紫花苜蓿和短花针茅根系分布与土壤水分研究

以陕北农牧交错带人工草种紫花苜蓿(Medicago sativa L.)和天然草种短花针茅(Stipa breviflora Griseb.)为对象,采用根钻法调查两个草种的根系垂直分布以及刈割后苜蓿根系变化特征,并通过定位观测研究土壤水分动态变化。结果表明:紫花苜蓿和短花针茅根系密度随土壤深度增加而减少,而且均以直径小于等于1 mm的须根为主;0~50 cm土层紫花苜蓿和短花针茅根系量分别占0~100 cm剖面总量的67%和84%。紫花苜蓿和短花针茅根系分布与土壤水分消耗特征吻合。生长旺盛期苜蓿大量消耗0~140 cm土层土壤水分,5-9月平均有效土壤储水不足10 mm;生长季末深层(140~280 cm)土壤储水也逐渐降低,约为裸地储水量的50%。短花针茅0~280cm剖面土壤水分状况明显好于苜蓿地,比苜蓿地多储水100 mm左右;主要消耗浅层(0~50 cm)土壤水分,深层水分利用较少。

Root Distribution and Soil Water Dynamics of Medicago sativa L. and Stipa breviflora Griseb.

Vertical root distributions of Medicago sativa L. and Stipa breviflora Griseb.were investigated using drill method and soil water dynamics were studied by positioning field observation in the farming-pastoral interlaced region of northern Shaanxi province.The results show that root densities of M.sativa and S.breviflora decreased along with the increased soil depth,and the diameter of most roots was within l mm.The percentage of M.sativa and S.breviflora roots in 0-0.5 m soil layer were 67% and 84% of the total root amount throughout 0-1.0 m profile,respectively.Soil water used by M.sativa and S.breviflora were greatly affected by their roots distribution in profile.Water stored in 0-140 cm soil layer was depleted mainly by M.sativa;the averaged plant available water was less than 10 mm from May to September;in deep soil layer of 140-280 cm,soil water storage also declined gradually at the end of the growing season and was about 50% of that in bare land.Water stored in 0-280 cm soil layer under S.breviflora was 100 mm more than that under M.sativa.Soil water consumed by S.breviflora was mainly from 0-50 cm soil layer,and little soil water consumption was observed in deep soil layer.