苏北滨海盐土区杉木生态适应性及栽培技术的研究     

王为耘  丁神奇 《江苏林业科技》1996,23(3):32-35

调查研究结果表明，盐城市滨海盐土区与杉木中心产区的气候因子比较接近，基本适宜杉木的生长，杉木造林选择地下一在１．５ｍ以下，排水良好的采伐更新迹地并采用 栽植法效果较好。新造幼林套种作物以棉花最好。  相似文献   

家畜繁殖生物技术研究现状及趋势     

张继慈 《西北农业学报》1992,1(2):75-79

牛胚胎移植技术已趋于成熟。我国新疆牧科院用一步细管法移植牛冻胚受胎率达41%;牛和羊鲜胚四分胚移植也产下1头犊牛和6只羔羊。家畜体外受精,因卵子体外成熟和受精卵体外培养尚不过关,目前仍停留在实验室阶段。胚胎性别鉴定,1990年Koopman发现单拷贝基因,该基因是Y染色体的性决定区,命名为SRY,可利用PCR技术制成雄性特异DNA探针盒,进行马、牛、羊、猪早期胚胎性别鉴定。北京农学院等单位用PCR扩增牛SRY序列进行奶牛胚胎性别鉴定准确率达100%。英、日、法等国已获得牛胚胎细胞核移植后代;我国也获得1只核移植兔。北农大和新疆牧科院合作以绵羊精子为载体导入牛生长激素基因rMTbGH DNA成功,外源基因整合率为3%。  相似文献   

农用地因素法与样地法分等对比研究——以重庆市丰都县为例     

刘燕红陈务魁  胡渝清王玥 《四川畜牧兽医学院学报》2006,4(1):8-11

对现行《农用地分等规程》中因素法和样地法进行探讨，寻求农用地分等的最佳方法。文献资料法、比较分析法。《规程》中因素法分等使得研究区单元分值出现拐点，划分等别部分与实际不符；样地法分等结果则不存在这一问题。在农用地分等中，在县域内种植制度为一年两熟和一年一熟的地区采用样地法分等更合理。  相似文献   

影响绵羊冻胚移植妊娠率的因素分析     

余文莉  李树静  付静涛  李培源  白音 《中国畜牧杂志》2006,42(7):12-14

本研究对胚胎质量、胚胎移植数量、胚胎发育阶段、冷冻方法、移植方法及饲养管理水平等因素对移植产羔率的影响进行研究,以提高绵羊胚胎移植效率。结果表明:采用1.5mol/L乙二醇做冷冻保护剂对胚胎进行常规冷冻,冻前A级胚胎冷冻/解冻后可用胚率、存活率、降级率均高于B级,差异极显著(P<0.01)。移植1枚冷冻解冻后A级、B级或2枚(A+B)胚胎的受体移植产羔率分别为44.48%、46.84%和44.81%。经χ2检验分析,三者之间无显著差异(P>0.05)。移植双胚的受体双羔率为22(%53/241),以胚胎为单位计算,产羔率仅为33.40%。A级囊胚和桑椹胚的产羔率之间无显著差异(P>0.05)。1.5 mol/L乙二醇常规冷冻保存的体内胚胎移植产羔率高于EFS40玻璃化冷冻保存,但经统计学分析,二者无显著差异(P>0.05)。子宫手术移植和腹腔内窥镜法子宫移植之间产羔率不具统计学差异(P>0.05)。在牧场条件下大规模移植的平均产羔率为43.95%,范围在20%￣70%之间,受体饲养管理水平对绵羊移植产羔率有较大影响。  相似文献   

实广义正定矩阵的若干性质     

袁德正 《内蒙古农业大学学报(自然科学版)》1990,(2)

矩阵∈AR~(n×n)称为实广义正定矩阵,如果对任意非零向量 X∈R~n,有XTAX>0成立。本文讨论了矩阵的kronecker积。Hadamard积和矩阵乘积的正定性,给出相应一些性质。  相似文献   

参与式方法在退耕还林中的应用     

郑智礼 《林业与社会》2005,13(4):37-39

本文分析了退耕还林程序和山西省PAAF项目的经验.提出在制订退耕还林县级年度方案、具体实施过程和检查验收等阶段应用半结构访谈、村民大会、实施管理条例以及实施小组和监测小组等参与式工具.  相似文献   

Landscape-ecological mapping of the Netherlands   总被引：1，自引：0，他引：1  

Kees J. Canters  Cees P. den Herder  Aart A. de Veer  Paul W. M. Veelenturf  Rein W. de Waal 《Landscape Ecology》1991,5(3):145-162

The Landscape-ecological Mapping of the Netherlands project (LMN project) started in 1983 with the aim of establishing a landscape-ecological database for use in developing and evaluating national land-use plans. The project, working with grid cells of 1 km², has four working objectives: a) development of mapping potential for basic landscape-ecological data, b) assessment of susceptibility to interventions, c) evaluation of significance for nature conservation and d) production of vulnerability maps, as a combination of susceptibility and significance. In addition to information on soil, groundwater, ecotopes, flora and fauna, the database also incorporates information on physiographical features and entire landscapes. The resulting database is a geographic information system (GIS). This article describes the second phase of the project (1985–1989), covering the Randstad area, and focusses on the methods and the applications potential of the database.  相似文献   

供水工程影响下中国北方地区耕地后备资源开发潜力     

李溦  何国华  赵勇  姚圆  何凡  李海红  王浩 《农业工程学报》2024,40(5):264-274

灌溉水源是北方地区耕地后备资源能否有效开发的关键。当前,中国正在推动国家水网工程规划建设,为北方地区耕地后备资源开发提供了新的机遇。在以往研究基础上,该研究考虑北方地区已建、在建及规划的供水工程,基于自然适宜、利用高效、发展稳定三方面评价准则,结合三维魔方空间分类方法,开展了雨养情景和供水灌溉情景下耕地后备资源开发潜力分析。结果表明：雨养农业情景下,北方地区勉强适宜（Ⅱ级）、中度（Ⅲ级）和高度（Ⅳ级）适宜的耕地后备资源面积分别为2.9万、1.0万和0.6万km²。灌溉农业情景下,耕地后备资源面积明显增加,勉强适宜（Ⅱ级）、中度（Ⅲ级）和高度（Ⅳ级）适宜的耕地后备资源面积将分别达到5.4万、7.6万和6.5万km²,主要集中于新疆、内蒙古和甘肃3省（自治区）。该研究结果可为中国耕地后备资源开发利用及国家水网工程效益发挥提供参考。  相似文献   

An investigation of uncertainty in field habitat mapping and the implications for detecting land cover change     

Andrew Cherrill  Colin McClean 《Landscape Ecology》1995,10(1):5-21

Land cover data for landscape ecological studies are frequently obtained by field survey. In the United Kingdom, temporally separated field surveys have been used to identify the locations and magnitudes of recent changes in land cover. However, such map data contain errors which may seriously hinder the identification of land cover change and the extent and locations of rare landscape features. This paper investigates the extent of the differences between two sets of maps derived from field surveys within the Northumberland National Park in 1991 and 1992. The method used in each survey was the Phase 1 approach of the Nature Conservancy Council of Great Britain. Differences between maps were greatest for the land cover types with the smallest areas. Overall spatial correspondence between maps was found to be only 44.4%. A maximum of 14.4% of the total area surveyed was found to have undergone genuine land cover change. The remaining discrepancies, equivalent to 41.2% of the total survey area, were attributed primarily to differences of land cover interpretation between surveyors (classification error). Differences in boundary locations (positional error) were also noted, but were found to be a relatively minor source of error. The implications for the detection of land cover change and habitat mapping are discussed.  相似文献   

新疆退牧还草工程建设与管理的探讨     

张江玲杨刚  王旭明 《四川草原》2005,(9):41-42

草地是发展畜牧业的重要基础,退牧还草工程是恢复、更新天然草地和保护生态环境的重要手段。本文就新疆实施退牧还草工程中所出现的一些问题进行了探讨。  相似文献