增雨对巴丹吉林沙漠东南缘白刺水分利用的影响

Effects of increased precipitation on the water use of Nitraira tangutorum at southeast edge of Baddain Jaran Desert in China

研究了增雨条件下巴丹吉林沙漠东南缘的白刺灌丛的水分利用阈值.2009年5月初到9月末,根据当地的年均降水量(115mm),每月进行1次增雨,设置了0、50%和100%3个比例的增雨处理.在5、7和9月的增雨试验开始之前1天和增雨之后的第1、3和7天采样,测定白刺枝条木质部水分、10和30cm土层水分、灌溉井水和自然降雨的稳定氢同位素比率,以及土壤含水量的变化.结果表明:自然条件下,白刺在5和9月主要利用地下水,7月主要利用土壤浅层10和30cm水分.增雨后,白刺对地下水的利用比例下降,对浅层土壤水分的利用比例增加.100%增雨对白刺枝条木质部水分的δD值影响显著,5、7和9月白刺的水分利用比例增加.而50%增雨在5和7月仅改善了土壤水分条件,白刺的水分利用比例没有明显增加.只有增雨量达到当地年均降水量时,白刺对水分的利用比例才能明显增加.

This paper studied the threshold value of the water use of Nitraria tanturorum shrubs at the southeast edge of Baddain Jiran Desert. From the early May to late September in 2009, an irrigation simulating increased precipitation was conducted once every month. Three ratios of increased precipitation （0, 50% and 100% ） were designed, based on the local mean annual precipitation （ 115 mm）. On the 1 day before irrigation and the 1,3 and 7 days after irrigation in May, July and September, the c^D in the xylem water of N. tangutorum, the soil water at the depths 10 and 30 cm, and the well water and natural rainfall, and the variations of the soil water content were measured. Under natural condition, the N. tangutorum mainly utilize ground water in May and September, and utilize the soil water at the depths 10 and 30 cm in July. After irrigation, the ground water use rate of the N. tangutorum decreased, while the soil water use rate increased. In the treatment of 100% increased precipitation, the δD ratio of the water in N. tangutorum xylem was affected sig- nificantly, and the water use of the N. tangutorum in May, July and September increased. In the treatment of 50% increased precipitation, the soil water condition in May and July was improved, but the water use rate had little improvement. Only when the increased precipitation reached 100% of the local mean annual precipitation, could the water use rate of the N. tangutorum have an obvious increase.