浑善达克沙地榆树径向生长特性

Radial growth characteristics of Ulmus pumila var.sabulosa in Otindag sand land,northern China

以位于浑善达克沙地宝绍岱苏木和那日图苏木的天然沙地榆为材料,测定沙地榆的年轮宽度、早材宽度和晚材宽度,分析其偏心生长状况、径向生长规律和径向生长动态,为浑善达克沙地榆树种群保护和天然更新提供依据。结果表明：宝绍岱和那日图生长的沙地榆均存在不同程度的偏心生长,且偏心形态比较复杂,形状不规则;宝绍岱和那日图沙地榆的径向生长过程中均出现了2个生长高峰期,其中年轮宽度和晚材宽度的径向生长规律非常相似,2次高峰期出现的时间完全一致,径向累积生长曲线均呈双S型;早材宽度在整个生长过程中的变化幅度很小,高峰期出现的时期与年轮宽度和晚材宽度相差比较大,累积生长曲线呈线型;宝绍岱和那日图沙地榆的平均生长量分别为2.25和2.30 mm,无显著差异,但宝绍岱沙地榆年轮宽度和晚材宽度的变异系数达到20%以上,明显大于那日图沙地榆;宝绍岱沙地榆径向生长第1次高峰出现在第17-21年,那日图沙地榆径向生长第1次高峰出现在第15-19年,二者的成熟龄相差3年。

Ulmus pumila var. sabulosa specimens were collected from natural forests located in Baoshaodai and Naritu of Otindag sand land northern China. To provide a basis for the population conservation and natural regeneration of elms in Otindag sand land,tree-ring width,earlywood width and latewood widthwere measured to study their eccentric growth and radial growth. The results showed that elms in Baoshaodai and Naritu had different degrees of eccentric growth with complicated eccentric forms and irregular shapes. Elms in both Baoshaodai and Naritu had two growth peaks in the ring widths. Tree-ring width and latewood width had a similar double ＂S＂growth pattern and their growth peaks occurred in exactly the same time. In contrast,earlywood width had little change during the whole growth period.Earlywood width had different growth peaks from annual ring width and latewood width, and the cumulative growth curve of earlywood width was linear. There was no significant difference in average annual growth of elms between Baoshaodai and Naritu,which were 2. 25 mm and 2. 30 mm respectively.Tree-ring width and latewood width of elms in Baoshaodai had a variation coefficient of 20%,which was much higher than that in Naritu. The first radial growth peak of U. pumila var. sabulosa in Baoshaodai occurred in the year 17 to 21 while that in Naritu occurred in the year 15 to 19. The mature age of U.var. sabulosa in the two places differs by 3 years.