Land allocation conditioned on El Niño-Southern Oscillation phases in the Pampas of Argentina

The El Niño-Southern Oscillation (ENSO) contributes to the vulnerability of crop production to climate variability in the Pampas region of Argentina. Predictability of regional climate anomalies associated with ENSO may provide opportunities to tailor decisions to expected climate, either to mitigate expected adverse conditions or to take advantage of favorable conditions. Model analysis was used to explore the potential for tailoring land allocation among crops to ENSO phases at the farm scale in two sub-regions of the Pampas. The model identifies as a function of risk preferences and initial wealth the crop mix that maximizes expected utility of wealth at the end of a 1-year decision period based on current costs and prices, and crop yields simulated for each year of historical weather. The model reproduced recent land allocation patterns at the district scale under moderate risk aversion, and predicted increasing diversification with increasing risk aversion. Differences in land allocation among ENSO phases were consistent with known climate response to ENSO, and crop response to water availability. Tailoring land allocation to ENSO phase increased mean net farm income between US$5 and $15 ha⁻¹ year⁻¹ relative to optimizing the crop mixture for all years, depending on location, risk aversion and initial wealth. The relationship between potential value of ENSO information and risk aversion was not monotonic, and differed between locations. Crop mix and information value also varied with crop prices and initial soil moisture. There are potential financial benefits of applying this approach to tailoring decisions to ENSO phases.     

渤海沉积物中微生物铁还原能力及其影响因素探讨

采用恒温厌氧培养实验,以Fe（OH）3为唯一电子受体,通过测定接种不同沉积物提取液后的体系中Fe（Ⅱ）含量变化,研究了渤海沉积物在不同的碳源、温度、厌氧培养时间及pH条件下的铁还原特征。结果表明,从不同水质海区沉积物提取的微生物群落均可以葡萄糖和丙酮酸盐为优势碳源,并迅速还原Fe（Ⅲ）,其利用不同碳源的铁还原能力表现为葡萄糖〉丙酮酸盐〉乳酸盐〉乙酸盐;在不同水质海区之间Fe（Ⅲ）还原程度存在一定差异,Ⅲ类和Ⅳ类水质区域的微生物Fe（Ⅲ）还原能力明显低于Ⅰ类和Ⅱ类水质区域;以葡萄糖和丙酮酸盐作为碳源培养时,在15℃和30℃培养条件下其Fe（Ⅲ）还原反应的活性随着温度的升高而升高,表明微生物在优势碳源下,提高培养温度可促进铁还原反应的效率;淹水时间延长可改变微生物群落结构,促进利用葡萄糖和丙酮酸盐的微生物恢复增长,使Fe（Ⅲ）还原能力增强;微生物群落在pH中性体系条件下Fe（Ⅲ）还原能力最强,随着体系pH值由8.0升高到11.0或pH由6.0降低到3.0,体系中Fe（Ⅲ）还原能力均逐渐降低。     

农村基层档案的利用价值及服务模式探讨

农村基层档案是地方文献的重要组成部分,它以地方文献服务模式的特点,服务于中国农村研究的各个领域,对中国农村政治、农村经济、农村文化、农村历史的研究有着重要的学术价值。     

农业资源综合利用效率的评价方法及案例分析

基于对农业资源高效利用的概念和特点的认识并考虑资料的来源和计算的可行性,建立了农业资源综合利用效率的评价指标体系,提出了农业资源综合利用效率的评价方法,以河北省奕城县为例进行分析计算,得出了初步结论。     

A heuristic optimization method for forest planning and decision making

The presented planning method searches for an optimal combination of treatment schedules for forest compartments by maximizing, in an iterative manner, an additive utility function. The variables of the utility function can be selected from parameters that are associated to the whole forest area, such as; amount of removal, costs, income, or volume of the growing stock. Partial utility functions are developed for each objective variable the total utility being a weighted sum of the partial utilities. The weights of the objectives and the partial utility functions are estimated using the Analytic Hierarchy Process. Development and estimation of the utility function makes decision analysis an integral part of the planning process. The method was used with a non‐industrial private forest, but the approach is also applicable to many other forest planning situations.     

小型通用汽油机排放的研究

以168F汽油机为样机,通过改变点火提前角和混合气浓度供给实测了样机的功率、油耗和排放数值。通过发动机示功图采集和放热规律计算,研究了点火提前角和混合气浓度对样机工作过程的影响,探讨了与样机匹配的点火提前角和混合气浓度的最佳值。通过上述试验研究和理论分析,在不使用尾气催化转化器的情况下,使得样机达到EPA第二阶段排放限值,并且具有达到EPA第三阶段排放限值的潜力。     

黄河三角洲湿地水生维管植物资源及其利用研究

黄河三角洲湿地水生维管植物种类丰富,据调查统计,共有水生维管植物64种,隶属25科40属,依其形态特征和生活习性划分为挺水植物、沉水植物、浮叶植物、漂浮植物4个生活型。同时,对水生维管植物的用途进行了综述并就其利用、保护提出了建议。     

经济代理人的最优损失控制

根据经济代理人对风险的厌恶程度高低将影响收益效用的事实,通过对经济代理人的风险厌恶系数引进阈值,使风险厌恶系数在不同取值区间对应不同的效用函数,对经济代理人具有常值绝对风险厌恶的效用函数,损失服从泊松分布、且保险市场被垄断的承保人控制的最优防损活动进行了研究.研究表明,风险厌恶系数、损失的大小以及防损效率将影响最优防损水平.     

浅论农业科研投入的开源与节流

对河南省农业科研投入现状、特点做了简要分析,表明现阶段河南省农业科研投资强度偏低,结构不甚协调。在此基础上,对增加河南省农业科研投入,改善农业科研投资结构提出了若干政策建议。     

邵武将石省级自然保护区兰科植物多样性及保护利用

初步统计,邵武将石省级自然保护区共有兰科植物34属64种(铁皮石斛及落叶兰为福建新记录种)。区内兰科植物生活类型多样,区系成分比较复杂,各种地理成分相互交错,渗透现象明显,以热带成分22属(含38种、占总属数64.7%)占优势,温带成分10属(含19种、占总属数29.4%)影响较大。调查发现,区内兰科植物花期重叠与交替现象明显,并存在种下异变。针对资源濒临绝迹现状,提出保护利用的对策。