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81.
从人的价值及行为形成机制出发,分析认为影响林业发展的核心因素是产权安排,目前我国林权制度存在所有权主体虚置、林地产权的各项权能边界不清、林地权属四至界限不清等问题.发展社会林业,必须界定出明晰的林业权能边界,强化林地使用权,保障四大权能. 相似文献
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关注林权:中国集体林政策研究国际研讨会综述 总被引:1,自引:0,他引:1
公共资源面对的挑战、风险与机遇受到国际社会的关注。文章以“国际公共资源研究协会第十届大会”为背景,对中国集体林研究课题的成果、相关国际会议内容及专家发言作了介绍。研究成果主要形成8个专题报告,国际会议分“中国集体林政策和法律框架的总体回顾”和“中国集体林与生态保护、公司 社区模式”两个部分展开,并形成了5点结论。 相似文献
84.
The North American long-term soil productivity experiment: Findings from the first decade of research 总被引:1,自引:0,他引:1
Robert F. Powers D. Andrew Scott Felipe G. Sanchez Richard A. Voldseth Deborah Page-Dumroese John D. Elioff Douglas M. Stone 《Forest Ecology and Management》2005,220(1-3):31-50
First decade findings on the impacts of organic matter removal and soil compaction are reported for the 26 oldest installations in the nation-wide network of long-term soil productivity sites. Complete removal of surface organic matter led to declines in soil C concentration to 20 cm depth and to reduced nutrient availability. The effect is attributed mainly to the loss of the forest floor. Soil C storage seemed undiminished, but could be explained by bulk density changes following disturbance and to decomposition inputs of organic C from roots remaining from the harvested forest. Biomass removal during harvesting had no influence on forest growth through 10 years. Soil compaction effects depended upon initial bulk density. Soils with densities greater than 1.4 Mg m−3 resisted compaction. Density recovery was slow, particularly on soils with frigid temperature regimes. Forest productivity response to soil compaction depended both on soil texture and the degree of understory competition. Production declined on compacted clay soils, increased on sands, and generally was unaffected if an understory was absent. 相似文献
85.
Muneto?HirobeEmail author John?Sabang Balram K.?Bhatta Hiroshi?Takeda 《Journal of Forest Research》2004,9(4):347-354
The effects of tree species on the dynamics of nutrient transformations during leaf-litter decomposition are not well understood
in tropical rain forests. To examine differences in the dynamics of C, nutrients, and organic constituents during decomposition
among tree species, the leaf-litter decomposition of 15 trees was assessed using a litter-bag method in a lowland tropical
rain forest in Sarawak. The dynamics of C was parallel to that of weight loss. The dynamics of nutrients were grouped into
three patterns. The dynamics of K was characterized by a high leaching loss in the initial stages, and that of Ca and Mg generally
showed a gradual decrease over the course of decomposition. The dynamics of N and P showed highly different patterns with
the weight loss, and was characterized by relatively higher remaining mass at the end of the experiment. The variations or
exceptions of nutrient dynamics among tree species were considered to be related to the initial concentration of each nutrient.
For the dynamics of organic constituents, water-soluble carbohydrates disappeared quickly at the initial stages, and acid-soluble
carbohydrates were the second fastest decomposing fraction; the decomposition of acid-insoluble residue (AIS) was the slowest.
The release of limiting nutrients (N and P) generally followed the disappearance of AIS, but was independent of the disappearance
of AIS when the initial concentrations of these nutrients were very low. 相似文献
86.
Bill Slee 《Small-Scale Forestry》2006,5(1):1-17
The nature of private forestry in the UK as an economic activity is changing, with increasing ‘public good’ demands being
placed on forest owners, with or without compensation from government. Although the motives for owning woodland are weakly
researched, it is evident that amenity and recreational interests rather than formal productive economic activity are a major
force in influencing woodland purchase and may well be a dominant force in woodland management over many parts of the UK.
Recent research suggests a need for recognition of the high value of the public goods and, in particular, recognition of their
high levels of spatial variability, whilst recognising that the public good — private good dualism is an oversimplification
of the actual situation. New policy instruments are currently being implemented in various parts of the UK by devolved governments,
and their capacity to both remediate market failure and address the needs of forest owners is considered. Their voluntary
character and the preferences of forest owners may seriously constrain the optimal delivery of public goods. Further, existing
policy instruments may be seen as insufficiently geographically targeted to areas where the greatest social benefits could
be anticipated from policy-induced improvements in public good values. 相似文献
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利用羧基丁苯胶乳对脲醛树脂胶粘剂进行改性,同时在脲醛树脂合成过程中加入一定数量的玉米淀粉等改性剂,进一步提高改性脲醛树脂的综合性能,降低生产成本。羧基丁苯胶乳改性脲醛树脂胶粘剂具有游离甲醛含量低、生产工艺简单等特点,生产出的胶合板的胶合强度和甲醛释放量均满足国家标准。 相似文献
90.
杨树材性成熟龄模型的建立及树体内幼龄材的分布 总被引:3,自引:0,他引:3
以小叶杨和北京杨的材性测定值(导管分子长度或木纤维长度或导管腔径)作为因变量,以年轮数作为自变量,建立材性成熟非线性模型,以此为依据讨论成熟龄问题,并对幼龄材在树体内的分布进行分析。导管分子长度、木纤维长度和导管腔径的成熟龄模型为应用分段回归分析方法拟合的二次方程和定数函数结合的非线性方程,方程的决定系数在0 85 7~0 991之间,并在0 1 %水平上达到显著。以导管分子长度作为材性指标,应用这个非线性模型分析的结果表明:材性成熟龄及幼龄材半径因树种、立地的灌溉条件不同存在差异。无灌溉北京杨6~1 0年达到成熟,幼龄材半径为5 2mm左右;无灌溉小叶杨2 4~2 9年达到成熟,幼龄材的半径为90mm左右;灌溉小叶杨1 3~1 5年左右达到成熟,幼龄材的半径为85mm左右。 相似文献