西昌、凉山地区东西河流域是四川飞机播种造林最早的地区。本区位于北纬27°40′—28°20′,东径102°10′—102°40′。地处云贵高原北部,属台地地貌。受印度洋季风强烈影响,干湿季明显。年平均气温17℃,最冷月气温9.5℃,极端最低气温-3.4℃,最热月22.7℃,极端最高36.5℃;年平均相对湿度61％,无霜期250天以上;年雨量1,000毫米左右,分配不均。年蒸发量约2,000毫米,为降雨量的2倍。11月至次年5月为旱季,降雨量只占年雨量的7％,蒸发量1,100毫米,为同期降雨量的15 Xichang, Liangshan area Dongxi River Basin is the earliest planting area of ​​Sichuan aircraft planting. The area is located at latitude 27 ° 40’-28 ° 20 ’and with an east diameter of 102 ° 10’-102 ° 40’. Is located in the northern Yunnan-Guizhou Plateau, is a landform. Strongly affected by the Indian Ocean monsoon, wet and dry season significantly. Annual average temperature of 17 ℃, the coldest month temperature of 9.5 ℃, the extreme minimum temperature of -3.4 ℃, the hottest month 22.7 ℃, extreme maximum 36.5 ℃; annual average relative humidity of 61%, frost-free period of 250 days or more; annual rainfall of about 1,000 mm, the distribution Uneven. Annual evaporation of about 2,000 mm, twice the amount of rainfall. November to next May is the dry season, rainfall accounts for only 7% of annual rainfall, evaporation 1,100 mm, the same period rainfall 15