小叶杨(Populus simonil Carr),陕北群众叫水桐、冬瓜杨、白达杨,是一种分布面广、适应性强、生长较快、材质较好的优良树种。小叶杨也是我国分布最广的杨树之一。北至黑龙江、吉林、辽宁、内蒙古、山西、河南、山东、江苏;南至四川、湖南、云南;西至新疆、青海、甘肃、宁夏等省、区均有分布。垂直分布高达海拔3000米,以1500米左右为宜。陕西省各地均有分布,但以渭北黄土高原地区分布较多,是群众喜爱的“四旁”绿化树种,也是天然林区一个重要的森林树种。陕北的劳山、桥山、黄龙山及陕西西部的关山,小叶杨分布较广,多生 Populus simonil Carr, northern Shaanxi masses called water-melon, melon, poplar, is a widely distributed, adaptable, fast-growing, better quality fine tree species. Populus is also one of the most populous poplars in our country. North to Heilongjiang, Jilin, Liaoning, Inner Mongolia, Shanxi, Henan, Shandong, Jiangsu; south to Sichuan, Hunan, Yunnan; west Xinjiang, Qinghai, Gansu, Ningxia and other provinces and regions are distributed. Vertical distribution of up to 3000 meters above sea level, preferably 1500 meters. Shaanxi Province is distributed all over the country, but distributed more in the Weibei Loess Plateau. It is a favored “four sides” green tree species and an important forest tree species in natural forest areas. Laoshan, Qiaoshan, Huanglong Mountain in northern Shaanxi and Guanshan in western Shaanxi Province, Populus simonii is widely distributed, with many students