Variance–covariance structure and its influence on variety assessment in regional crop trials

The primary method used to analyze regional crop variety trials is based on the analysis of variance (ANOVA), which requires a homogenous variance–covariance of data. While other models are available, the problem of how the models should be assessed and which model is more suitable for a given trial's data has not been solved. This restricts the applicability of the models. Therefore, a mixed linear model with flexible variance–covariance structures is proposed. Relationships are introduced for various variance–covariance structures of mixed models, and other models for analyzing crop regional trials. Using data from regional corn trials in northeastern and northern China, an assessment was made of the information criterion and likelihood-ratio-test, along with the goodness of fit of variance–covariance structures. This regional trial data facilitated comparison between an ANOVA model and a mixed linear model with an optimal variance–covariance structure. The results showed that the variance–covariance of varietal effects over environmental influences was not homogeneous, as is required in the ANOVA model. Instead, it was found to be heterogeneous in all trials considered. On average, the ratio of significant varietal differences for the same variety was only 86% when comparing the ANOVA model and the optimal mixed linear model. Also, there were obvious differences in the yield ranking of varieties between the two models. The mean standard error of a difference of varietal effects in the optimally-fitted mixed linear model was smaller than that in the ANOVA model.     

新疆冬小麦地方品种高分子量麦谷蛋白亚基的地理分布及其新发现亚基的特性

[目的]和方法]为了揭示新疆小麦地方品种高分子量谷蛋白亚基( HMW - GS)的遗传多样性,对新疆北部地区(北疆)、东部地区(东疆)和南部地区(南疆)小麦地方品种HMW - GS的分布进行了研究.[结果]研究表明:新疆小麦地方品种HMW - GS等位变异的分布与其地理来源具有密切关系,除Glu - B1位点外,Glu -A1和Glu - D1位点等位变异在北部地区、东部地区和南部地区的分布频率存在显著差异.在Glu - A1位点,Glu - A1c编码的亚基出现的频率最高,其次是Glu - A1b编码的2*亚基;但在北部地区,几乎所有品种都含有Glu -A1c编码的亚基,仅有1个品种含有Glu-A1b编码的2*亚基.在Glu - B1位点,新疆大多数小麦地方品种含有Glu -B1b编码的7+8亚基.在Glu - D1位点,新发现的等位基因Glu -D1bp(t)编码的2.6亚基在东疆和南疆出现的频率较高,但在北疆出现的频率最低,分别为91;(东疆),61;(南疆),19;(北疆);等位基因Glu - D1bp(t)在南疆冬小麦地方品种中普遍存在.然而,北疆是以等位基因Glu - D1a编码的2+12亚基为主,其频率为83;.关于Glu - D1bp(t)的起源,推测可能是在南疆地区自然突变产生,然而由于南疆和东疆荒漠化造成的地理阻碍使其向北疆传播的概率较低,同时抑制了该基因向东亚地区的迁移.[结论]基于DNA序列的氨基酸序列比对,发现Glu -D1bp(t)编码的2.6亚基与Glu - D1al编码的2.2*亚基非常相似.     

Climate change impacts,adaptive capacity,and vulnerability of European forest ecosystems

This study compiles and summarizes the existing knowledge about observed and projected impacts of climate change on forests in Europe. Forests will have to adapt not only to changes in mean climate variables but also to increased variability with greater risk of extreme weather events, such as prolonged drought, storms and floods. Sensitivity, potential impacts, adaptive capacity, and vulnerability to climate change are reviewed for European forests. The most important potential impacts of climate change on forest goods and services are summarized for the Boreal, Temperate Oceanic, Temperate Continental, Mediterranean, and mountainous regions. Especially in northern and western Europe the increasing atmospheric CO₂ content and warmer temperatures are expected to result in positive effects on forest growth and wood production, at least in the short–medium term. On the other hand, increasing drought and disturbance risks will cause adverse effects. These negative impacts are very likely to outweigh positive trends in southern and eastern Europe. From west to east, the drought risk increases. In the Mediterranean regions productivity is expected to decline due to strongly increased droughts and fire risks.     

Linkages among agronomic,environmental and weed management characteristics in North American sweet corn

Much of our understanding of weed communities and their interactions with crops comes from studies conducted at, or below, the spatial scale of individual fields. This scale allows for tight control of experimental variables, but systematically ignores the potential for regional-scale environmental variation to affect agronomic operations and thereby influence weed management outcomes. We quantified linkages among agronomic, environmental and weed management characteristics of 174 commercial sweet corn fields throughout the north central United States and evaluated crop and weed responses to these variables using classification and regression tree (CART) analysis. Multi-model selection indicated that characteristics of weed management systems, especially total cost and herbicide rate, were important predictors of weed diversity, interference and fecundity. Adding agronomic variables, such as planting date, or environmental variables, such as latitude, explained additional variation in weed floristic measures. We tested yield predictions of the most parsimonious CART model against a verification data set comprised of over 1500 published observations from 25 experiments conducted in the major North American regions where sweet corn is grown for processing. Yield values fell within the 95% confidence interval of observed data for most branches of the tree, suggesting the experimental and analytical approaches were reasonably robust. Several characteristics favoring sweet corn productivity and weed management sustainability were identified. This work resulted in easily interpretable models, both by scientists and producers, which place crop and weed responses within the context of regional-scale variation in agricultural management and the environment.     

贵州区域经济差异及空间一体化发展对策

比较分析了贵州各行政区域之间、农村区域之间和城乡区域之间经济的绝对和相对差异及其形成原因,并据此提出贵州区域协调发展的空间一体化发展对策。     

基于循环经济的区域REE系统模糊多级综合评价研究

以可持续发展观为指导,以区域资源、环境、经济和谐发展为目标,从循环经济视角出发,建立区域资源、环境、经济(REE)循环复合系统。构建区域REE系统综合评价指标体系,采用层次分析和熵值相结合的主、客观综合赋权法进行权重分析,构建模糊多级综合评价模型,为政府区域发展决策提供依据。     

江苏省产业结构分析

影响区域经济发展的因素很多,如何正确分析我国的区域经济差异,对经济发展具有重要的理论意义和现实意义。本文分析了江苏省产业结构存在差异的原因,提出了不同区域产业结构调整的对策。     

武威市土地利用的地域差异性研究

根据数据的易获取性和现有的技术手段,运用GIS技术及模糊数学方法,对武威市土地利用的地域差异性进行了量化研究。并在此基础上,进一步量化分析了武威市城乡结合部土地利用状况多样性指数、集中化指数及组合类型。结果表明：武威市城乡结合部的土地利用类型表现出明显的多样性和复杂性特征;农业景观虽然在一定程度上仍保持原有农业特征,但已形成为城区服务的城郊型农业。     

浅议江苏省茶叶优势区域发展战略

江苏茶叶生产在全国占有重要地位。改革开放以来,江苏茶叶有了很大发展,但是目前也面临一些困境,如企业规模小,市场混乱,发展速度缓慢等。认为江苏具有生产茶叶的生态适宜性和强大的区域竞争力,适宜发展茶叶产业,对中国的茶叶生产具有重要意义。为了进一步促进江苏茶叶发展,提出了江苏茶叶优势区域发展战略     

灰色关联分析在芸豆区试产量性状上的应用

运用灰色关联度分析法,对2004~2005年芸豆区域试验(4个组)的参试品种8个数量性状与产量进行分析。结果表明,误差变异系数(CEV)低于12%的平均值为8.9%,小于10%,总体上试验误差控制得较好,数据可信;半蔓生(北方组)、直立(北方组)、直立(西南组)的各性状与产量的关联度大小排序基本一致,前3位都为生育日数、荚长、荚粒数,半蔓生(西南组)前三位为株高、荚长、百粒重,说明环境条件对半蔓生型芸豆的产量与各性状关系有一定影响。