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91.
干旱半干旱区土壤风蚀评价方法 总被引:16,自引:0,他引:16
李玉宝 《干旱区资源与环境》2000,14(2):48-52
土壤风蚀是导致干旱半干旱地区土地退化和区域环境恶化的最重要的原因之一。本文从区域土壤风蚀评价与监测需要出发 ,提出了一套土壤风蚀评价的指标体系和制图方法 ,其特点是 :(1 )充分利用 3 S技术 ;(2 )把耕地、沙丘地同其它土地类型区分开来 ,使用不同的指标体系 ;(3 )分别提取每一图斑的各指标因子 ,并建立相应的数据库 ;(4)强调限制性因子。 相似文献
92.
欠发达地区的农业发展受到地理区位、自然资源禀赋、产业基础条件、劳动力素质、制度创新、公共品供应等问题的强力约束而举步维艰。随着欠发达地区新农村建设的启动和不断推进,如何利用这一过程中产生的各种条件解决问题化解矛盾,促进农牧业经济获得快速高效发展,是个值得深究的问题。本文从以上几个方面入手,提出针对性的几点建议。 相似文献
93.
当前,全国上下正在全力推进乡村振兴战略的实施。乡村振兴,产业兴旺是重点。如何实现乡村产业振兴、产业兴旺,这是值得研究的紧迫而现实的重要问题。本文首先从乡村产业振兴在乡村振兴战略中的地位与作用入手分析,对新中国成立70年来中国乡村产业发展的历程进行了简要回顾,并将其划分为4个发展阶段:第一阶段:1949—1977年,传统产业缓慢发展;第二阶段:1978—2000年,乡镇企业异军突起;第三阶段:2001—2011年,新型产业不断涌现;第四阶段:2012年至今,乡村产业绿色"转型"。同时也指出了当前中国乡村产业存在的突出问题,即:产业门类少、生产规模小、产业层次浅、产业链条短、生产效率低、特色产业弱、品牌产业缺、产业环境差、产品质量低和缺乏竞争力。最后,针对上述存在的问题,提出了实施乡村振兴战略、实现乡村产业振兴要遵循的6大原则和10项具体措施,以期为推动实施乡村振兴战略做出积极贡献。 相似文献
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95.
YANG Hui CAO Jianhua ZHANG Liankai HOU Yanlin MAO Lifeng Graduate University of Chinese Academy of Sciences Beijing China Institute of Karst Geology of CAGS Guilin Guangxi China Environmental Management College of China Qinhuangdao Hebei China International Culture College of Capital Normal University Beijing China 《东北农业大学学报(英文版)》2011,18(1):39-45
The three-pool and first-order model separates the mineralizable organic carbon into active,slow,and passive carbon pools.This paper used the model and decomposition curves of the soil organic carbon to fit the active pool and its decomposition rate,slow pool and its decomposition rate.The results showed that the size of the active pool from different profiles accounted for 2.09%-3.08% of the total soil organic carbon and the mean residue time was 3.57-17.21 days.And the size of the slow pool accounted for ... 相似文献
96.
大兴安岭火烧迹地植被恢复中植物多样性与生物量分配格局 总被引:1,自引:0,他引:1
为了探讨火烧迹地植被恢复中植物多样性和生物量及二者关系,采用时空互代法,以大兴安岭重度火烧迹地不同恢复年限落叶松人工林为研究对象,以天然白桦林作为对照样地,对乔木层、灌木层、草本层和群落物种多样性指数及生物量进行了研究。结果表明:1)植被恢复过程中,草本层丰富度指数(Margalef指数)、Shannon-Wiener指数和均匀度指数(Pielou指数)高于乔木层和灌木层,群落物种多样性呈波动式变化,恢复21年群落Margalef指数和Shannon-Wiener指数最高,恢复13年群落Pielou指数最高。植被恢复过程中群落多样性指数均高于天然白桦林。2)植被恢复过程中群落生物量为10.80~123.96 t/hm2,随恢复年限的增加逐渐增大,恢复21和24年群落生物量高于天然白桦林。草本层生物量占群落生物量比例最低,恢复3年群落枯落物层蓄积量占群落生物量比例最高,其余恢复年限乔木层生物量占群落生物量比例最高。3)乔木层Margalef指数与生物量呈极显著正相关。灌木层Shannon-Wiener指数和Pielou指数与生物量呈极显著负相关,Pielou指数与生物量相关系数最高。草本层多样性与生物量相关性不显著。群落Shannon-Wiener指数与地表生物量呈极显著负相关。由此可知,人工更新灌木层和草本层多样性恢复效果优于天然更新,人工更新恢复21和24年的生物量恢复效果优于天然更新,植被恢复过程中植物多样性和生物量存在一定相关性。 相似文献
97.
Micromorphological Features of Old Cultivated and Modern Soils in Guanzhong Areas, Shaanxi Province, China 总被引:2,自引:1,他引:2
PANG Jiang-li HU Xuan-er HUANG Chun-chang Zhang Xu 《中国农业科学(英文版)》2006,5(9):691-699
Using the data obtained from the LGT soil profile, this article attempts to illustrate the process of modem soil formation in the Guanzhong areas and its micromorphological features. The micromorphology is observed under a petrographic microscope, and its image is quantitatively measured by LEICAL Qwin 2.6 software. Micromorphological observations of the thin sections show that the assemblage of minerals in different horizons is very similar, which is mainly composed of Q and P1. However, there are obvious differences in C/F15μm ratio, mineral content, and coarse features. The pedofeatures is mainly composed of clay, calcite, and amorphous Fe. Ap horizon is characterized by abundant needleshaped secondary calcite, secondary clay, and earthworm fecal pellet. BC horizon is characterized by a large quantity of secondary calcite with various shapes. Bt1and Bt2 horizons are characterized by abundant clay hypocoatings and a small quantity of secondary calcite. All the results of this research suggest that Earth-cumulic Orthic Anthrosols consist of both the upper Ap horizon, which cause loessal dung and eolian dust deposition, and cultivation occurs simultaneously during the process of Ap horizon-formation, and the lower BC horizon, which is aeolian sedimentary at the time of relative aridity during late Holocene. 相似文献
98.
LI Shao-kun SUO Xing-mei BAI Zhong-ying QI Zhi-li Liu Xiao-hong GAO Shi-ju ZHAO Shuang-ning 《中国农业科学(英文版)》2002,1(8):885-889
Recognition and analysis of dynamic information about population images during wheat growth periods can be taken for the base of quantitative diagnosis for wheat growth. A recognition system based on self-learning BP neural network for feature data of wheat population images, such as total green areas and leaves areas was designed in this paper. In addition, some techniques to create favorable conditions for image recognition was discussed, which were as follows: (1) The method of collecting images by a digital camera and assistant equipment under natural conditions in fields. (2) An algorithm of pixei labeling was used to segment image and extract feature. (3)A high pass filter based on Laplacian was used to strengthen image information. The results showed that the ANN system was availability for image recognition of wheat population feature. 相似文献
99.
为了解喀斯特山区2个不同鲫鱼群体在蛋白质水平的遗传多样性及其遗传差异,运用聚丙烯酰胺凝胶电泳方法对喀斯特山区2个群体鲫鱼的血清转铁蛋白电泳表型及多样性进行研究。结果表明:群体克隆多样性指数表现为草海鲫鱼(0.32)﹥红鲫(0.25,对照)﹥普安鲫鱼(0.13);3个鲫鱼群体的13个克隆由9个不同的等位基因产生,等位基因的频率分别为Tf~a0.144 9、Tf~b0.202 9、Tf~c0.036 2、Tf~d0.058 0、Tf~e0.007 2、Tf~f0.239 1、Tf~g0.014 5、Tf~h0.275 4、Tf~i0.029 0;普安鲫鱼与草海鲫鱼和红鲫无共享的基因型;普安鲫鱼与草海鲫鱼之间的遗传相似性指数较高(0.714 3),遗传距离较小(0.285 7)。总体来看,草海鲫鱼的克隆多样性水平较高,其转铁蛋白多样性程度较普安鲫鱼丰富;2个群体之间存在较近的亲缘关系,未达到遗传距离种的分化标准。 相似文献
100.
Among a vast number of forage trees, Vachellia karroo (Acacia karroo) remains one of the most widely distributed indigenous plant legumes in Southern Africa. The plant possesses some striking attributes, such as rapid growth rate, drought tolerance, adaptation to alkaline and acidic sterile soils, and resistance to a variety of edaphic and temperature changes. In past years V. karroo was recognised to be a major threat to rangeland productivity owing to its invasive nature. Research interest has shifted from its eradication as an unwanted plant to its utilisation as a feed resource for livestock. Extensive utilisation of V. karroo is mainly hindered by the presence of tannins and spines. Prospects to lessen the adverse effects of the anti-nutritional influences are now recognised. Vachellia karroo possesses desirable fatty acid profiles, and high protein and mineral contents that can improve animal performance. Presently, the use of V. karroo for goat production in communal areas is restricted owing to limited evidence for its nutritional value as animal feed. The present review, therefore, seeks to demonstrate the utility potential of V. karroo to improve growth performance, carcass characteristics, chevon quality, meat fatty acid profiles and as a natural anti-helminth for goats raised under an extensive system of production. 相似文献