Response of Ecological Properties of Roots of Alhagi sparsifolia SHAP. Seedlings to Different Irrigation Treatments

Seasonal variation of ecological properties of roots of Alhagi sparsifolia SHAP.seedlings under different irrigation treatments is studied by manual digging.Conclusions are as following:(1) In morphological features of roots: If water supply is relatively sufficient,the seedlings grow their horizontal roots and tiller new plants for getting more sunshine;if soil moisture content is limited,the seedlings grow their vertical roots in deeper soil.Such root growth is an important property of A.sparsifolia for adapting arid environment;(2) Root-shoot radio is increased with decreasing soil moisture content,especially at the late stage of growing season.To increase the root-shoot ratio is one of the properties of A.sparsifolia for adapting soil moisture shortage;(3) Growth depth and vertical growth speed of the seedling roots are increased with decreasing soil moisture content under the different irrigation treatments;(4) Biomass and surface area of roots are decreased with increasing soil depth,and they are in an inverse pyramid distribution.At the beginning of growth season,more biomass of A.sparsifolia increases in shoots for getting more sunshine,but at the end of growth season,much more biomass increases in roots for the growth next year.The formation process of biomass of roots accords with the Logistic S-shaped growth curve.Total biomass is decreased with increasing drought stress.