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891.
892.
分析了青田县万山片在森林资源管护上存在的林木凭证限额采伐制度实施难度大、木材流动秩序混乱、非法加工普遍、森林火灾的发生趋势上升、重砍轻造采伐迹地递增、林政管理队伍力量簿弱的现状,进一步揭示了所形成的原因,最后提出了继续深入开展学习贯彻执行宣传林业政策法律法规、增强基层政府领导的林业法制观念、抓好森林资源管理、加强林政资源队伍建设等措施。  相似文献   
893.
广州市近郊帽峰森林公园的基本功能定位为生态、科研、游憩和服务。据此提出了突出自然野趣,以人为本,促进人与自然的融合、沟通为内容的规划构想。  相似文献   
894.
Traditional fallow systems of Latin America have not been extensively studied from either a socioeconomic or biophysical viewpoint. Only in the past decade have some of these systems — modified shifting cultivation in the Amazon, the bracatinga (Mimosa scabrella) fallow of southeastern Brazil, the babassu (Attalea spp.) system of the Amazon margins, and short bush fallows mostly for Phaseolus bean (the so-called frijol tapado) — received any attention. Over the past century, traditional cultivators have adopted several legumes such as Mucuna spp., Lathyrus nigrivalis, Canavalia spp., and Senna guatemalensis as green manures or managed fallows in food crop production systems, which have recently been the object of studies by social and biological scientists. Longer, monospecific fallows involving woody legumes have been studied to varying degrees. The legumes include Senna guatemalensis, Mimosa tenuiflora, and Gliricidia sepium. Systems in which crop production is alternated with animal grazing of secondary vegetation include the caatinga of Northeast Brazil, the espinales of Chile, the matorrales of northern Mexico, and the chaco of Argentina, Paraguay, and Bolivia. A classification is proposed depending on the nature of the species (woody or nonwoody) and their composition (mono- or multispecies) and land management (burned or not). Much work is still needed in more complete characterization, determination of economic importance and potential, understanding the relationships among components, studies of nutrient cycling, and verification of the effects of shorter fallow periods of these systems.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   
895.
With structural changes in agriculture, new types of forest owners have become increasingly important. This article develops an empirically-based typology of forest owners in Austria. Based on a representative survey and by means of cluster analysis, seven types of forest owners are identified. These types form a sequence, ranging from forest owners with a strong agricultural background to forest owners with no agricultural background at all. The latter exhibit markedly different behaviour in various respects, e.g. in their interest in forest-related information. The increasing number of ‘new’ forest owners raises important questions for forest policy, especially how policy instruments can reach these owners and how extension services can address them.  相似文献   
896.
索系是指索道各工作索相互关联的配置系统,主要包括索道各工作索相互关联而成的各种承载方式、起重方式、牵引方式和落勾方式。而索道的起重方式基本上包含了索道的承载方式,牵引方式基本上包含了落勾方式。本文根据索道工作索的总根数及其起重方式和牵引方式,对林用索道的索系进行了分类,并编制了代号。  相似文献   
897.
898.
The effects of anthropogenic disturbances on forest structure and plant diversity of secondary forest ecosystems were evaluated based on the classification by site factors in the montane regions of northeastern China. Forty-five sample plots containing 720 sub-plots of overstory species (8 m × 8 m), 1,440 quadrats of understory species (2 m × 2 m), and 1,440 quadrats of herbaceous layer species (1 m × 1 m) were clustered into five groups (G1, G2, G3, G4 and G5) by site variables with Hierarchical Cluster Analysis. Meanwhile, the disturbance levels corresponding to the five groups were determined according to the factors influencing human disturbances (D0-G2, D1-G1, D2-G3, D3-G5, and D4-G4). Species diversities of overstory, understory, herbaceous layer and overall species were evaluated using species number, Margalef index, Pielou index, Shannon–Wiener index, and Simpson index; and β-diversities (Whittaker index, Cody index). Basal area of stands exhibited a decreasing trend along the disturbance level due to a gradual increase in the extraction of timber by the human disturbances. The indices of species diversity suggested that overstory and understory species were distributed evenly among the groups or disturbance levels. There were no absolutely dominant tree species in the secondary forest ecosystems. The differences in site factors and the current disturbance intensities were not intense enough to lead to loose changes in overstory and understory species. The species diversity indices exhibited the maximum values at D3 (G5) for herbaceous layer species; this may suggest that the current disturbance intensities were intense enough to lead the changes of herbaceous layer species. Three rare and endangered species (Juglans mandshurica, Fraxinus mandshurica and Acanthopanax senticosus) were found within the secondary forests. These rare and endangered species appeared in each clustered group or disturbance level, which suggested that the current disturbance intensity in the study area was not strong enough to influence the distribution of rare and endangered species. The current disturbances in the secondary forests may not lead to a decrease in stability and complexity of the overstory and understory species, but the higher disturbance level may be intense enough to change the habitat fitness for the herbaceous species. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized authors.  相似文献   
899.
Nontimber forest product harvesting in the Pacific Northwest is neither a new activity nor a disappearing relic of the pre-industrial era. Though the emphasis may have shifted from subsistence to commercial and recreational pursuits, harvesting and harvesters of wild species are still widespread throughout the region. Hundreds of businesses and thousands of harvesters earn part or all of their income from the harvests. Every year thousands of pounds and hundreds of nontimber forest products valued in the hundreds of millions of dollars are harvested from regional public and private forests. This harvesting of a large diversity of species represents a considerable subset of the overall terrestrial biodiversity in Pacific Northwest forests. Despite widespread extraction, little investment in research, planning, or basic inventorying and monitoring has been done on nontimber forest products. Without better information, land managers will be increasingly unable to make informed decisions on how to manage nontimber forest product biodiversity sustainably as demand for products increases.  相似文献   
900.
INTRODUCTIONWith the implementing of the Natural ForestryProtection policies in China, the plantation forestry willplay a much larger part in meeting the demand for wood.But the plantation wood, especially Poplar and Fir, havecommon properties of soft structure, low density andpoor processing. Generally speaking, these propertiescan be evidently improved by compressing. MasafumiInoue et al. (1991a, 1991b, 1990) had studied thesurface compression of coniferous wood. Their studiesshowed …  相似文献   
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