中国西北小叶杨资源概述

An Survey for Populus Simonii Resources in Four Provinces of Northwest China

小叶杨是我国特有乡土树种，小叶杨抗风沙，耐瘠薄，在砂荒及黄土高原能生长，最适宜的则是湿润肥沃的黄土和冲积土，是培育“三北”地区新栽培无性系的最佳亲本之一。作者调查西北４ 省，发现沿山系的沟谷、河滩还大量生长着小叶杨，它们大多是５０～６０ 年代用种子繁殖的人工林，百年小叶杨老树很少见。荒凉贫瘠的沟谷、河滩地上的小叶杨比其它树种，比其它杨树品种生长得好，是一些林场重要的经济来源。这些小叶杨形态各异，蕴藏着丰富的基因资源。

Populus simonii is one of the most important native tree species in China, and widely distributed from Heilongjiang (north)to Sichuan (south),and from Liaoning (east) to Qinghai(west) and endure to drought conditions. It is an xerophilous species in slight wet forest steppe belt with various phenotypes, and a lot of variants or other species are classified within the species by taxonomist. In the natural range of P. simonii ,the temperature changes sharply and the maximum and minimum temperatures are 43℃ and -41℃ respectively. Its dry atmosphere, maximum and minimum temperatures enduring is more than that of other species in P. Cathayana section. It has thick and long main roots and small and thick leaves with small cells on the surface, close mesophyll tissue, few stoma, and dense vein, wooden rashes on the twigs etc. P. simonii is not only one of the important tree species and widely cultivated in north (including north, northeast and northwest of China),but also a best parent of the superior clones planted in the region. As the woods go to wreck, farmland is enlarged and only few clones are planted,the natural P. simonii resources disappeared rapidly. It is reported that some provinces are without any individuals of the species. Since little was known about P. simonii resources in China, the anthors surveyed the P. simonii resources in four provinces (Qinghai, Gansu, Shanxi and Ningxia) in the northwest of China. According to the investigation on P. simonii in the four provinces,the leaves are large or small inverted ovums, the branches are pendence or holding up. The detailed diversification′s in morphology and genetics will be studied in the near future. Ms. Yang Zixiang is from Chinese Academy of Forestry, Beijing 100091, China.