Comparison among Transpirations of Haloxylon ammodendron communities with Different Ages without Irrigation in the Gurbantonggut Desert

Through a field experiment conducted in the hinterland of the Gurbantonggut Desert,in this study,the dynamic water regime in the soil and its effects on the transpirations of 2～4-year-aged artificial mixed communities of Haloxylon ammodendron,spacing regularly at 2 m×1 m,are observed.The artificial communities are consisted of two dominant plant species,Haloxylon ammodendron and Calligonum caput-medusae,which were planted for one year in nursery before transplanted.The results are as follows:(1) The mean annual soil moisture content within 0～200 cm of soil layer under the communities decreases evidently with the increase of community age,figuring at 74.40 mm,66.08 mm,52.71 mm and 49.23 mm respectively in the bare area(controlled),two-year-aged,three-year-aged and four-year-aged communities;(2) In spring and early summer,there are no differences in transpirations of the 2～4-year-aged communities of Haloxylon ammodendron;in mid-summer,the transpiration of three-year-aged community of Haloxylon ammodendron is highest;in late summer and autumn,the transpirations of the communities of Haloxylon ammodendron decreases with the increase of their age;(3) As the community age goes up,the soil water stress to the growth of Haloxylon ammodendron is increased,and the growth of plants is delayed by the reduction of water consumption.For example,the mean annual water consumption of the 2～4-year-aged communities of Haloxylon ammodendron with average heights of 71 cm,132 cm and 75 cm and average canopy extents of 54 cm×57 cm,80 cm×123 cm and 58 cm×63 cm were 33 603.0 g,98 827.1 g and 32 231.5 g,respectively.In order to reduce the deficit of soil moisture supply and sustain the artificial mixed community,a suitable spacing between Haloxylon ammodendron and Calligonum caput-medusae should be selected.