甘肃中部干旱区退耕还林预设目标与现实差异研究—基于甘肃省定西市安定区的调查   总被引：2，自引：0，他引：2  

丁文广  胡小军  卜红梅 《干旱区资源与环境》2004,(Z2)

在 2 0 0 4年国家退耕还林政策做出大幅调整之时 ,本文研究者选择甘肃省中部干旱农村社区进行了深入调查研究 ,以退耕还林预设目标与现实差异的研究为切入点 ,反观和反思退耕还林政策。同时 ,作者以政策执行的互动理论模式为依据 ,指出造成退耕还林目标与现实较大差异的根本原因在于公众的参与机制在环境政策决策与实施过程中的缺失 ,并提出相应的建议 ,以期促进和推动退耕还林政策的完善与改进。  相似文献   

黑痣菌属的研究     

黄天章  黄奕冲 《福建林学院学报》1992,12(4):371-375

本文研究黑痣菌属的特征,描述种的划分。在调查林木病害过程中,发现一个新种,命名为Phyllachora aquifotia Huang ＆G.sp.nov.增加该属的一个新的分类单位。  相似文献   

草坪在改善城镇环境中的地位和作用   总被引：7，自引：4，他引：7  

萧运峰 《四川草原》1997,(2):28-32

本文指出了当前城镇环境恶化的严重性，防治环境污染和气候荒漠化的重要性及紧迫性。详细阐明了草坪在绿化、美化、净化城镇环境和调节城镇气候中的地位和作用  相似文献   

Effects of nitrogen application rate on productivity,nutritive value and winter tolerance of timothy and meadow fescue cultivars     

Maarit Termonen  Panu Korhonen  Sanna Kykkänen  Anna Kärkönen  Minna Toivakka  Raimo Kauppila  Perttu Virkajärvi 《Grass and Forage Science》2020,75(1):111-126

Finnish N fertilizer application regulations for forage grasses are based on field experiments mainly conducted in the 1960–1970s with cultivars and management practices typical of the time. In order to update the yield response function of N, to make it better suited to current grassland farming, field experiments were conducted at two sites in 2015–2017 with two cultivars of timothy (Phleum pratense L.) and one of meadow fescue (Festuca pratensis Huds.). Dry matter (DM) yield, nutritive value and N balance were evaluated, with N application levels 0, 150, 200, 250, 300, 350, 400 and 450 kg N ha⁻¹ year⁻¹. The grasses were harvested three times per season. The data indicate that the DM yield response was significantly stronger, and N was used more efficiently for DM production than earlier without compromising the nutritive value, especially during the first two years. The third harvest produced on average 23% of the annual yield, utilizing N efficiently. N application rates below 350 kg N ha⁻¹ year⁻¹ did not cause substantial overwintering losses or lodging. The data indicate that with changing climate and improved cultivars and management practices, there is a need to modify the rates and timing of N application. The results suggest that N application levels could be increased by at least 50 kg N ha⁻¹ year⁻¹ from the current maximum accepted rate (250 kg N ha⁻¹ year⁻¹) without too high NO₃^- or CP concentrations in feed, or too high N balance that indicates increasing risk of N leaching.  相似文献   

Biomass production of trees and grasses in a silvopasture system on marginal lands of Doon Valley of north-west India. 1. Performance of tree species     

M. K. Vishwanatham  J. S. Samra  A. R. Sharma 《Agroforestry Systems》1999,46(2):181-196

Bouldery riverbed lands occupy about one-third of the geographical area in Doon Valley of north-west India. These marginal lands need rehabilitation through establishment of silvopasture system for meeting the biomass requirements of resource-poor farmers. A study was carried out for 14 years (1980 to 1993) at Dehradun, involving four multi-purpose tree species viz. Albizia lebbek (L.) Benth., Grewia optiva Drumm., Bauhinia purpurea L. and Leucaena leucocephala (Lamk.) de Wit.; and two grass species viz. Chrysopogon fulvus (Spreng.) Chiov. and Eulaliopsis binata (Retz.) C.E. Hubb. Fifty and 75% of the tree crown was lopped once a year after four years of age. Tree survival decreased with age, and was highest with L. leucocephala (86.9% in 1993 of initial density of 625 trees ha⁻¹) and lowest with B. purpurea (49.3%). Canopy parameters of trees progressed differently, presumably due to their varying growth habits. The trees of A. lebbek were taller with more crown spread, whereas G. optiva had more crown height with lesser crown spread. Stem diameter growth of A. lebbek was highest followed by B. purpurea. Lopping intensity did not affect tree survival and also canopy growth in most years, but collar diameter and diameter at breast height (dbh) decreased significantly at the higher intensity of lopping. Intercropped grass species E. binata caused a greater adverse effect on the tree survival and growth parameters than C. fulvus. The biomass production (leaf and branch wood weight of lopped material) was highest at eight years of age in 1987 but showed no definite trend over the study period. Bauhinia purpurea produced the highest biomass and L. leucocephala the lowest, despite opposite trends in their survival. The performance of A. lebbek was on par with B. purpurea in the later years (1990--1993), but G. optiva was inferior despite its superiority in the early years (1984--1985). The effects of lopping intensity were not appreciable, but intercropping with E. binata decreased leaf and branch wood production significantly compared with C. fulvus throughout. However, the adverse effect was comparatively less pronounced on B. purpurea and A. lebbek than on G. optiva and L. leucocephala. The fibre yield of G. optiva also decreased due to intercropped E. binata compared with C. fulvus. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

能源草新品系桂能草1号特征特性及高产栽培技术研究     

覃维治  李韦柳  兰生葵  韦民政  郑虚  唐秀桦  熊军  闫海锋 《安徽农业科学》2014,(19):6188-6189,6192

能源草新品系桂能草1号是广西农业科学院经济作物研究所从国外引进的杂交狼尾草资源中经过多年选育出的能源专用型新品系.该品系和传统的牧草相比,生物产量和纤维素含量高;一年两收,一茬生育期约为150 d,适应性广,生长快,再生性强,抗逆性强;品比试验表明,其年干物质产量平均达到77.93 t/hm2,生物产量生产潜力巨大;经广西分析测试中心分析测定,干物率为36.3％,纤维素含量为57.0％,半纤维素含量为7.44％,热值高高达18.49 MJ/kg,灰分2.84％.桂能草1号新品系在南方大部分地区种植良好,由于既可以转化为乙醇,又可以制成固体燃料代替煤,所以有望成为我国南方优良的能源型纤维类草本作物.主要分析新品系桂能草1号的生物学特征,总结其高产栽培技术,为该品系发展生物质能源提供技术支持.  相似文献   

加拿大披碱草与肥披碱草杂种F1的形态学及细胞学研究   总被引：9，自引：3，他引：9  

于卓 王晓娟刘杰  马艳红 《麦类作物学报》2004,24(4):6-10

为了解加拿大技碱草与肥技碱草杂种F1的育性状况、细胞遗传学基础和育种潜力，用定株观测、花粉染色、染色体制片镜检等方法，对杂种F1的生育特性、染色体构型等进行了研究。结果表明，杂种F1植株生长势很强，生长速度和株高明显超过其双亲，株型倾向母本加拿大技碱草，穗较长，穗型呈中间型，叶片宽大，花粉可育率及结实率均为0；F1为五倍体(2n=5x=35)，其PMCMI平均染色体构型为5．79Ⅰ 14．3Ⅱ 0．17Ⅲ，后期Ⅰ出现染色体桥和落后染色体。  相似文献   

割草机机具参数对抛撒碎草的影响     

单春贤  方攀  邵霞 《农机化研究》2009,31(4)

割草机电机转速和割草线的长短是抛撒碎草的主要影响因素之一.为了研究割草机流道内部机具参数对抛撒碎草的影响,采用直径为39mm的透明有机玻璃保护罩,以直径为1mm的ABS塑料作为实验割草线并变为半长,在电机转速分别为2500 r/min和3500 r/min的情况下,利用粒子图像测速技术(PIV)结合数值模拟,对割草机内部流场的特性进行了研究.  相似文献   

~(15)N天然丰度法测量豆科牧草共生固氮的评估   总被引：2，自引：1，他引：2  

姚允寅  陈明  马昌燐  王志东  侯景琴  张丽红  骆永云 《核农学报》1991,5(3):139-145

无氮营养液砂培7个品种苜蓿茎叶的固氮分馏因数β值为1.0000～1.0015(δ~(15)N为-0.05～-1.47‰),白三叶、绿豆和银合欢的β值分别为0.9979、0.9983和1.0018(δ~(15)N分别为2.15、1.74及-1.81‰)。根据~(45)N天然丰度的变化,估测了田间生长苜蓿的固氮能力,表明6个品种的共生固氮能力不同。格洛里及润布勒苜蓿两品种最高,保定、阿尔贡奎因及明托苜蓿3个品种次之,秘鲁苜蓿最低。苜蓿不同时期的固氮活性有变化,6、7月间固氮活性达高峰。根据所测豆科牧草茎叶的δ~(15)N值,可以对豆科牧草进行定性或半定量水平上的固氮研究,以筛选高效固氮牧草和检测野生固氮资源。本文还对不固氮参照植物和不同方法对％Ndfa估计位的影响进行了讨论。  相似文献   

黄土高原水土流失区退耕还林(草)的基本思路   总被引：16，自引：1，他引：16  

彭珂珊 《水土保持研究》2000,7(2):164-171

朱总理针对1998年我国水土流失加剧而致使洪灾造成2251亿元人民币巨大损失的现实,于1999年8月提出了“退耕还林（草）、封山绿化、个体承包、以粮代赈”的措施,为根治黄土高原的水土流失和良化我国的生态环境指明了方向。文章在上述背景下分析了我国黄土高原地区坡耕地引起水土流失、肥力低下、水源缺乏、灾害频繁的四大问题,根据黄土高原的生态环境脆弱的具体情况,提出了以下几条对策:1 提高思想认识;④解决好退耕后脱贫;（四）推进东西部合作政策;1/4保证人均一定的农田;1/2实现农林牧业最佳结合;3/4提出合理的措施;⑧健全保障机制;（七）正确处理各种关系。研究的基本思路可供同类地区的干部和群众为退耕还林（草）,搞好植树造林,治理水土流失,脱贫致富,建设秀美山川作出贡献。  相似文献