2004, we found an increase in willow height for 22 of 42 sites within the study area. Based on comparisons of the chronosequence photos, since wolf introduction none of the 16 upland riparian sites showed an increase in willow height, while 22 of 26 of the valley-bottom riparian sites had willow height increases. In 2004, willow height exhibited a strong inverse relationship with the percentage of browsed stems (r = −0.81, p < 0.01, n = 42). Results of regressions for valley-bottom sites indicated that view distance, impediment distance, and the number of bison (Bison bison) flops were inversely related to willow height (p ≤ 0.02). Increased willow heights were not significantly (p = 0.18) related to patterns of moisture availability. Willow height increases documented in this study appear to have been at least partially due to behaviorally mediated trophic cascades involving wolves and ungulates, via a mechanism of predation risk. While willow release (i.e., increased height growth) within the study area is in a very early stage, results suggest potentially important indirect effects of a top carnivore in a terrestrial food chain that may aid in the restoration of riparian species and the preservation of biodiversity. 相似文献
944.
We summarized the status of wolves (Canis lupus), elk (Cervis elaphus), and woody browse conditions during the 20th century for the upper Gallatin elk winter range in southwestern Montana, USA. During this period, wolves were present until about the mid-1920s, absent for seven decades, and then returned to the basin in 1996. A chronosequence of photographs, historical reports, and studies indicated willows (Salix spp.) along streams became heavily browsed and eventually suppressed following the removal of wolves, apparently due to unimpeded browsing by elk. However, after wolf establishment in 1996, browsing intensity on willows lessened in some areas and we hypothesized that, at both a landscape and fine scale, browsing pressure reflects terrain configurations influencing predation risk (nonlethal effects), in conjunction with lower elk densities (lethal effects). We measured browsing intensity and heights of Booth willow (S. boothii) along 3000 m reaches of the Gallatin River and a tributary to examine the potential influence of wolf/elk interactions upon willow growth. Where the Gallatin Valley is relatively narrow (high predation risk), willows began releasing in 1999 and by 2002 were relatively tall (150–250 cm). In contrast, willow heights along a wider portion of the Gallatin Valley, along the open landscape of the tributary, and an upland site (all low predation risk) generally remained low (<80 cm). We identified terrain and other features that may contribute to the perceived risk of wolf predation, by elk for a given site. Although alternative mechanisms are discussed, changes in willow communities over time following wolf removal and their subsequent reintroduction were consistent with a top-down trophic cascade model involving nonlethal and possibly lethal effects. If similar top-down effects upon vegetation hold true in other regions of North America and other parts of the world where wolves have been extirpated, wolf recovery may represent a management option for helping to restore riparian plant communities and conserve biodiversity. 相似文献
945.
蒙特卡罗在项目融资风险评估中的应用 总被引:1,自引:0,他引:1
项目融资具有强大的筹资能力,在我国的应用具有广阔的前景。但项目融资也存在巨大的风险,需要对风险加以管理.风险评估是风险管理的重要步骤。本文通过介绍蒙特卡罗的基木概念、基本原理和工作程序,采用蒙特卡罗模拟与Matlab程序相结合的方法进行了项目融资风险定量评估,并结合实例对此方法予以说明。 相似文献
946.
浅论生态补偿制度建立及原理 总被引:25,自引:0,他引:25
生态补偿是为防止生态资源配置扭曲,通过制度设计来修正发展平衡的问题。本文简要介绍了生态补偿的由来,分析了生态补偿的公共产品、外部效应和生态资本三大理论基础,回顾了中国生态补偿工作开展的情况,对建立生态补偿机制进出了一些建议。 相似文献
947.
贵州省退耕还林工程生态效益监测与评价初探 总被引:4,自引:0,他引:4
通过对贵州省退耕还林10个生态效益监测网络县设置的100个坡面固定样地,以及5个典型县16个坡面径流场各生态指标2年观测数据的分析,得出退耕还林后监测区各生态指标的改善情况如下:退耕还林后2年内土壤侵蚀模数和流失量减少78%,监测区植被覆盖率由12.4%增加到38.7%,平均综合生态效益指数已由0.18上升到0.53。 相似文献
948.
第二代杉木林养分动态研究 总被引:3,自引:0,他引:3
根据连续定位观测所取得的数据,对4个小集水区第二代10年生杉木人工林生态系统中的养分循环进行了研究.结果表明.集水区由降水输入的N、P、K、Ca、Mg等营养元素总计为59.285kg/hm2a,径流输出为38.938kg/hm2a,净积累量为20.347kg/hm2a.与该林分7年生时相比,净积累量提高了7.2%,说明集水区第二代杉木林生态恢复处于进展的变化过程. 相似文献
949.
廖显春 《中南林业科技大学学报(自然科学版)》2001,21(2):96-99
概述了目前我国森林环境价值评价的理论基础和评价方法,并对其难点进行了分析,阐述了构建我国特色的评价理论框架及评价体系的必要性,指出只有建立森林生态环境定位观测站及其动态监测体系,才能科学计量、评估森林生态环境价值. 相似文献
950.