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一、前言营造农田防护林带是人工改造小气候极为有效的一种措施。农田林网在维持生态平衡,防止或减轻灾害性天气对农业的危害,保证农业稳产、增产方面发挥着重要作用。国内外的研究证实,林网能为作物生长发育创造有益的生态环境,使作物产量和质量都有提高。林网在干旱、半干旱、半湿润地区,使作物可增产10～30%;在湿润地区可增产5～20%。此外,林网在解决木材紧缺方面的作用也不可忽视。农田林带的各种效益同它的结构、营造技术有直接关系。我省自然地理条件较复杂,农业灾害频繁。陕北的风沙,渭北及关中平原的干热
I. INTRODUCTION Creating farmland shelterbelts is an extremely effective measure to artificially transform the microclimate. Farmland forest network plays an important role in maintaining ecological balance, preventing or reducing the harm of disastrous weather to agriculture, and ensuring stable agriculture and increasing production. Research at home and abroad has confirmed that forest net can create a beneficial ecological environment for the growth and development of crops and improve crop yield and quality. Lin network in the arid, semi-arid and semi-humid areas, crops can increase 10 to 30%; in wet areas can increase 5 to 20%. In addition, the role of the forest network in addressing the shortage of wood can not be ignored. Various benefits of farmland forest belt with its structure, creating technology is directly related. Natural and geographical conditions in our province are more complicated and agricultural disasters are frequent. Wind and sand in northern Shaanxi, dry and hot Weibei and Guanzhong Plain