立地管理措施对2代6年生杉木林生长的影响

在福建省南平峡阳国有林场进行5种不同立地管理措施对29年生第1代杉木人工林采伐后营造的6年生第2代杉木人工林生产力影响的研究.结果表明:BL3(收获树干和树皮、加倍采伐剩余物)处理的6年生2代杉木林生长最好,其次为BL1(全树收获)和SB(收获树干和树皮,炼山)处理,BL2(收获树干和树皮,不炼山)和BL0(收获地上所有有机质)处理杉木生长最差.5种处理的第2代杉木林地位指数与第1代相比,BL3和BL0处理分别上升0.56和0.27,其余3种处理则有下降.BL1、SB和BL2处理地位指数分别比1代下降0.39、045和0.63.不同处理之间的差异均未达到统计上的显著水平.     

Nelder试验:大叶相思生长与密度、年龄的相关研究

自１９８７年以来，在贫瘠立地上开展了大叶相思Ｎｅｌｄｅｒ（放射型）密度试验，７年的研究结果表明，大叶相思的胸径、树高以及断面积×树高与初始单株面积的对数呈现向下的抛物线关系。在贫瘠立地上营造大叶相思，适当密植可促进林木胸径、树高的生长，以１ｍ×２ｍ或１．５ｍ×２ｍ等较小株行距为宜。对于不同初始密度的林分，随着年龄的增长，其林木生长差异最终呈现递减趋势。林分密度越大，其轮伐期亦越短。     

河北省太行山低山片麻岩区持续生态农业工程技术

为了搞好太行山低山片麻岩区的生态农业建设，促进经济发展，以生态经济学和系统论的理论为基础，采用一位试验与理论分析相结合的方法，确定了”旱，薄，蚀“的因素，研究出促进山区农业生态经济持续，协调，稳定发展的技术体系。     

炼山对二代5年生杉木幼林生长的影响

在福建南平对炼山和不炼山的第2代5年生杉木幼林生长进行对比研究,结果表明,2种处理杉木平均胸径年均生长量均在1.70 cm以上,平均树高年均生长量均在1.00 m以上;炼山处理杉木的生长量略高于不炼山,但它们之间的差异不显著。     

The relationship between length of fallow and crop yields in shifting cultivation: a rethinking

Rethinking the relationship between length of fallow and crop yields inshifting cultivation?The theory that a correlation between shortened fallow periods and yielddecline in shifting cultivation exists is questioned in this paper. Thisrelationship has been taken for granted, and because it shows that shiftingcultivation will break down under pressure, it has partly been responsible fornegative government views on shifting cultivation. Yield levels in shiftingcultivation are influenced by a wide range of biophysical, socioeconomic, andcultural factors and it is difficult to isolate fallow length as a singledetermining factor. A total of 330 studies were reviewed and fifteen withempirical data were chosen for in-depth analysis. Although most of the empiricalstudies support the theory, the data sets are often ambiguous and importantparameters are insufficiently taken into account. Several studies found norelationship between fallow length and yield, but these also lack information toverify the validity of the data. It is concluded that empirical studiesfocussing on this problem are needed to fully understand this relationship anddevelop feasible scenarios for the numerous attempts at modelling shiftingcultivation development. Moreover, the use of gloomy `breakdown' scenarios asjustification for improving shifting cultivation should be avoided.     

Cattle grazing under Pinus caribaea

An analysis is made of the animal stocking rate used in commercial Pinus caribaea plantations 2.5–8.5 yr old. Pines were planted at 2.5 × 2.5 m and programmed for clear-cut harvest at 10 yr rotations (pulpwood). Cattle grazing was introduced to reduce weeding costs.Stocking rate in 1983–1985 was 0.67 AU/ha/yr (AU = animal units 350 kg live weight). A quadratic model calculated using 1984 data (S = 0.0108 + 0.385A–0.0418A²) describes the relationship between animal stocking rate (S) and stand age (A 9.5 in yr).The model predicts a maximum of 0.89 AU/ha/yr at plantation age 4.5 yr. Grazing started at plantation ages 2.5 yr; no plantations older than 9.5 yr are grazed.     

On-farm research in a silvopastoral project: a case study

The Silvopastoral Project is being implemented by CATIE in the Atlantic humid lowland of Costa Rica, in order to develop alternatives to the current destructive mode of livestock production. The overall approach is briefly described and two superimposed on-farm experiments are discussed in more detail. The main constraints for on-farm research within the project are analysed: the limited previous knowledge of the area and of the local species, the difficulty of achieving a common understanding about research with collaborating farmers, the need for additional staff supervision and the complexity of the statistical analyses. An attempt is made to draw lessons from the ongoing project regarding how to resolve the apparent contradiction between rigorous scientific requirements and questions of immediate value to extension, the compromises to be achieved between different types of evaluation (statistical, risk, etc.) and the potentials and limitations of farmers' participation in research.     

混沌动力学在森林工程中的应用初探

文中简述了混沌动力学的发展状况，进一步以森林工程学为背景提出了诸如非线性森林工程动力系统等概念及有关研究对象、方法，并通过一个简单的模型算例加以说明，最后对混沌动力学在森林工程中的应用提出了展望。     

Nutrient contribution and maize performance in alley cropping systems

Dry matter yield and potential contribution of N, P and K of some woody perennials as well as performance of maize were assessed in an alley cropping system at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria. Dry matter yield was highest forCassia, followed byGliricidia and theFlemingia. Whereas dry matter yields ofCassia varied significantly at the various pruning times, those ofGliricidia andFlemingia were relatively uniform.Gliricidia contributed the highest amount of N from the cutback (first pruning) and three subsequent prunings. Dry wood yield at cutback was 14.5, 6.8 and 29.7 tonnes/ha forGliricidia, Flemingia andCassia respectively. Coppicing rate was faster inGliricidia thanFlemingia andCassia. Maize height, stover and cob weights were reduced though insignificantly, for the maize rows close to the shrub hedgerows compared to those in the middle of the alleys. For the plots without N application and prunings removed, the maize near the hedgerows showed better performance than those in the middle of the alleys. The results indicate that N supplementation is needed in the alley cropping systems to optimize yield. The amount of N required is higher inFlemingia alleys than forGliricidia andCassia. Root growth of maize was found to be restricted in control plots without hedges; uptake of the major nutrients (N, P and K) was also found to be similarly affected in those plots.