Soil water threshold for the growth of Haloxylon ammodendron in the Ulan Buh desert in arid northwest China.

摘要

An experiment was conducted over a 3-year period to investigate the aeolian soil water dynamics and ecophysiological characteristics of Haloxylon ammodendron in Ulan Buh Desert, northwest China. Three different communities of H. ammodendron, which consist of two 8- to 10-year plantations and one natural stand, were selected in this study. As a result, the "economic water threshold" of H. ammodendron was expressed at about 2.0% of the absorbed water content. Above this threshold, the aeolian soil water potential decreased by -0.18 MPa with a 1.0% decrease in the water content. Below this threshold, the aeolian soil water potential decreased by -2.09 MPa with a 1.0% decrease in the water content. The predawn water potential of the shoot can recover to an above zero turgor pressure when the aeolian soil water content exceeded the "economic water threshold". However, the predawn water potential of the shoot became -3.50 MPa, which was lower than that at zero turgor (-3.41 MPa) when the aeolian soil water content was about 1.0%. This results indicated that the shoot cannot recover its turgor. Therefore, 1.0% of the aeolian soil water content was defined as the "survival water threshold" of the growth of H. ammodendron.