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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.
We studied the threshold of water use efficiency of Nitraria tangutorum in the southeastern margin of Badain Jaran Desert under increasing rainfall conditions.At the beginning of May to the end of September 2009, rainfall was increased once a month according to the annual average precipitation (115mm) 0, 50%, and 100% of rainfall.The sampling was done on the 1st, the 1st, the 7th and the 7th days after the rainy days of May, July and September, , 10 and 30 cm soil layers, stable hydrogen isotope ratio of well and natural rainfall, and changes of soil water content.The results showed that groundwater was mainly used by white thorn in May and September and July mainly by soil Shallow 10 and 30 cm of water.After the rain, the proportion of white thorns to groundwater decreased, and the proportion of shallow soil water increased.The 100% increase of rainfall had significant effect on the δD value of xylem water, and 5, 7 and 9 The percentage of water use of Nitraria tangutorum increased, while that of 50% increase only improved the soil moisture condition in July and July, and the proportion of water use of Nitraria tangutorum did not increase significantly.While the increase of precipitation reached the local average annual precipitation, The proportion of water use can be significantly increased.