用生态农业的观点试论林区草地的开发与利用

通过对地球所面临的资源、环境和人口“三大危机”的概述,表明了生态农业在林草业开发中的重要性。并从生态学和宏观发展战略角度论述了林草业开发利用的价值、途径、前景及对策。     

Landscape characteristics of disturbed shrubsteppe habitats in southwestern Idaho (U.S.A.)

We compared 5 zones in shrubsteppe habitats of southwestern Idaho to determine the effect of differing disturbance combinations on landscapes that once shared historically similar disturbance regimes. The primary consequence of agriculture, wildfires, and extensive fires ignited by the military during training activities was loss of native shrubs from the landscape. Agriculture created large square blocks on the landscape, and the landscape contained fewer small patches and more large shrub patches than non-agricultural areas. In contrast, fires left a more fragmented landscape. Repeated fires did not change the distribution of patch sizes, but decreased the total area of remaining shrublands and increased the distance between remaining shrub patches that provide seed sources. Military training with tracked vehicles was associated with a landscape characterized by small, closely spaced, shrub patches.Our results support the general model hypothesized for conversion of shrublands to annual grasslands by disturbance. Larger shrub patches in our region, historically resistant to fire spread and large-scale fires because of a perennial bunchgrass understory, were more fragmented than small patches. Presence of cheatgrass (Bromus tectorum), an exotic annual, was positively related to landscape patchiness and negatively related to number of shrub cells. Thus, cheatgrass dominance can contribute to further fragmentation and loss of the shrub patch by facilitating spread of subsequent fires, carried by continuous fuels, through the patch. The synergistic processes of fragmentation of shrub patches by disturbance, invasion and subsequent dominance by exotic annuals, and fire are converting shrubsteppe in southwestern Idaho to a new state dominated by exotic annual grasslands and high fire frequencies.     

Does kriging predict weed distributions accurately enough for site‐specific weed control?

Numerous studies have demonstrated the patchy distribution of weeds within fields. The majority of these studies have used discrete sampling, recording weed densities at the intersections of regular grids. In this study, Avena spp. seedlings were recorded on square grids at four sites. The data were then divided into test and real data sets using the whole, two-thirds and one-half of the data to evaluate the consistency of global variogram models and accuracy of ordinary kriging estimates. Kriging provided poor weed density estimates at both very low and high densities, i.e. data were smoothed when compared with true values. Grid sampling took considerable time and, therefore, money to complete, whereas continuous sampling with multispectral imagery (performed at one site) was much quicker and at a finer resolution. It is suggested that sampling systems that collect continuous rather than discrete data are currently more appropriate for site-specific weed management.     

中国的生态农业建设

介绍了生态农业的产生背景，论述了中国生态农业的发展历程及其特点，指出我国的生态农业既不同于西方的生态农业，也不完全是传统农业的回归，它是在中国具有的历史条件和生态经济条件下形成的一种多层次、多结构、多功能的集约经营管理的综合农业生产体系。简介了近20年来在我国生态农业实践中形成的几种成功的生态农业模式，同时对目前生态农业建设中应注意的问题进行了探讨。     

Spatial distribution of weeds in arable crops: are current sampling and analytical methods appropriate?

This paper reviews the literature concerning the spatial distribution of weeds; highlighting the limitations of our current sampling and analytical methodologies, and suggesting how these inadequacies can be addressed. Most research studies have used discrete sampling, i.e. weeds are counted within a quadrat, on a grid basis. Few have mapped weeds at a whole-field scale, either with a resolution appropriate to spraying operations or key ecological processes. Statistical analyses used to describe the data can be divided into two main types, spatially implicit (also at the scale of the sampling unit) or spatially explicit, in which the location of individuals is included in the analyses. Spatially implicit methods can be strongly affected by quadrat size and mean density and are of doubtful benefit. More attention is required to address sampling resolution issues for spatially explicit methods. Our understanding of the formation and dynamics of spatial pattern, as well as predicting the consequences of site-specific management, can be improved with models. Unfortunately, most models consider only newly expanding patches and appear incapable of predicting spatial distributions when an area has been fully invaded. More detailed biological information is required if models are to become more realistic and informative. We also need to ensure that we understand the spatial processes in the context of the whole field environment, to optimize the success of site-specific weed management in the longer term.     

论有机畜牧业之发展

本文论述了有机畜牧业产生的背景,并明确了有机畜牧业的内涵。通过分析国外有机畜牧业发展历程、认证标准,着重探讨我国发展有机畜牧业的优势和必要性,并给出了切实可行的建议和思路。     

开展我国数字草地建设

随着我国数字农业研究与建设的深化,数字草地的研究与建设也迫在眉睫.开展我国数字草地建设不仅是数字农业发展的需要,而且也是草业科技创新之急需.为此,主要从六个方面讨论了我国数字草地建设(1)建设的必要性;(2)发展数字草地的可能性;(3)建设的指导思想、基本原则和目标;(4)数字草地建设体系结构;(5)数字草地建设的内容;(6)数字草地建设的保障措施.     

The use of digital image analysis and real‐time PCR fine‐tunes bioassays for quantification of Cercospora leaf spot disease in sugar beet breeding

Cercospora leaf spot, caused by the fungus Cercospora beticola, is a major fungal sugar beet disease worldwide and the cause of significant yield losses. The disease is most successfully countered by the introduction of genetic tolerance into elite sugar beet hybrids. To this end, breeding programmes require high quality biological assays allowing discrimination of minor differences between plants within a segregating population. This study describes the successful implementation of image analysis software in the bioassays for quantification of necrotic lesions at different stages of C. beticola infection, allowing selection on minor phenotypic differences during the sugar beet breeding process for C. beticola resistance. In addition, a real‐time PCR assay was developed for the quantification of C. beticola pathogen biomass in infected beet canopy. The use of both techniques, even in an early stage of infection, fine‐tunes current bioassays, allowing more accurate and efficient selection of resistant breeding material.     

基于DEM的延河流域水文特征提取与分析

基于DEM数据,依据地表径流漫流模拟算法,使用ArcGIS软件中的水文分析工具,提取与分析延河流域河网特征及相关信息,并与1∶25万地形图数字化水系进行分析比较。结果表明:集水面积阈值是决定河网提取精度的关键参数,阈值越大,提取河网越稀疏,反之则提取河网越密集;随着集水面积阈值的增大,河源数和河网密度、河流的级数、总河长等随之减少,但主河长变化不大;当阈值为5.51 km2时,提取河网与实际较吻合。因此,基于90m分辨率的DEM数据提取延河流域水系和子流域是切实可行的,可以作为数字流域建设与水资源管理的基础数据。     

要实现农业现代化必须发展农业机械化

针对农业机械化对实现农业现代化的重要性,简单论述辽宁省英落镇农机发展的现状,兴农强机的对策,发展农业机械化函待解决的问题。