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《Forest Policy and Economics》2000,1(2):139-151
The economy of the Ukraine is in transition from a communist command-and-control to a capitalist system. In this paper, we describe the current state of its forest resources, the structure of its forestry and wood processing sectors, and the problems facing policy makers. While the forest sector should be, and still has the potential to become, an engine for economic growth, the combination of past exploitation and the slow pace of economic reform are major obstacles to implementing rational forest policies. Given the right economic incentives and appropriate forest policies, it may still be possible for the Ukraine to improve its future timber supply while enjoying environmental benefits from its forests. However, this requires economic and institutional reforms beyond the forest sector. 相似文献
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The contribution shows changes in the phosphorus and nitrogen status in long-term investigated spruce stands in the Lu?ické, the Jizerské and the Orlické Mts. on the border between the Czech Republic and Germany and Poland. During the 11 evaluated years, low phosphorus concentrations were measured, often below the deficiency limit 1.2 mg P/g, and an N/P ratio exceeding the optimal range (6–12), primarily in the second needle-year class. Values of an N/P ratio of between 12 and 18 in the Jizerské Mts. and of between 12 and 27 in the Lu?ické Mts. were discovered. A low phosphorus concentration below the 10 mg·kg?1 was also detected in the mineral soil horizon. Temporal changes of N/P ratio (increase) and of P concentration (decrease) in the needles are significant for the spruce stands that are in the Orlické Mts. In the Jizerské Mts. and the Lu?ické Mts., there is fluctuation during evaluated period without any clear trend. 相似文献
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R. Moreno-Ripoll R. Gabarra W. O. C. Symondson R. A. King N. Agustí 《Journal of pest science》2014,87(1):133-141
The whitefly Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) is a worldwide pest which has become one of the main pests in tomato crops. The predators Macrolophus pygmaeus (Rambur) and Nesidiocoris tenuis Reuter (Hemiptera: Miridae) and the parasitoid Eretmocerus mundus (Mercet) (Hymenoptera: Aphelinidae) have shown their efficacy at controlling B. tabaci populations when used as biological control agents. Intraguild predation (IGP) between natural enemies can affect their effectiveness at controlling pests. In the present study, the interaction of these three natural enemies and their effect on B. tabaci was studied on tomato plants by combining morphological observations and molecular analysis of trophic interactions. Under the conditions used in the present study, no IGP was detected between M. pygmaeus and N. tenuis by either counting dead predators or by PCR using prey-specific cytochrome c oxidase I primers. However, predation on B. tabaci decreased when they coexisted on the same plant, which could compromise the biological control of this pest. Although PCR analyses using E. mundus-specific primers showed predation on B. tabaci-parasitized nymphs in 27 % of M. pygmaeus and 17 % of N. tenuis, B. tabaci control was improved when both predators coexisted on the same plant with the parasitoid. The combined use of E. mundus and M. pygmaeus/N. tenuis is therefore recommended in order to improve B. tabaci control in conservation biological control strategies. 相似文献
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概述了近20年来国内外对催化α-蒎烯氧化反应过程的研究,重点分析了α-蒎烯氧化中催化剂的性能特点及产物分布规律,总结了过渡金属盐、氧化物、配合物、分子筛及杂多酸在α-蒎烯氧化中的催化作用,比较了催化活性及选择性的特点,并初步探讨了发展趋势.提出在已有的α-蒎烯氧化反应催化剂中,分子筛类催化剂在制备方法和工业化发展上有一定的优势,深入研究过渡金属化合物在α-蒎烯氧化反应的催化性能及调变方法,应是α-蒎烯氧化反应中值得重点关注的研究内容. 相似文献
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Indigenous management of tropical forest ecosystems: the case of the Kayapó indians of the Brazilian Amazon 总被引:1,自引:0,他引:1
Darrell Addison Posey 《Agroforestry Systems》1985,3(2):139-158
The Kayapó Indians of Brazil's Amazon Basin are described as effective managers of tropical forest, utilizing an extensive inventory of useful native plants that are concentrated by human activity in special forest areas (resource islands, forest fields, forest openings, tuber gardens, agricultural plots, old fields, and trailsides). Long-term transplanting and selection of plants suggest semi-domestication of many species. The overall management strategies of forest also includes many manipulated animal species (birds, fish, bees, mammals) utilized as food and game. Forest patches (apêtê) are created by Indians from campo/cerrado using planting zones made from termite and ant nests mixed with mulch: formation and development of these is briefly discussed, including the implications for new ideas concerning reforestation and campo management. Finally an integrative cognitive model is presented showing the relationships between variants of forest and savanna recognized by the Kayapó. Indigenous knowledge of subtle similarities between conceptually distinct ecological units in the model allows for the interchange of botanical material between microclimates to increase biological diversity in managed areas. It is suggested that indigenous knowledge is extremely important in developing new strategies for forest and campo/cerrado conservation, while improving productiveness of these ecological systems. Such knowledge is not only applicable for Amazônian Indians, but also has far-reaching implications for human populations throughout the humid tropics.This is a preliminary survey of indigenous management strategies that is generated as a part of the Projeto Kayapó , an interdisciplinary ethnobiological research project funded by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brazilian National Council for Scientific and Technological Development) and the World Wildlife Fund. I would like to thank Drs. Gerhard Gottsberger and Anthony Anderson for their assistance in collecting plants that are currently being identified to supply more complete data on Kayapó subsistence. I also wish to thank FUNAI (Fundaão Nacional do Índio) for their assistance and support, as well as FAB (Fora Aérea Brasileira) and VOTEC for providing some transportation to/from Gorotire, and the Unevangelized Field Missions for their assistance in providing communication and acquiring supplies. 相似文献
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We investigated the correlation of large fires([300 ha) from 1992 to 2013 within the borders of the Antalya Regional Directorate of Forestry using the Keetch–Byram drought index(KBDI). Daily KBDI values were calculated for each year, and values for the period before the year 2000 differed significantly from those after2000. After 2000(large fires occurred in 2004, 2006, 2007,2008, 2010, and 2013), when KBDI values increased, the KBDI, but not the number of fires, was inversely correlated with the natural log of the burned area(NLBA). While there were both high and low KBDI values when the NLBA was small, only high KBDI values were associated with high NLBA values. Particularly for logarithmic values of 4 and higher, KBDI values increased in parallel with increases in NLBA values. On the basis of a Mann–Whitney U test done in addition to a Pearson correlation test, we found that when the burned areas were grouped according to small and large areas, the KBDI could be used to distinguish the two groups. Using a conditional probability analysis, we found that 4th, 5th and 6th class KBDI values may lead to large fires at the 60 % possibility.Similarly, the possibility of large fires greater than the median burned area in any given 6 years was found to be48 %. In addition, while the mean value of KBDI is 390.51 for the period from May to September for these 6 years, it is 359.93 for the other years. Consequently, the area burned also increased as the KBDI classes(Class 0: 0–99, Class 1:100–199, Class 2: 200–299, Class 3: 300–399, Class 4:400–499, Class 5: 500–599, Class 6: 600–699, and Class 7:700–800) increase. 相似文献
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IntroductionAsagrowthmodelforanindividualtreeorforeststhnd,theChapman-RichardsFunction,anextensiontotheVonBertalanffy'sgrowththeory(Bertalanffy1957)embodiesallotherestablishedgrowthfunction.ThisfunctionhasbeenwideIyusedinforestrybecauseofitsflexibility,ac… 相似文献
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本文研究了长江三峡花岗岩地区林地土壤流失特性.结果表明由鳞片状面蚀导致的土壤流失量月分布与月降雨量的分布趋势基本一致,二者呈现出较为明显的线性相关关系.植物盖度≥0.70的林地土壤流失多集中发生在6~9月份,土壤流失量在5000t·km-2·a-1以下.盖度<0.7的林地土壤流失年内分布时间多在3~10月份,土壤流失量为500~6000t·km-2·a-1. 相似文献
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J. Paul McLean Olivier Arnould Jacques Beauchêne Bruno Clair 《Annals of Forest Science》2012,69(3):399-408
Context and aim
This study aimed to examine the effect of the tension wood G‐layer on the viscoelastic properties of wood.Methods
Tension wood and opposite wood samples were obtained from six French Guianese tropical rainforest species (Sextonia rubra, Ocotea guyanensis, Inga alba, Tachigali melinoni, Iyranthera sagotiana and Virola michelii); the tension wood of the former three of these species had a G‐layer, whilst the tension wood from the latter three had no G‐layer. Tensile dynamic mechanical analysis (DMA) was performed on green never dried wood samples in the longitudinal direction with samples submerged in a water bath at a temperature (30°C) and frequency (1 Hz) representative of the conditions experienced by wood within a living tree. Then, DMA was repeated with samples conditioned to an air-dried state. Finally, samples were oven-dried to measure longitudinal shrinkage.Results
Tension wood did not always have a higher longitudinal storage (elastic) modulus than opposite wood from the same tree regardless of the presence or absence of a G‐layer. For the species containing a G‐layer, tension wood had a higher damping coefficient and experienced a greater longitudinal shrinkage upon drying than opposite wood from the same species. No difference was found in damping coefficients between tension wood and opposite wood for the species that had no G‐layer.Conclusion
It is proposed that the different molecular composition of the G-layer matrix has an influence on the viscoelasticity of wood, even if a biomechanical gain is not yet clear. This study shows that rheological properties and longitudinal shrinkage can be used to detect the presence of a G‐layer in tension wood.17.
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