宁南旱区苜蓿草地土壤水分和根系动态分布拟合曲线特征

试验以宁南旱区3、4、6、7、10、12年生紫花苜蓿草地为研究对象,利用空间替代时间的方法,分别对紫花苜蓿的生长年限与土壤水分、根系深度和土壤干层厚度之间关系作出拟合曲线方程,以揭示土壤水分、根系和土壤干层随苜蓿生长年限变化的动态规律.结果表明:不同生长年限苜蓿土壤剖面含水率分布与土壤深度之间均呈二次曲线函数关系,且随...

Study on curve fitting features of soil moisture and root system's dynamic distribution in alfalfa grassland in drought areas of southern Ningxia

From 2004 to 2005 year,investigation experiments were conducted on 3,4,6,7,10 and 12-year-old alfalfa grassland in drought areas of southern Ningxia by space alternative time method to match curve equations between alfalfa growth year and soil profile moisture content,as well as root depth and soil dry layer thickness respectively,aiming to identify dynamic change laws of soil profile moisture content,roots depth and dry layer thickness with increasing alfalfa growth age.Results show that,for all different growth year alfalfas,there is a quadratic curve functional relation between soil profile moisture content and soil layer depth,and its functional curve graphs show regular dynamic distribution with alfalfa growth year change.During the previous 10 years of alfalfa growth,its roots depth increases by 35.33 cm per year and soil dry layer thickness increases by 91.43 cm per year.During alfalfa decay after 10 years,soil dry layer thickness decreases by 20.77 cm per year,i.e.,the speed of soil dry layer formation is 4.40 times that of fading.Therefore,it is difficult to recover if soil dry layer is formed.The 6th and 10th year of alfalfa growth featuring water fastigium and decay period respectively indicate they are the two critical periods of alfalfa growth.This paper suggests that alfalfa optimum growth age is 6-year-old and no later than 10-year-old.