四川省薪材资源评价及分区

薪材在农村能源中占有重要地位,目前全省薪炭林面积71万公顷,森林能源每年合理提供量为904.5万吨标准煤,而实际消费量为1895.8万吨标准煤,消费量是合理提供量的2.1倍,薪材供需矛盾尖锐。预测2000年全省薪材需求量为2184.8万吨标准煤,尚需发展30万公顷薪炭林。为了宏观指导农村能源建设,在分析现状和进行需求预测后,将全省薪材资源划分为4个大类和13个类型区,分别阐述了各区特点和解决途径,最后对我省农村能源发展的重点和措施提出了指导性原则。     

Foresters' beliefs about farmers: a priority for social science research in social forestry

This study suggests that one of the most productive (and most neglected) uses of social science research in forestry development projects is to examine foresters' beliefs regarding rural peoples. This suggestion is illustrated with data from the Forestry Planning and Development Project, Pakistan's first nation-wide social forestry project.The operational component of this project, intended to assist small farmers to cultivate trees on their farmlands, ran into immediate difficulties. Many of the foresters involved insisted that small farmers were simply not interested in tree cultivation. A comprehensive base-line study subsequently was carried out to examine the validity of this belief. The results of this study (confirmed by the subsequent experience with the project in the field) varied markedly from the foresters' beliefs.While many of the foresters believed small farmers were opposed to having trees on their farms and would not agree to plant trees under the project, most farmers already had trees on their farms and expressed interest in planting more; while many foresters believed farmers would only be interested in planting large blocks of market-oriented exotics, most farmers requested small plantings of multi-purpose native trees; while many foresters believed farmers would plant trees only for market sale, most farmers requested trees to meet household needs for fuel and timber; and while many foresters did not think that increasing supplies of fuelwood could reduce the burning of dung, all of the evidence provided by the farmers suggested that it would.The disparity between farmer reality and forester belief is attributed to failures on the part of both foresters and social scientists — failure by foresters to distinguish their non-empirical beliefs about farmers from their empirically-based knowledge of trees, and failure by social scientists to recognize the belief systems of foresters as a legitimate and important object of study. Their study comprises three parts: finding out what the foresters think the farmers want, finding out from the farmers what they actually want, and then analyzing and explaining the differences.     

Spatially Explicit Evaluation of Local Extractive Benefits from Mangrove Plantations in Bangladesh

Mangroves worldwide provide a wide range of ecosystem services utilized directly and indirectly by local peoples. Between 1966 and 2001, Bangladesh established approximately 148,000 ha of mangrove plantations in coastal areas within the Barisal and Chittagong Divisions. Though erosion and human encroachment and conversion have removed over two-thirds of these stands, the Forest Department has continued to undertake new plantation activities.

To investigate how and to what degree people directly utilize these mangroves, I conducted 340 household surveys across eight coastal villages located in close proximity to established plantations. The predominant direct use of the mangrove plantations by local rural communities is the extraction of detritus and nonmain stem material (e.g., limbs, leaves) for combustible fuel. This study uses household foraging distances to estimate and map net value densities based on reported market prices of extracted goods. The average extractive value of mangrove plantations is Tk 2,300 ha^?1 yr^?1, ranging among the villages from 300 to Tk 27,400 ha^?1 yr^?1, with values concentrated closer to the village. Cost-benefit analyses suggest that direct use values alone have justified the establishment and management of previously planted stands. However, other indirect values must be taken into account if these areas are to merit additional plantations.     

An evaluation of the Acacia albida-based agroforestry practices in the Hararghe highlands of Eastern Ethiopia

Growing Acacia albida as a permanent tree crop, on farmlands with cereals, vegetables and coffee underneath or in between, is an indigenous agroforestry system in the Hararghe highlands of Eastern Ethiopia. However, there is practically no systematic record or data on the merits and benefits of this practice.The paper presents the results of an investigation into the effects of the presence of A. albida on farmlands on the yield of maize (Zea mays L.) and sorghum (Sorghum bicolor L. Moench). Twenty seven plot pairs each consisting of one plot underneath the A. albida foliage cover and the other in the open, away from the tree-on farmers' fields, in a 40 km radius around the Alemaya College of Agriculture, were sampled and the yield components analyzed. A statistically significant increase in crops yields by 56% on average was found for the crops under the tree canopies compared to those away from the trees. This increase was caused by the improvement in 1000 grain weight and number of grains of plants under the tree, indicating that the trees enhanced the fertility status of the soil and improved its physical conditions in terms of crop growth.Additional benefits from the A. albida trees include supply of fuelwood and fodder. Quantitative estimates of these outputs as well as their monetary values are presented in the paper. However, in order to realize these benefits to a discernible extent, higher stand densities of the tree than at present are required.Based on an enquiry about the farmers attitude towards A. albida, the prospects for an extension of this promising agroforestry technique are discussed against the background of the state and trends of development of agriculture in the area. It is surmised that despite some shortcomings like the relatively slow and highly variable growth of A. albida and a conflict with the spreading cultivation of Ch'at (Catha edulis Forsk.), the prospects of extension of this technique are good. It is recommended that its propagation should be incorporated into the programmes of the extension agencies of the various governmental agencies concerned with land use.     

Marketing constraints for Eucalyptus from farm lands in India

During the early eighties farmers in north-west India planted Eucalyptus on a massive scale for sale as poles and pulpwood. However, after 1986 farmers in this region have almost stopped growing Eucalyptus, as their experience with its marketing was not a happy one. The pole market got saturated, paper mills did not pay a remunerative price, and fuelwood prices were low and uneconomical. More important, because of legal restrictions on the transport and sale of wood, and other institutional factors, the gap in the farmgate price and the consumer price remained very wide. Wood markets have, on the whole, exploited the farmers, rather than helped them. Due to this, the short period of flirtation with tree crops seems to be over for at least resident farmers in those very areas in north-west India where they had so enthusiastically planted Eucalyptus in the early 1980s.Abbreviations BDO Block Development Officer - Headloaders poor people who collect firewood on their heads from forest lands for consumption and sale - m ha million hectares - Rs Indian Rupee 16 Rs = 1 US Dollar in 1989 - panchayat elected village organisation - pradhan village chief On study leave from the Government of India to the Oxford Forestry Institute, South Parks Road, Oxford, OX1 3RB, U.K. Present address: 17 Ponnappa Road, Allahabad 211001, India     

Acacia cyanophylla for forage and fuelwood in North Africa

Forage and wood yield of Acacia cyanophylla, also known as Acacia saligna, was studied in a 300–400 mm precipitation zone in Tunisia. Yields were measured during and after drought. This short (2–8 m) evergreen leguminous tree is used as a forage drought reserve in frost free regions where mean annual precipitation exceeds 250 mm. The standing crop of leafy forage builds up year after year for at least four years or until the tree is cut. It rapidly regrows after cutting from coppice shoots. The leaves provide high protein forage for sheep and goats during the long dry summer season typical of the Mediterranean climate as well as emergency forage during drought. The tree is used to stabilize moving sand dunes, and as a windbreak to protect cropland. It also provides fuelwood and increasaes soil nitrogen by fixation. The need for supplemental irrigation during establishment is a major constraint. Research in the 350 mm precipitation zone of Tunisia found 3.2 year old trees to yield over 1400 kg of forage standing crop per hectare after a severe drought. Trees harvested at 2.5 years of age in May, during the worst drought in over 30 years, yielded a standing forage crop of 724 kg per hectare. Forage regrowth 8 months after cutting and 4 months after rains returned was 700 kg/ha. The forage standing crop for trees harvested only once during the 3.2 year period was double the amount of forage regrowth from trees harvested the previous year, but mean annual forage yield similar. This demonstrates that it is possible for forage to be conserved as a living forage reserve for later use during drought. Total wood yield was only 1621 kg/ha for trees cut twice compared to 3683 kg/ha for trees cut only once. Annual cutting will substantially reduce the amount of forage available during drought and reduce the production of fuelwood. It may also reduce the vigor, productivity and life of the tree. Acacia cyanophylla alley cropped on cereal farmland can protect the soil from erosion, protect the associated crop from wind damage, fix nitrogen, provide fuelwood and provide a reserve of high quality forage for use during drought. This work was supported by the Government of Tunisia and the U.S.A.I.D. Tunisia Range Development and Management Project (664-0312.8).     

直干桉薪炭林萌发试验研究

对玉溪市直干桉薪炭林进行不同伐桩高度，不同砍伐方式，不同季节砍伐的试验研究表明，在玉溪地区经营直干桉薪炭林，砍伐可以提高薪炭林的产薪量，砍伐过的林分产量比对照提高１２．６倍，最高可达１６．９倍；伐桩高度在３０ｃｍ最好，砍伐方式以刀砍为主，伐后的产薪量也比锯的稍好；冬季砍伐比春季砍伐效果明显，平均树高可提高４８％，最大为５６％；采伐季节在林木休眠后，萌动前进行。该研究对指导玉溪地区经营桉类薪炭林具有重要意义。     

Fuelwood Resources and Forest Regeneration on Fallow Land in Uganda

Abstract

East African forests have been largely converted to agriculture. The remaining forests hold many endangered species but are threatened by the heavy local demand for fuelwood. Here we evaluate fallow land in western Uganda as an alternate fuel source to diverse forests. We quantify the regeneration process on fallows, calculate tree bio-mass increases, and measure grass and woody herb biomass over 44 months. The biomass values we measured were typical or slightly below the average from 11 studies elsewhere in the tropics. Variation in biomass between our neighboring study sites exceeded that between sites on different continents, indicating the sensitivity of vegetation regeneration to local land use. Tree regeneration was extremely slow (0.46 g/m²/year); however, the woody herbs and grasses on a 4 year old fallow of ～0.5 ha can provide much of a family's domestic fuel. Fallow land is generally abundant in western Uganda and can partially alleviate pressure on forests for domestic fuels. Fallows cannot however provide the trees demanded by charcoal, brick, and gin manufacturers. In the future, conserving forests while meeting fuelwood demands will require improving local land tenure security, enhancing the productivity of cultivated and abandoned land, promoting more efficient stoves, stills and kilns, and curtailing illicit, inefficient charcoal manufacture.     

干旱区土地利用和土壤改良及植被恢复方式对沙地养分的恢复效应

为研究干旱区土地利用、土壤改良和植被恢复方式对沙地养分的恢复效果,在乌兰布和沙漠东北缘开展试验研究。研究表明,土地利用方式和人为合理的经营活动对沙漠化土地肥力的恢复和提高有较大影响,在农业耕作制度中,其改土培肥效应以草田轮作最高,农作物套种次之,农作物单种最低;在荒漠沙地上种植农作物较果树更有利于保护土壤生态环境;在荒漠沙地上造林,应以防护林为主,不宜营造大规模杨树速生丰产林;在沙地上营造灌木薪炭林,可起到改良贫瘠沙地的功效;在沙地上种植沙打旺、草木樨和苜蓿均可有效的提高沙化土地肥力,以沙打旺效果最好,草木樨次之,苜蓿最差;在围栏封沙育草中,不同植物群落类型对沙地土壤改良效果有所不同,多植物群落优于单一植物群落。土壤氮磷比由高到低依次排序为白刺＋沙蒿＞沙蒿＋沙竹＞沙蒿＞沙竹＞小花棘豆＋沙蒿＞白刺＞小花棘豆,土壤氮磷比的高低主要取决于氮素水平。     

以芳香油和薪材为最终产品的桉树幼林地上部分生物量研究*

在2年生的桉树引种试验林内,对蓝桉和新引种的5种其他桉树的地上部分生物量进行了测定。研究发现,当轮伐期为2年时,不同桉树的芳香油和薪材收获量差异显著,而同一树种的芳香油和薪材产量在不同造林密度之间无显著差异。史密斯桉和贝克桉的芳香油和桉树脑含量均高于蓝桉,是生产桉树芳香油和薪材的优良树种,在我国亚热带地区有进一步试验和推广的价值。