我国农田土壤污染的环境成本分析

从粮食减产及质量下降的直接损失和生物多样性降低的间接损失2个方面,计量了我国农田土壤污染的环境成本。结果表明,1990~2005年我国粮食生产造成的农田土壤污染的环境成本约为208.54亿元/a,其中粮食减产及质量下降的直接损失为21.61亿元/a,农田生物多样性降低的间接损失为186.93亿元/a。     

Kalmia removal increases nutrient supply and growth of black spruce seedlings: An effect fertilizer cannot emulate

In Canada's eastern boreal forest, the stagnant growth of black spruce (Picea mariana (Mill.) BSP) seedlings is often observed in the presence of ericaceous shrubs such as Kalmia angustifolia L. Many mechanisms, including allelopathic interference, reduced soil N mineralization, soil enzymes inhibition, and direct resource competition have been proposed to explain poor spruce growth in the presence of Kalmia. However, the relative importance of direct competition versus indirect interference remains unclear. Our objective was thus to adequately isolate the “Kalmia effect” from other growth-limiting factors and to determine if removal of Kalmia also resulted in fundamental changes in the biochemical properties of the forest floor. By sampling plots established in 2000, we evaluated how Kalmia eradication and spot fertilization influenced soil nutrient availability, N mineralization rates, microbial basal respiration and biomass, as well as planted black spruce seedling growth, dimensions, and foliar nutrient concentrations 6 years later. We measured higher extractable-P, mineralizable-N, seedling dimensions and growth rates, as well as lower extractable-K, total-K, basal respiration and microbial biomass, in plots without Kalmia than in those where Kalmia had been maintained from 2000 to 2006. Our results thus confirmed that Kalmia eradication over 6 years not only improved the growth and nutrition of black spruce seedlings, but also resulted in fundamental changes in the biochemical properties of the forest floor. We demonstrated that along with direct competition for resources, Kalmia interferes indirectly with black spruce by modifying nutrient cycling and energy fluxes in soil. Higher indices of available C in plots with Kalmia corroborates that Kalmia tannins or rhizodeposition may reduce N mineralization by stimulating microbial immobilization, a relation that however needs to be confirmed with longer term laboratory incubations. Our results indicated that although it had a positive influence on seedling growth, the fertilization effect was confined to the first few years following treatment application, and failed to influence soil processes as did Kalmia eradication. Further monitoring will indicate if the increased litterfall in fertilized plots will eventually initiate a second wave of fertilizer-induced changes to soil processes, as observed in other ecosystems.     

Real-time controlled direct injection system for precision farming

Real-time controlled pesticide application requires a fast reacting system, enabling continuous variation of pesticide type and concentration based on a control signal. Direct injection systems meet the requirements for such application; however there are significant differences in the response time and quality of single system designs. This article discusses the complex of problems in direct injection systems in connexion with real-time control and proposes optimisations of system parts in order to reduce the response time and improve the quality of the process. The system response time was reduced to 160 ms for 1% output concentration by optimization of the control process, injection assembly and mixing chamber design.     

紫花苜蓿组织离体培养的形态建成及其调控

本文对紫花苜蓿 (Medicago Sativa L .)组织离体培养并附加植物生长调节物质进行调控。研究表明 :紫花苜蓿愈伤组织的形成可分为 3个阶段 :启动期、分裂期及形成期。同时阐述紫花苜蓿愈伤组织的分化及其调控过程以及植物器官的发生 (苗的发生和根的发生 )。     

水分胁迫对芒果成花效应及内源激素变化的影响

以３ａ生盆栽红芒６号为试材,研究水分胁迫对芒果成花的效应。发现水分胁迫能改变芒果植株梢尖内源激素的水平及激素间的平衡,使 ＧＡ减少,ＡＢＡ和 ＣＴＫ增加,ＣＴＫ／ＧＡ及ＡＢＡ／ＧＡ的比率提高,抑制营养生长,促进开花,成花率高达 ７５％;而对照（灌水）植株营养生长旺盛,萌发新梢,抽梢率３７．５％,成花率仅６．２５％。      

Survival and Early Development of Lodgepole Pine

The effect of site fertility, spacing and mode of regeneration on the survival and stand development of lodgepole pine, Scots pine and Norway spruce was studied in a series of experiments comprising 22 study areas in Finland. After 13-14 yrs, lodgepole pine had a mean survival of 68% in planted and 61% in seeded plots, while Norway spruce had the highest (92%) and Scots pine the second highest survival (82%). The survival of planted lodgepole pine was better the wider the spacing. Best survival was achieved on subdry and dry sites, both with planting and with direct seeding. Dominant height was not affected by spacing, but both basal area and volume at the age of 13-14 yrs were significantly higher the denser the spacing. The average difference in the value of the estimated site index H ⁵⁰ was slightly under 3 m for the superiority of lodgepole compared with Scots pine. Seeding resulted in site indices almost as high as those of lodgepole planting.     

Non-industrial Private Forest Owners' Risk Preferences

A set of hypotheses was formulated on the basis of available knowledge about non-industrial private forest (NIPF) owners' risk preferences. The empirical material used for testing the hypotheses was gathered in telephone interviews with 130 randomly selected NIPF owners. The results confirm that direct economic risks such as price and cost changes are seen by this group as much more important than indirect economic risks such as biological damage. The forest owners regarded forest holdings as a safer investment than stocks or bank savings. The results on risk attitudes were ambiguous. However, when larger amounts of money were at stake, the forest owners could be considered risk averters and a decrease in absolute and relative risk aversion could be confirmed.     

太阳辐射直接透射率的推算

利用来自全国66个日射站的太阳辐射及679个常规气象站的日照资料,在数据集群的基础上,建立了直接透射率的不同（各站各月模式、各月模式、各站模式、综合模式）估算模式,研究直接透射率的推算方法。经过对各种模式计算结果的误差指标的综合评估分析,最终确认各月模式为最优模式。文章选取各月模式,在GIS支持下利用Kriging内插法,得到1km×1km的全国月直接透射率空间分布图,并分析了月直接透射率的空间分布及主要影响因素。     

叶籽银杏的发生及其个体与系统发育研究述评

叶籽银杏是银杏资源中一个极为奇特的种质,具有重要的观赏和学术价值.目前,中国和日本已报道的叶籽银杏共有47株,树龄36～1 200年不等,叶生种子发生率为5%～25%.银杏的可育短枝整体上相当于松柏类的一个雌球果(大孢子叶球).叶籽银杏可能与种子蕨和苏铁类等有较近的亲缘关系.叶籽银杏的发生机制有返祖学说、衰老学说、环境诱变学说等,综合分析后提出嵌合体学说,其发生可能与同源异型盒基因的表达有关.本文对目前叶籽银杏的分类地位的多种观点进行评述,系统概述叶籽银杏的分布状况,形态解剖学、细胞生物学、分子生物学研究现状,分析银杏雌性生殖器官的形态学本质,及叶籽银杏可能的亲缘关系,对叶籽银杏可能的发生机制进行了探讨,并提出叶籽银杏研究中存在的几个主要问题及今后研究的建议.     

对燕麦穗重的直接及间接选择

燕麦(A.sativa L)穗重是重要的籽产构成因素,但由于遗传力低,对其选择的可靠性较差.本试验以F_3代杂种为材料,依收获指数十株高的指数对穗重进行了间接选择,并和其直接选择的效果进行了比较.结果表明,收获指数和株高的遗传力均较低,同时它们同穗重的遗传相关也不够高,间接选择的效果不明显.另外,收获指数同株高呈高度负遗传相关(γ_g=-0.6392),把收获指数高和植株高两个特性结合在一起也是困难的.