Residue management of a planted fallow on an acid soil in Cameroon: crop yields and soil organic matter fractions

A fallow management trial was initiated in March 1990 in Yaounde, Cameroon, with the objective of identifying an efficient method of managing residue derived from a planted fallow of Cajanus cajan. Ten months after establishment, the shrubs were slashed and residues were treated in one of the following ways: burnt, incorporated in the soil, mulched on soil surface or removed. Following that, maize and groundnut were planted. Soil organic matter was fractionated after the residue treatments, and elementary partial budgeting was conducted. After three cycles of fallow and cropping seasons, maize yield was similar, about 3 t ha^-1, in all plots except in the residue-removed plots, where it was 1.4 t ha^-1. Yield trend of groundnut was also similar. The residue management method did not affect either the nature of fractions or the total content of soil organic matter. The highest net return, US$5945 ha^-1 year^-1, was obtained from the residue incorporated treatment, whereas the highest return to labour, US$11 per manday^-1 was associated with burning of residues. In areas such as the forest zone of Cameroon where labour is a major constraint and climatic conditions allow vigorous vegetation growth, burning appears to be the best method of residues management, at least in the short run. This revised version was published online in June 2006 with corrections to the Cover Date.     

毛竹主要营林措施技术经济效果分析

本文分析了毛竹主要营林措施松土、施肥和留养母竹及其综合技术的经济效果,分析表明,不同松土深度亩产值间具有极显著差异,松土以25cm为好,这时反应弹性大,纯收入高。施氮肥和有机肥可极显著增产产,尿素以每亩施20kg为佳;有机肥增产作用大小顺序是饼肥＞猪栏肥＞干稻草＞青草。母竹以留养四度为好,由于△NPV均大于零说明松土25cm、施尿素20kg／亩、留四度母竹及其综合技术都是可行的,可根据当地人、财、物资 况选用。从△NPVR值来看,投资效益以每亩施20kg尿素最好然后依次是松土25cm、综合技术和留四度母竹。     

成武县农田林网适宜采伐龄的确定

对影响成武县农田林网采伐龄的因素做了全面系统的分析,认为除了林网本身的因素以外,防护成熟龄、气象条件、林网规格、更新方式、林粮间作和林带结构等,都是影响林网采伐龄的因素。因此,确定采伐龄应综合考虑各方面的影响,实现最佳综合效益。另外,根据一具体实例,对其采伐龄进行了研究。认为综合净现值既能体现林网本身的直接效益,又能反映林网护农增产效益,是比较合理的依据。     

Defining competition vectors in a temperate alley cropping system in the midwestern USA: 4. The economic return of ecological knowledge

We tested the economic value of ecological knowledge in a midwestern USA alley-cropping system where row crops are planted in alleys between fine hardwood trees grown for veneer. Economic models were constructed to compare among agroforestry designs as well as to compare agroforestry with traditional forest plantation culture and row crop monoculture and rotational management. The general modeling approach was to quantify production inputs and outputs, estimate costs and revenues, simulate tree growth and crop productivity in agroforestry configurations, and estimate discounted cash flows. We incorporated scenarios that controlled both above- and below-ground competition through appropriate management as found in our previous research. This research showed the importance of below-ground competition in determining crop yields and the period of time that crop income could be expected from the agroforestry interplanting. Net present values and internal rates of return showed that agroforestry systems were generally more favorable investments than traditional agriculture and forestry. More importantly, the use of simple management techniques targeted at reducing below-ground competition allowed longer cultivation of row crops, greatly increasing returns to the landowner. Thus, the economic benefit of understanding the ecological interactions within agroforestry plantings dictates that accurate assessment of agroforestry alternatives will require the modeling of agroforestry as an integrated, interactive system.This revised version was published online in November 2005 with corrections to the Cover Date.     

应用抚育间伐资料确定经济成熟龄的初步研究

为了克服森林经济成熟龄研究中固定标准地数量少,设置年限短、资料相对贫乏和基础数据可靠性较低等缺点,本文采用来源丰富、数据可靠的间伐(或主伐)作业标准地调查表为原材料,以动态分析评价经济活动的净现值(NPV)为指标,从径级分布这个最基本的数据算起,对隆化县茅荆坝林场阴坡厚土人工油松林进行了分析,力图精确,动态地反映林地的径级分布、材种(类)出材量、价格等随年龄的变化,以确定适宜的经济成熟龄。结果表明,茅荆坝阴坡厚土人工油松林的净现值最大的年龄是27a,即为其经济成熟龄。     

杉木种子园不同营建方式成本分析

本文以现金流、折现值、净现值为指标,引用动态经济评价方法,对湖南省会同县不同建园方式的杉木种子园前期成本进行对比分析。结果表明：新建园先在苗圃培育2年生容器砧木,第3年圃地嫁接,第4年移植至种子园,这种方式相对传统的在园区培育3年生砧木,第4年园区嫁接无性系的建园方式,30 hm2规模前4年投入少37.68万元,节约23.83%,净现值增加40.76万元,增加27.44%,建园方式的创新经济效益显著。     

A model to calculate ex ante the threshold value of interaction effects necessary for proposed intercropping projects to be feasible to the landowner and desirable to society

This article describes an approach to evaluate the difference in net present valued economic returns that would be expected from temperate intercropping as compared to annual cropping or tree farming alone. This tool can be used by landowners to provide a threshold level of the value of interaction effects required for a proposed intercropping project to break even, based on current data. The landowner would then need to consider, using information from other sources, whether the threshold is realistic for given site conditions. The threshold value is useful to agricultural policy-makers to consider economic instruments that would induce landowners to adopt intercropping, if it should be considered socially beneficial to do so. The approach measures the financial gap that exists between intercropping and annual cropping alone and compares this gap to the beneficial interaction effects that are associated with intercropping. The approach is demonstrated using experimental results from an on-going intercropping study at the University of Guelph, Guelph, Canada. A base model scenario using black walnut trees with annual crops is set up with a 5% discount rate, 96 trees per hectare, and sawlog prices for black walnut of $1066 per 1000 bdft as a base case. The base model predicts that black walnut and corn intercropping returns $555 per hectare less than the annual crops alone, over the entire rotation of trees. This amounts to about $42 per hectare per year in annual terms, at a 6% rate of discount. This is the threshold that would need to accounted for by the net present value (NPV) of on-farm interaction effects. This estimate depends on the specific assumptions made and the experimental situation, and should not be interpreted as reflecting returns possible in other circumstances. This revised version was published online in June 2006 with corrections to the Cover Date.     

Determining the Ecological Compensation Standard Based on Forest Multifunction Evaluation and Financial Net Present Value Analysis: A Case Study in Southwestern Guangxi,China

ABSTRACT

There is growing concern that public benefits from forests are underprovided in current forest management regimes and need to be increased through policy and economic measures that promote conservation. Ecological compensation is a type of institutional arrangement for the sustainable use of ecosystem services achieved by adjusting the distribution of costs and benefits among different stakeholders using economic measures. However, how to accurately and reasonably determine the compensation standard for ecological services has not been guided by scientific methods and theories. This study provides an estimation of the compensation standard for forest ecological services based on the forest multifunction evaluation and financial net present value analysis, and a case study was performed in Southwest China. The results showed that most forest types brought some economic loss to the managers but contributed great ecological benefits to the public when they were managed as ecological forests. It is crucial to incentivize forest managers to participate in voluntary conservation programs through ecological compensation. The results of this analysis can potentially guide sustainable forest management by both accurate quantification of the value of forest ecosystem services and an improved understanding of the costs of voluntary forest conservation schemes currently in use in many countries.     

税费变化对马尾松资产经营决策影响分析

以马尾松中径材经营类型的各生长指标为基础,结合所收集的延平区有关技术经济指标以及林业不同时期的税费情况,利用不同方法测算不同税费水平下马尾松林地的资产价值,进而定量分析其影响趋势,从而为马尾松资产经营决策提供参考,为林业税费的进一步改革提供参考。     

税费变化对马尾松资产经营决策的影响分析——以福建南平市为例

以马尾松中径材经营类型的各生长指标为基础,结合所收集的福建南平市有关技术经济指标以及林业不同时期的税费情况,利用不同方法测算不同税费水平下马尾松经营的净现值与内部收益率,进而定量分析其影响趋势,为马尾松资产经营决策及林业税费的进一步改革提供参考。     

广西大青山米老排人工林经济效益分析

米老排(Mytilaria laosensis Lecomte)又名壳菜果、三角枫,为金缕梅科常绿乔木树种,天然分布于我国广东、广西和云南省区以及越南和老挝等地,具有速生、干形通直圆满、材质优良,兼具改良土壤、保持水土等优点,是建筑、家具、造纸和人造板的优质原料.鉴于该树种的优良特性及广泛用途,已有学者对其进行了育种、栽培、木材材性及利用开发等基础应用研究[1-6];但有关该树种的投资收益状况未见报道,这在一定程度上影响了米老排树种的发展与推广.     

杉木人工林碳汇木材复合经济收益分析及最优轮伐期确定——基于时间序列预测模型

[目的] 探讨不同条件下杉木人工林碳汇木材复合经济收益及最优轮伐期的变化,为杉木经营者在碳汇交易背景下选择最优森林经营决策提供依据。[方法] 以闽西北杉木人工林为研究对象,基于实地调查数据,利用时间序列预测模型（ARIMA）对杉木人工林蓄积量和碳储量进行拟合预测,并以此为基础数据,结合相关经济指标,采用年均净现值法（ANPV）和林地期望价法（LEV）分别计算杉木人工林经济收益和最优轮伐期;同时比较分析最优轮伐期和最大经济收益对立地质量、碳价格、利率3个不确定因素变化的响应。[结果] 1）ARIMA模型对杉木人工林蓄积量和碳储量的拟合结果精度较高（预测模型中最低R²为88.460%）,以此获取了有效的林分生长预测数据;2）鉴于木材价格远高于碳价格的现状（取利率5%、理论碳价格173元·t^-1的情况）,增加碳汇经营目标并未改变以经济成熟为标准的最优轮伐期,但碳汇木材复合经济收益明显提高,对于不同立地质量的林分,其最大经济收益增加6.55%~10.12%（ANPV）和6.60%~10.72%（LEV）;3）地位指数增加、碳价格提升及利率提高,都会导致最优轮伐期不同程度地提前,但影响效果存在差异。立地质量越好,碳价格越高,复合收益就越多,当碳价格达到600元·t^-1时（取利率5%）,不同立地质量的林分经济收益增加25.01%~35.09%（ANPV）和22.90%~37.19%（LEV）;但高利率会导致经济收益明显降低,以立地指数14~16 m为例,当碳价格为123元·t^-1时,在4%利率水平下林地复合经济收益几乎是7%利率水平下的3倍。[结论] 1）基于现实林分调查数据的时间序列预测模型（ARIMA）对林分生长进行预测值得尝试和推广;2）在现有杉木经营环境下,即使增加碳汇经营目标,经营者在不改变采伐期的情况下也能获取最大复合经济收益,有利于经营者增加收入,增强其从事杉木经营的积极性;3）立地质量越好,碳汇木材复合经济收益越高,因此,选择立地条件较好的林地进行杉木造林,能提高经营者的经济收入;4）碳汇木材复合经营目标下,碳价格提高能有效提升杉木经营者的投资效益;5）利率的增加,碳汇木材复合经济收益明显降低,因此高利率不利于杉木人工林的经营。由此可见,碳汇木材复合经营对增加杉木经营者经济收益和发挥人工林碳汇潜力都具有重大的现实意义。     

Napier grass strips and livestock: a bioeconomic analysis

Napier grass strips are gaining some acceptance in Southeast Asia as a vegetative means of soil erosion control, due to the relative ease of establishment and management. In addition, the napier grass strips aid productivity of agroforestry systems by providing mulch or by being fed to livestock. In this paper, a bioeconomic comparison of different ways of utilising the napier grass cuttings is undertaken. The three uses examined for the cuttings were: as mulch in the alley areas, sold as fodder, and fed to animals with manure applied back to the system. The analysis linked the soils-oriented SCUAF model with economic and animal component models. SCUAF was parameterized using field data based on farmer interviews and field visits. Farmer interviews and field visits were conducted at Claveria, Misamis Oriental to gather additional data regarding costs and returns associated with animal production, and also to obtain the farm gate price of napier. Predicted biophysical results produced by the SCUAF model showed that application of napier grass cuttings, back into the system, directly as mulch or indirectly as animal manure resulted in higher maize and napier yields, lower soil erosion rates, and less of a reduction in soil mineral nitrogen and soil labile carbon levels. The comparison was made with the case where napier was sold off-farm as fodder. Cost-benefit analysis showed that higher economic returns were gained when napier grass cuttings were fed to animals, rather than applied directly as mulch. This economic benefit was attributed to the draught and transport services rendered by the animal and to a change in the value of the animals. This analysis highlights the value of utilizing animals within a napier grass strip system for control of erosion.This revised version was published online in November 2005 with corrections to the Cover Date.     

A study of alley-cropping data from Northern Brazil. I. Distributional properties

Measurements from trees and plants of a BrazilianInga/maize/beans alleycrop experiment were assessed for their distributional properties for three years of the study. Results for the tree data were similar to those found in an earlier study. Results for the crop data demonstrated similarities between the distributions for alleycrops and solecrops, nonnormality shown by positive skewness and peaked distributions. Changes in the distributional shapes were demonstrated from year to year as soil nutrient depletion increased and as climatic variables fluctuated. Variation across the rows in the alley was often of a similar size to variation from plant to plant within the rows. Initial recommendations for analysis of such data are given on the basis of these results.     

The spatial and temporal effects of paulownia intercropping: The case of northern China

We present a financial analysis and further statistical tests of the spatial and temporal effects of intercropped paulownia (Paulownia elongata) trees on crop yields. The results provide evidence that growing paulownia trees in farm fields can either increase or decrease crop production, depending on the manipulation of the tree density and rotation length. A 60–100% reduction of crop yields can result from a higher tree density and/or a later stage of the rotation, but the pattern of reduction is different for the first (wheat) and second crops (corn, bean or cotton). However, the reduction in crop yield is accompanied by gains of timber, fuel, fodder, and other goods and services. Thus, although the accumulated net returns from crops decline as tree density increases, the combined net returns of crops and trees are generally higher than those of the control, ranging from 50% to 100%. This revised version was published online in June 2006 with corrections to the Cover Date.