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《Forest Ecology and Management》2006,233(1):21-35
To determine annual litter production of regenerating forest areas in the Tigray highlands of northern Ethiopia monthly litter production was monitored over a two-year period in areas with varying degree of vegetation cover restoration. Total annual litter production varied from 30 to 425 g m−2 and increased significantly where areas were closed for a longer time. Litter production was depending on vegetation cover through an exponential relation and was influenced also by soil fertility. Leaf litter typically constituted between 70 and 85% of total litter production, while contributions of woody and reproductive litter varied according to species composition. Strong seasonality in litterfall was explained by pronounced seasonal variation in rainfall. Standing crop of litter built up once an area was closed for grazing, increasing from around 20 g m−2 in degraded grazing lands to nearly 600 g m−2 in an old exclosure. Litter accumulation was mainly determined by litter input, but was also influenced by litter quality, species composition and microclimate development in the restoring forest areas. A detailed study of nine dominant shrub and tree species revealed three distinct litter production patterns, corresponding to drought-deciduous species, evergreen species and (semi-)evergreen Acacia species respectively. 相似文献
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本文通过对我省森工经济现状的分析.从企业的经济管理体制,经营机制,发展林业多元经济培植新的经济增长点等方面。提出振兴和繁荣龙江森工经济的措施与对策。 相似文献
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Admixing broadleaved to coniferous tree species: a review on yield, ecological stability and economics 总被引:2,自引:1,他引:1
Thomas Knoke Christian Ammer Bernd Stimm Reinhard Mosandl 《European Journal of Forest Research》2008,127(2):89-101
For several reasons the conversion of mono-species into mixed-species forests is presently a major concern of forest management and policy in Central Europe. Although it is possible to show a clear trend in favour of mixed-species forests, private forest owners and some forest economists have often not favoured mixed forests, assuming that they are less profitable. The trend towards mixed forests seems mainly for ecological reasons, while sound economic analysis of mixed forests is still rare. Based on this background the objective of the study is to answer the following four questions: (1) Does the yield of mixed-species forests differ from that of pure forests? (2) Does the mixing of tree species influence the ecological stability of forests? (3) Is the economic value of a mixed forest less than that of a monoculture? (4) How do forest economic models integrate the findings on yield and ecological stability of mixed forests? To answer these questions a literature review was conducted on the possible impacts of mixed-species forests. In comparison to pure stands a greater yield is not necessarily given in mixed stands. Yet, mixed-species stands are better able to compensate disturbances than monocultures. Moreover, there is substantial evidence that mixed-species stands are more resistant against biotic and abiotic disturbances. Applying an extended forest economic model, it was possible to demonstrate that mixing large blocks of native broadleaf species into pure conifer forests may lead to a significant reduction of financial risk. From a risk-averse perspective the economic value of a mixed-species forest may thus be greater than that of a mono-species forest. Yet, it became clear that forest economists do not often integrate the research findings on yield and ecological stability of mixed stands in modelling, but rather apply simple bioeconomic modelling. Moreover, in the context of mixed forests economists also largely ignore even classical financial approaches, which consider risk and risk preferences. We concluded that forest economics has to close substantial research gaps. Firstly, the knowledge of how to integrate biophysical properties of mixed forests in bioeconomic modelling is still an open question. Secondly, forest economists have to adopt the modern approaches of financial theory and management science to value mixed forests. 相似文献
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Stem volume equations were fitted for Cupressus lusitanica in Gergeda Forest, Ethiopia using six different established equation forms. A total of 260 trees were measured for their diameter at breast height (D), total height (H?)and stem volume using destructive sampling methods. The data set was randomly divided into equal size for equation development and equation validation. Five fit statistics comprising of the fit index, root mean square error, bias (ē?), absolute mean deviation and coefficient of variation were used to evaluate the performance of each equation. Among the different equations, the Schumacher and Hall function of the form V = b1Db2Hb3 (model 5), which estimates volume (V?) using diameter at breast height and total height as predicting variables, performed best and was then fitted to the combined data set for prediction of volume over-bark of C. lusitanica in Gergeda Forest. Overall, volume equations with two independent variables (D and H?) performed better than those with only one variable (D). The equations developed in this study can provide forest managers with accurate estimations of stem volumes for C. lusitanica in Gergeda Forest. 相似文献
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Exclosure is a method of rehabilitating degraded lands by protecting them from the interference of animals and from human encroachment, and is used to regenerate native vegetation as a way to reduce soil erosion, increase rain water infiltration and provide fodder and woody biomass in degraded grazing lands. Therefore, we studied woody plant structure, diversity and regeneration potentials in 5- and 10-year grazing exclosures in comparison with open grazed sites in a semi-arid environment. Data on species diversity, abundance, structure, basal area, frequency, density, and regeneration status were collected from 270 sample plots. Forty-one woody species representing 20 families were identified, with 18, 28 and 38 species found in open grazed areas, and in 5- and 10-year grazing exclosures, respectively. The 10-year grazing exclosures had a higher (P < 0.05) species richness and plant densities compared to the 5-year grazing exclosures and the open grazed areas. The population structure and regeneration status of woody species in both grazing exclosures showed an inverted J-shape, indicating a healthy regeneration status, whereas hampered regeneration was observed in open grazed areas. The establishment of grazing exclosures had positive effects in restoring woody plant diversity and improving vegetation structure and regeneration potentials of degraded grazing lands. 相似文献
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The Afromontane forests of Ethiopia have been under a serious degradation threat. Assessment of floristic diversity and species composition in Biteyu forest of Gurage mountain chain in the central Ethiopia was conducted to examine the pattern of forest structure. Thirty plots of 30 m×30 m were used to record the vegetation and environmental data using systematic sampling technique. The local name, plant scientific names, DBH, height,species abundance and percentage canopy cover of plant species were recorded. Shannon diversity index and Sorensen's coefficients was used for comparison among communities and similar forests in the country. Threats to the forest biodiversity in Biteyu were determined by counting cattle interference and wood stumps as disturbance indicators. Relative Euclidean Distance measures by using Ward's method(linkage) was applied for cluster analysis. Environmental variables were also recorded in each plot. Woody species population structure, basal area and importance value index were analyzed using spreadsheet programs. Data on species distribution and environmental variables in the forest were analyzed by canonical correspondence analysis. A total of 190 species in 154 genera under 73 families were identified. Twenty species were found to be endemic taxa to the Flora Area. Only three plant community types were identified from the cluster analysis due to the high human influence. The Sorensen's coefficient showed the resemblance of the Biteyu forest with other Dry Evergreen Afromontane forests in the country. Moreover, altitude and slope strongly affect the species composition and structure of Biteyu forest. Given the high anthropogenic influence, high endemism, high dependence of the local community on the forest resources, forest conservation and restoration measures should be done by stakeholders. 相似文献
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基于"3S"技术,采用总体蓄积抽样控制、小班调查、消耗量调查等方法,查清了师宗县各类土地面积和各类森林蓄积、林木和林地资源的种类、数量、质量,落实了森林分类经营区划,对调查数据动态变化进行了分析,提出了加强天然林保护、商品林多功能经营、发展林下经济和生态旅游等林业发展建议。 相似文献
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Mesfin Tilahun Roland Olschewski Christoph Kleinn Kindeya Gebrehiwot 《Forest Policy and Economics》2007,9(8):996-1005
In Ethiopia, environmental degradation leads to a reduction of forest areas with economically important tree species like Boswellia papyrifera. In an attempt to reverse this development and assist natural rehabilitation, closing degraded forest from free grazing, fuel wood collection and other interference is practiced in Tigray. Sustainability of this management will, among other things, depend on the resources' tangible benefits. This study aimed to determine and compare net benefits (in Ethiopian Birr (ETB) per ha) from the closed and open Boswellia papyrifera forestlands. Production and household surveys were carried out in Jijike and Siye tabias of Abergelle woreda in northern Ethiopia. Data on costs and benefits of frankincense production were collected from firms trading the product. Net benefits from forestlands and croplands were determined using the Net Present Value criterion. The estimated mean frankincense productions were 127 kg/ha/yr for closed forestland and 84.54 kg/ha/yr for open forestland. A significant difference (p < 0.05) was observed between per tree mean frankincense yield of closed and open sites. The average grass harvest from closed area was 2851 kg/ha/yr. The financial Net Present Values were 8622 ETB/ha for closed and 6468 ETB/ha for open forestlands. These values were by 4574 ETB and 2005 ETB higher than the sum of NPV from crop and crop residuals of a hectare of cropland in the study area of the two sites, respectively. Exporting frankincense could generate foreign exchange of 53.28 and 39.05 USD/ha/yr from closed and open sites, respectively. Rural households earn about 74% of the annual total revenue (ETB/ha) from closed and open area as wage for tapping and collecting frankincense and using of grass. Sensitivity analysis showed that managing degraded Boswellia papyrifera forestland as closed area always generates a higher NPV than the open one in case of changes in discount rate and prices of inputs and outputs. Thus, managing the forest through closed areas is a competitive land-use alternative and provides higher net benefits than both open forestland and agricultural croplands. 相似文献
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Solomon Tadesse Muluneh Woldetsadik Feyera Senbeta 《Journal of Sustainable Forestry》2013,32(8):604-622
ABSTRACTThis study examines a participatory forest management program and its impacts on forest conditions in Gebradima Forest, southwest Ethiopia. Vegetation data were collected from both participatory forest management (PFM) and nonparticipatory forest management (non-PFM) forest blocks. A total of 54 plots (27 from each forest block) measuring 20 m × 20 m were employed to collect species composition and structural data. Results indicated that a total of 51 different woody plant species (49 at PFM and 43 at non-PFM blocks), representing 31 families were recorded, with 41 species were shared for both forest sites. Species diversity and evenness were higher in the forest with PFM (H´ = 3.29, E = .85) compared to the forest without PFM (H´ = 2.97, E = .79). The overall mean values of tree/shrub and seedling density per hectare, diameter class (≤ 20 cm) were also significantly (p < .05) higher in PFM forest than non-PFM forests. However, no significant variations were observed in sapling density per hectare and basal area between the two studied forest blocks. It can be concluded that PFM had a positive effect on forest conditions compared with a similar forest without PFM. Hence, it is important to scaling up PFM in neighboring forests. 相似文献
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文章主要以吊罗山为例,通过与海南其它山地热带林区发展比较,探讨其适宜的“山地热带雨林”开发模式,从而提高吊罗山森林旅游的竞争力. 相似文献
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Tree planting on deforested farmlands, Sewu Hills, Java, Indonesia: Impact of economic and institutional changes 总被引:2,自引:1,他引:1
J. W. Nibbering 《Agroforestry Systems》1999,46(1):65-82
This paper analyses how farmers in the Sewu Hills, a limestone hill complex in Java, were led to grow trees on their holdings.
In the past, the area had been notorious for its deforestation, soil erosion and poverty. A historical analysis of change
in land use in the area bears out a number of factors that were conducive to these changes: increased crop productivity, depletion
of forest resources, better marketing opportunities for tree products, greater security of the trees and increased non-agricultural
employment opportunities. Tree planting campaigns launched by the government provided the population with important incentives,
establishing a critical mass of farmers adopting tree growing. Trees and their products have diversified, buffered and expanded
household economies in the Sewu Hills. Yet it remains to be seen whether the system can withstand the economic and social
pressures the area is facing today. A historical, multi-level analysis of land use adds considerably to cross-sectional studies
in understanding what causes farmers to grow trees on their fields.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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Tree planting by small producers in the tropics: A comparative study of Brazil and Panama 总被引:1,自引:0,他引:1
Forest regrowth is a notable phenomenon across the tropical forest latitudes. Such reforestation takes place in the wake of land abandonment, occurs cyclically in a rotational agricultural system, and may result from the deliberate planting of trees by farmers. Although less extensive than successional forest regeneration, tree planting by small farmers can have potentially important environmental impacts at both the site and global scale. This paper examines tree-planting efforts by small farmers in the tropical frontier regions of Panama and Brazil in order to gauge the magnitude of reforestation activities, and to identify factors that influence these efforts. This paper discusses the environmental regulations, forestry law, and tenure institutions in both countries, and performs a comparative analysis of reforestation efforts with information derived from household surveys (n = 356) and in-depth tree planting interviews (n = 35). Results from logistic regression are also presented. Our results show that tree planting occurs more frequently in Panama, which we attribute to greater external support in the provisioning of extension and materials and strong market incentives. We suggest that the proximity of the study sites to Panama City facilitates external support and market drivers. Finally, our results suggest that land tenure security is an influential determinant of reforestation activities in both countries.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
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珍贵树种是经济社会发展特需的战略资源,发展珍贵树种资源具有十分重要的意义。文章介绍了四川珍贵树种资源发展现状,分析了珍贵树种资源发展潜力,提出了珍贵树种资源发展原则和发展战略。 相似文献
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本文概要介绍了吉林省生态环境概况、林业建设成就与问题,论述了本省森林生态网络建设面临的任务及亟待解决的八个方面的问题,并对生物技术、信息技术、新材料技术及无公害森林保健技术在森林生态网络建设的应用前景进行了展望。参9。 相似文献
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我国森林采伐更新的发展与展望 总被引:4,自引:0,他引:4
本文根据国内外森林采伐更新的现状,各种采伐方式的利弊,试图探索一条适合我国国情的森林采伐更新方式和合理开发我国森林资源的新途径。 相似文献