雁门关林扬位于山阴县境内,除山区经营针叶林、桦树林外,平川还经营小叶杨6820亩。分布于山阴县后所乡、张庄乡境内。海拔1030m,年降雨量400mm 左右,土壤瘠薄而干旱,偏碱性。由于人为破坏,这片林子多次萌生,加之经营粗放,普遍生长衰退,有的已停止生长成了“小老树”。经调查30年生的林分5812亩,平均高9m,平均胸径11cm,亩蓄积仅有1.74m~3,平均生长率为5.8％。面对效益不高的问题,五台林局从1980年开始就在雁门关林场逐步对“小老树”进行了改造。引进抗盐碱性强的优良品种小黑杨,合作杨、群众杨更替小叶杨。到1989年 Yanmenguan Lin Yang is located in Sanin County, in addition to operating coniferous forests in the mountains, birch forests, Hirakawa 6820 acres of Populus lobata. Distributed in Sanin County Township, Zhang Zhuang territory. Elevation 1030m, the annual rainfall of about 400mm, barren and arid soil, alkaline. Due to man-made destruction, this piece of wood sprout many times, combined with extensive management, the general decline in growth, and some have stopped growing into a “small tree.” After surveying 30-year-old stands of 5812 mu, the average height is 9m, the average diameter at breast height is 11cm, and the stock of mu is only 1.74m ~ 3 with an average growth rate of 5.8%. In the face of the problem of low benefit, the Wutai Forestry Bureau gradually reformed the “Little Old Tree” in Yanmenguan Forest Farm from 1980 onwards. The introduction of good anti-salinity and good varieties of black poplar, Yang cooperation, the poplar Yang replacement poplar. By 1989