坦桑尼亚木材供应及木材可持续生产

2005年第4期《国际林业述评》报道了坦桑尼亚的木材供应及木材可持续生产。在非洲撒哈拉地区，城市的发展给森林资源带来了新的压力，大多数贫困家庭依靠木材来满足对住房和家具的基本需求。林业和木材工业为城市和农村地区很多人提供了就业机会。据官方估计，坦桑尼亚有73万人从事林业。另据非官方的调查统计，坦桑尼亚有15．7万人从事木材产品生产，其中近11．7万人生活在农村，约4万人生活在城镇。因此，保证木材的充足供应成为维持生活和遏制贫困的关键因素。[第一段]     

贵州省苗疆腹地森林旅游资源

贵州省森林旅游资源丰富,笔者对独具民族特色的苗疆腹地森林旅游资源进行了研究。     

典型流域土壤侵蚀演变的高程、坡度空间差异比较

三峡库区腹地作为生态环境脆弱和土壤侵蚀敏感地区,其土壤侵蚀研究对库区生态建设具有重要意义。选取大宁河和梅溪河流域,借助GIS和RS技术,以1988,2000,2010,2015年遥感影像为数据源,结合实地调查,提取土壤侵蚀数据,通过土壤侵蚀强度综合指数、景观格局指数等研究方法,分析其不同高程、坡度带土壤侵蚀演变空间差异,探究土壤侵蚀防控的措施。结果表明:(1)从土壤侵蚀严重程度来看,2个流域最严重土壤侵蚀带及其演变趋势均具有较大的差异性。大宁河流域1 000~1 200m范围内的25°~35°坡度带最为严重,梅溪河流域则以800~1 000m范围内的25°~35°坡度带最为严重;(2)从土壤侵蚀演变程度来看,两流域土壤侵蚀演变程度快慢存在一定的差异性。大宁河流域以2 000 m高程带和35°坡度带演变最明显,200m和5°坡度带最不明显;梅溪河流域则以1 000~1 200m高程带和25°~35°坡度带演变速度最快,200m和5°坡度带最不明显;(3)从土壤侵蚀景观格局演变特征来看,在800~1 200m高程带和25°~35°坡度带,大宁河流域土壤侵蚀剧烈程度可能性大于梅溪河流域。以上研究结果,为后续对两流域800~1 200m高程带不同坡度、25°~35°坡度带不同高程的土壤侵蚀空间分布规律以及主控自然因子与土壤侵蚀的相互关系等科学问题的研究奠定了基础。     

沙漠腹地盐水灌溉条件下蔬菜种植技术初探

沙漠腹地盐水灌溉条件下种植蔬菜首先要建立防风固沙体系,在基础上对20种蔬菜进行适应性筛选，选出西葫芦、甜瓜、茄子等9种适应性较强的蔬菜并建议推广。同时，摸索出沙漠腹地盐水灌溉条件下蔬菜种植的关键技术：育苗移栽，苗期集中管理；底肥大量施用腐熟有机肥，追肥少量勤施；喷灌与漫灌相结合，以水压盐；植株精细调整，协调营养生长和生殖生长等。     

Impediments to New Improved Maize Variety Testing and Release in Selected Countries in Sub-Saharan Africa

Before farmers can benefit from new improved maize varieties with novel genetic information, new maize varieties have to undergo performance testing, registration and approval. The registration procedures require that new maize varieties must pass the tests for value for cultivation and use （VCU） and standardized tests for distinctness, uniformity and stability （DUS）. To meet the minimum requirements for variety release, public and private sector maize breeding programs routinely assemble breeding nurseries and evaluate variety performance in National and Regional Performance Trials （NRPT） with the objective of generating important agronomic data to identify the best maize varieties for release. In spite of intensive variety evaluation in regional and national trials, only few maize varieties have been registered and released annually in sub-Saharan Africa （SSA） denying farmers access to new improved varieties. The purpose of this study was to identify constraints hampering the registration and release of elite maize gennplasm and make recommends on how to quicken the deployment of elite germplasm to smallholders＇ farmers. A survey was conducted on the varietal testing and release systems in 14 selected countries （Angola, Benin, Ethiopia, Malawi, Ghana, Mali, Mozambique, Nigeria, Tanzania, Kenya, South Africa, Uganda, Zambia, and Zimbabwe） in SSA. The results from the study show that regulations on variety testing and release procedures in the various countries are overlapping and rigid hindering the deployment and commercialization of new improved maize germplasm. The study also showed that varietal release rates fluctuated between countries with South Africa having the highest number of varietal release rates per year and some countries failing to release a single variety per year.     

以色列人这样种菜

正提到以色列现代沙漠农业,其滴灌技术令人咂舌。不可思议的是,这个弹丸小国居然在沙漠上种出世界上屈指可数的无污染洁净蔬菜,还大量出口国外。目前,以色列食品在国际上信誉有口皆碑,赢得欧洲冬季厨房的美名。洒水施肥全由电脑控制以色列60%土地属于干旱或半干旱地区,大多