首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
当前,我国林业的外部环境和内部条件已经发生了深刻的变化。加入WTO要求减少政府对经济活动的干预;社会对林业主导需求的变化使林业自身社会公益事业的性质更为突出;非公有制林业广泛兴起,全社会办林业方兴未艾。  相似文献   

3.
王春玲  朱宏伟 《森林工程》2003,19(4):31-31,47
根据国际FIDIC条款对工程变更程序及管理的规定,系统地阐述公路施工中关于工程变更的概念、分类、步骤及程序,使之在应用中更科学、更规范、更标准、更有效。  相似文献   

4.
Forest change is of great concern for land use decision makers and conservation communities. Quantitative and spatial forest change information is critical for addressing many pressing issues, including global climate change, carbon budgets, and sustainability. In this study, our analysis focuses on the differences in geospatial patterns and their changes between federal forests and nonfederal forests in Alabama over the time period 1987–2005, by interpreting 163 Landsat Thematic Mapper (TM) scenes using a vegetation change tracker (VCT) model. Our analysis revealed that for the most part of 1990 s and between 2000 and 2005, Alabama lost about 2% of its forest on an annual basis due to disturbances, but much of the losses were balanced by forest regeneration from previous disturbances. The disturbance maps revealed that federal forests were reasonably well protected, with the fragmentation remaining relatively stable over time. In contrast, nonfederal forests, which are predominant in area share (about 95%), were heavily disturbed, clearly demonstrating decreasing levels of fragmentation during the time period 1987–1993 giving way to a subsequent accelerating fragmentation during the time period 1994–2005. Additionally, the identification of the statistical relationships between forest fragmentation status and forest loss rate and forest net change rate in relation to land ownership implied the distinct differences in forest cutting rate and cutting patterns between federal forests and nonfederal forests. The forest spatial change information derived from the model has provided valuable insights regarding regional forest management practices and disturbance regimes, which are closely associated with regional economics and environmental concerns.  相似文献   

5.
2008年1月至2009年12月,在黄河三角洲地区以每月一次的调查频度对水鸟开展连续两年的调查,共记录到水鸟107种,累计403992只次,其中2008年调查水鸟102种,数量256385只次,2009年调查水鸟106种,数量147607只次。受威水鸟2008年度11种,17604只次,2009年度12种,10695只次。水鸟种群数量在3~5月和10~12月为高峰值,呈双曲线变化,种类4月和10月最多。2009年1~2月极度严寒的天气影响了水鸟的数量,导致数量锐减,并持续影响到2009年。最后,论文还分别对雁鸭类、秧鸡类、鸻鹬类、鸥类、鹭类、鹤类、鹳类等重点水禽种群变化进行了分析。  相似文献   

6.
江苏省森林资源二类调查消长动态变化分析   总被引:4,自引:0,他引:4  
江苏省最近的森林资源二类调查分别为1989年和2009年完成,两期调查都获取了详实的森林资源数据。通过全面对比调查结果,从林地面积、林种结构、林木蓄积、龄组结构、树种组成和森林资源质量等6个方面客观反映了全省森林资源动态变化现状,并深入分析了森林资源面积、蓄积和林种等主要因子的变化原因,总结了全省森林资源的变化特点:①...  相似文献   

7.
伊春林区的林业已从传统林业向生态林业方向转变。资源型城市经济转型,发展非林替代产业,特别是林区广大林改户发展林下经济,都迫切需要符合实际的经营项目与技术支持。伊春林区野生榛资源丰富,进行野生榛林改培,成本低,收入可观,是林区职工增加经营林地收益的好方法。  相似文献   

8.
Climate change is a threat to the stability and productivity of forest ecosystems throughout the Asia-Pacific region. The loss of forests due to climate-induced stress will have extensive adverse impacts on biodiversity and an array of ecosystem services that are essential for the maintenance of local economies and public health. Despite their importance, there is a lack of decision-support tools required to evaluate the potential effects of climate change on Asia-Pacific ecosystems and economies and to aid in the development of regionally appropriate adaptation and mitigation strategies. The project Adaptation of Asia-Pacific Forests to Climate Change, summarized herein, aims to address this lack of knowledge and tools and to provide support for regional managers to develop effective policy to increase the adaptive capacity of Asia-Pacific forest ecosystems. This objective has been achieved through the following activities: (1) development of a high-resolution climate downscaling model, ClimateAP, applicable to any location in the region; (2) development of climate niche models to evaluate how climate change might affect the distribution of suitable climatic conditions for regionally important tree species; (3) development and application of forest models to assess alternative management strategies in the context of management objectives and the projected impacts of climate change; (4) evaluation of models to assess forest fire risk and the relationship between forest fire and climate change; (5) development of a technique to assess ecosystem carbon storage using LiDAR; and (6) evaluation of how vegetation dynamics respond to climate change using remote sensing technology. All project outputs were developed with a focus on communication and extension to facilitate the dissemination of results to regional forest resource managers to support the development of effective mitigation and adaptation policy.  相似文献   

9.
本文论述了木材检验中造材后量材改锯中存在的问题。如原木的一断面腐朽为薪材,而另一端为优良断面的木材,如何进行量材改锯等等。并提供了木材改据参考一览表。  相似文献   

10.
毛竹人工林生物量结构变化研究   总被引:1,自引:0,他引:1  
对会同县经营10年的毛竹人工林林分生物量结构变化进行研究,结果表明:人工竹林不同龄级、径级、枝下高级和不同密度的生物量分配,81.2%生物量分配于1~7年生幼龄、壮龄、中龄竹;83.4%生物量分配于胸径11~15 cm之内;90.7%的生物量分配于枝下高7~11 m之内;86.2%生物量分配于立竹4 500~9 000株/hm2的林分之内,其中立竹4 500~6 750株/hm2的中密度林分,群体和个体生物量都表现出较高的水平。试验竹林垂直总生物量和地上、地下生物量比对照竹林分别增多1.81倍和1.97倍、1.56倍,地上与地下生物量之比为1.774∶1,经济系数为0.501,生物量从大到小的排序,地上部分为秆﹥枝﹥叶﹥凋落物﹥竹箨﹥退笋,地下部分为鞕根﹥竹鞕﹥竹蔸﹥竹根﹥死鞕。  相似文献   

11.
This paper examines how foresters have adapted to important supply and demand driven shocks in the last century that affected timber prices and forest investments. Many of the adaptations that foresters made to changing economic conditions will be the same types of adaptations that society will need foresters to make in the future in order to adapt to climate change. These include changing rotation ages to adapt to shifting disturbance conditions, increasing intensification of management in response to dwindling old growth stocks, movement of species across regions to find better growing conditions, among other things. The paper presents results of an integrated assessment of climate change impacts in forestry and shows how projected future changes for the next century are well within the historical context.  相似文献   

12.
13.
作者对住宅设计室内空间的变化,提出了自己的观点,并阐明这也是目前住宅设计中急待解决的问题。  相似文献   

14.
为更好地实现八英庄林场森林资源的优化配置,以河北省木兰围场国有林场管理局八英庄林场2010年和2015年2期地形图、遥感图像及二类调查数据为基础,运用ArcGIS10.0和Fragstats4.2软件,对砬沿沟流域森林景观变化进行分析。砬沿沟流域按一级景观分类划分,斑块类型共5类,有林地斑块面积由473.95hm~2增加为500.88hm~2,其他斑块面积相对减小;有林地的景观形状指数、散布与并列指数减小,分别由3.008 1、59.106 6降为2.481 6、49.060 4;景观多样性由0.426 9减小为0.233 4,说明各斑块的聚集程度有所增加,各斑块之间的连通性有所提高。砬沿沟流域按二级景观分类划分,在有林地类型中,2010年和2015年斑块类型都为5类,到2015年山杏林斑块消失,新增云杉林斑块;2010至2015年华北落叶松林斑块面积、斑块景观形状指数均增加,山杨林斑块面积、斑块景观形状指数均减小。砬沿沟流域森林景观香农多样性指数由1.602 7降为1.389 2。除去一级景观分类中有林地斑块破碎度减小,其他无论是一级景观分类还是二级景观分类,各斑块破碎度都有不同程度的增加,说明近5a一级、二级斑块在总数上有所增加,并且增加的斑块相对独立,并不连续。  相似文献   

15.
林口林区次生林植苗改培技术初探   总被引:1,自引:0,他引:1  
针对黑龙江省林口林区天然次生林较差的林分状况,该地区选择红松和红皮云杉作为主要树种进行改造、更新.文中通过对改培样地的调查,介绍了在不同光照、坡度、坡位条件下,改培树种的生长状况,从而提出较好的改造方案和措施.  相似文献   

16.
Buchmann N 《Tree physiology》2002,22(15-16):1177-1184
There are many ways of studying forest responses to global change. Most current national and international programs focus on net gas exchange of the terrestrial biosphere and are typically interdisciplinary, multi-scale projects. Key objectives of these programs are surprisingly similar to those of classical plant ecophysiology studies, i.e., to explore functional relationships of plant or plant community responses to environmental change. Thus, common research questions that link plant ecophysiology to ecosystem functioning can be identified for both research communities, promising complementarity and synergism for joint research projects. Although some well-established ecophysiological relationships, such as light responses or stomatal limitations of photosynthetic gas exchange, are currently employed in many ecosystem-scale net flux studies for gap-filling or modeling, only 14% (n = 27) of all eddy covariance flux studies in forests (n = 196; published between 1992 and April 2002) include plant ecophysiological measurements (n = 24) or biomass and growth estimates (n = 8). Generally, emphasis is on CO2 exchange measurements at various scales (foliage, shoots, branches; n = 14) and water relations measurements (n = 11). These measurements do not fully support the typical parameterization of stand and regional models, which often need information on canopy architecture and nitrogen nutrition. By means of a complementary research approach, valuable information can be acquired that is unobtainable by means of a single approach. This additional information is important for the identification of underlying biotic and environmental drivers, for the regulation of net ecosystem fluxes and their partitioning, and the independent validation of measured net ecosystem fluxes. Thus, combining micrometeorology and ecophysiology at flux sites is strongly recommended for ecosystem functioning studies.  相似文献   

17.
大兴安岭林火迹地景观变化研究   总被引:3,自引:0,他引:3  
孔繁花  李秀珍  尹海伟 《林业研究》2004,15(1):33-38,J002
大兴安岭地区是中国非常重要的林区,也是容易发生林火的地区。1987年6月5日发生的一场大火,使1.33?06公顷原始森林被毁,并产生了不同火烧强度的森林景观斑块。本文以图强林业局的两个林场作为典型区(124°05′-122°18′E,53°34′-52°15′N),通过绘制和比较1987年和2000年数字化的森林组分图,分析了火后森林景观的变化情况。本文将森林覆被类型分为12类,针叶林、阔叶林、针阔混交林、灌木、苗圃、采伐迹地、火烧迹地、农用地、沼泽、水域、建筑用地和荒草地。通过研究,得出以下结论:1)林火迹地已几乎全部演替为其他森林景观类型,林火迹地主要是通过自然演替成为阔叶林,其次是通过人工演替成为针叶林,其余的则大部分演替为沼泽和荒草地。2)研究区森林覆盖率由1987年的47.6%变为2000年的81.3%。为了今后林业可持续发展与管理,本文提出了加强防火意识和注重树种多样性培育等对策。图3表3参11。  相似文献   

18.
Recently, it is documented that bamboo (Mousouchiku:Phyllostachys pubescens Mazel) invasion deteriorates ecological and/or landscape diversity. In order to investigate the ecological effects on forest-floor arthropods caused by bamboo invasion, we compared the myrmecofauna among broadleaf forests, bamboo-broadleaf mixed forests, and bamboo forests in Hiroshima City and its vicinity. Myrmecofauna in bamboo forests were more impoverished than in broadleaf forests. Myrmecofauna in the mixed forests, however, were similar to that in broadleaf forests in both species diversity and species composition. The change in myrmecofauna may occur relatively late after the initial bamboo invasion.  相似文献   

19.
20.
Daxing'an Mountains was one of the most important forest areas in China, but it was also an area which was prone to suffering forest fire. The catastrophic forest fire that occurred in Daxing'an Mountains on May 6, 1987 devastated more than 1.33×106 hm2 of natural forests, which leaded to the formation of some mosaic areas with different burn intensities. Two forest farms of Tuqiang Forest Bureau (124°05′–122°18′E, 53°34′–52°15′N) were chosen as a typical area to analyze the post-fire landscape change by drawing and comparing the two digital forest stand maps of 1987 and 2000. The landscape lands of forest were classified into 12 types: coniferous forest, broadleaf forest, needle-broadleaf mixed forest, shrub, nursery, harvested area, burned blanks, agricultural land, swamp, water, built-up, grass. The results showed that: 1) The burned blanks was almost restored, some of them mainly converted into broadleaf forest land during the process of natural restoration, and coniferous forest land by the artificial reforestation, and the others almost changed into swamp or grass land; 2) The proportion of forest area increased from 47.6% in 1987 to 81.3% in 2002. Therefore, a few management countermeasures, such as the enhancing people's consciousness of fire-proofing and constructing species diversity, were put forward for forest sustainable development. Foundation item: Under the auspices of the National Science Foundation of China (No. 30270225, 40331008) and the Chinese Academy of Sciences (SCXZY0102). Biography: KONG Fan-hua (1975-), female, Ph.D. candidate of Hiroshima University in Japan, specialized in Landscape Ecology. Responsible editor: Zhu Hong  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号