为了解旱季不同降水变化对白枪杆幼苗生长及根系形态特征的影响,在旱季采用人工模拟降水试验,研究白枪杆幼苗生长及根系形态特征对降水变化的响应。结果表明:1)旱季第一阶段(每年11月至次年1月),当降水间隔时间相同时,白枪杆幼苗的地下生物量、总生物量、根冠比、总根长、根表面积随降水量的增加而增加;当降水量相同,降水间隔时间由5 d(T)延长至10 d(T+)时,总根长、根表面积、根体积、比根长均在减小;2)旱季第二阶段(每年2月至4月),在同一降水间隔时间下,白枪杆幼苗的总根长随降水量增加呈先上升后减小的趋势;在降水量相同的情况下,地上生物量随降水间隔时间的延长而增加;3)不同降水量变化处理下,白枪杆幼苗的总根长随旱季时间的延长而不断增加,根表面积、根体积、平均根直径、比表面积随旱季时间的延长而逐渐减小。本研究表明,在不同降水变化试验中,降水量为主要影响因素,降水间隔时间起辅助作用,二者互相依赖。随着旱季时间的延长,白枪杆幼苗的生长及根系形态特征机制会对降水量变化产生不同的响应。

To investigate the effects of varying precipitation patterns on the growth and root morphological characteristics of Fraxinus malacophylla seedlings during the dry season,artificial precipitation simulation experiments were conducted.1)During the first stage of the dry season(November to the next January),belowground biomass,total biomass,and root-crown ratio,total root length,and root surface area increased asprecipitation levels rose;provided the precipitation interval remained constant.However,when the precipitation interval was extended from 5-day intervals(T)to 10-day intervals(T+)underthe same precipitation,the total root length,root surface area,root volume,and specific root length all decreased.2)During the second stage of the dry season(February to April),total root length initially increased and then decrease as precipitation levels rose,given a constant precipitation interval.Aboveground biomass increased with prolonged interval at the same total precipitation level.3)Under different precipitation treatments,total root length consistently increaseed over the course of dry season,whereas root surface area,root volume,average root diameter,and specific root length gradually decreased.This study demonstrated that precipitation was the primary factor in the different precipitation change experiments,and the precipitation interval played a secondary role,and they were interdependent.The mechanisms of seedling growth and root morphology characteristics of Fraxinus malacophylla responded differently to the precipitation change with the duration of the dry season.