大针茅根系构型对草地退化的响应

本研究对锡林郭勒典型草原区轻度、中度、重度和极度4个退化梯度草地中大针茅(Stipa grandis)根系构型进行研究。结果表明，1）根分叉数、根表面积和总根长3个参数是分析大针茅根系构型在不同退化程度草地中变化的主要指标，其中根分叉数对该变化的解释力最强，3个参数的累积贡献率为90.7%;2）从轻度、重度到极度退化程度的草地系列中，大针茅的根系构型小型化趋势明显;3）中度退化程度的草地中大针茅根系构型小型化特别明显;4）根系构型小型化最终导致整个植物体小型化，因此在群落退化演替进程中大针茅的建群种作用逐渐减弱并最终为其他优势种取代。

Responses of the root architecture of Stipa grandis to grassland degradation

The study was conducted to investigate responses of root architecture of Stipa grandis grown under different grassland degradation levels(light,medium,high and extreme) in Xilin Gol League.The relative completed roots of S.grandis were collected by trenching and analyzed by using the root analysis system of WinRHIZO to determine total root length,root surface area,total root volume,root average diameter,number of root tips,number of furcation and average branching angle,number and length of first vertical root,number and length of first lateral root,number and length of secondary lateral root,number of adventitious root.The data obtained was analyzed by one-way ANOVA and principal component analysis.The results indicated that 1) the number of furcation,the surface area of root and the total length of root were the preferred indexes for analyzing S.grandis’ variation to grassland degradation,while the number of furcation had the strongest explanation strength of the indexes to the variation.The cumulative contribution rate of the three root architecture indexes was 90.7%.2) With the degradation development from light to extreme,the root architecture of S.grandis was obviously miniaturized.This phenomenon was especially obvious in medium degradation grassland.3) The miniaturized root architecture of S.grandis eventually led to miniaturization of the entire plant,so the role of S.grandis as constructive species in the succession process of the community degradation was gradually weakened and finally replaced by other dominant species.