秋季巴丹吉林沙漠东南缘人工梭梭林水分来源

2009 年秋季( 9 月份) 在巴丹吉林沙漠东南缘的绿洲 - 荒漠过渡带,选择栽植 2,5,10,20 和 30 年的人工梭梭林,测定 20,30,50,100,150 和 200 cm 土深的土壤含水量,应用稳定氧同位素方法研究人工梭梭林的水分来源。结果表明: 梭梭林 20 ～ 30 cm 土层含水量显著高于 150 ～ 200 cm 土层; 土壤浅层的水分来自夏末和秋初的自然降雨; 随林龄增加,梭梭对地下水的利用比例逐渐增加,而对浅层土壤水分的利用比例逐渐降低; 2 年生梭梭依次主要利用 100,20,30,50 和 200 cm 土壤水分,5 年生梭梭依次主要利用地下水以及 200,150,100 和 30 cm 土壤水分,10 年生梭梭依次主要利用地下水以及 200,150,30 和 20 cm 土壤水分,20 年生梭梭依次主要利用地下水以及200 和 150 cm 土壤水分,而 30 年生梭梭依次主要利用 50,100,150,200,30 和 20 cm 土壤水分; 在巴丹吉林沙漠东南缘,随着林龄增加,梭梭对降雨补充的土壤浅层水分的利用能力降低,而对土壤深层水分与地下水的利用又不足以维持其正常生长需要,这可能是导致人工梭梭林大面积退化的一个原因。

Water Source of Haloxylon ammodendron Plantations in Autumn at the Southeast Edge of Badain Jaran Desert

Main water source of Haloxylon ammodendron was examined in six different ages (2, 5, 10, 20 ,and 30 years) of plantations in desert and the ecotone between oasis and desert at southeast edge of Badain Jaran Desert by the stable oxygen isotope technique in autumn (september) 2009. Meanwhile, soil water content was also measured in six different depths (20 cm, 30 cm, 50 cm, 100 cm, 150 cm and 200 cm). The results showed that soil water content in 20-30 cm was significantly higher than 150-200 cm in the all plantations. Soil water in shallow depths was supplied by natural rainfall in late summer and early autumn. With plantation age increased form 2-year-old to 20-year-old, H. ammodendron used more ratio of groundwater and less ratio of shallow layer soil water. Two-year-old H. ammodendron in turn mainly used 100 cm, 20 cm, 30 cm, 50 cm and 200 cm soil water; 5-year-old H. ammodendron in turn mainly used groundwater, 200 cm, 150 cm, 100 cm and 30 cm soil water; 10-year-old H. ammodendron in turn mainly used groundwater, 200 cm, 150 cm, 30 cm and 20 cm soil water; 20-year-old H. ammodendron in turn mainly used groundwater, 200 cm and 150 cm soil water; however, 30-year-old H. ammodendron in turn mainly used 50 cm, 100 cm, 150 cm, 200 cm, 30 cm and 20 cm soil water. At the southeast edge of Badain Jaran Desert, with the increase of plantation age, H. ammodendron had a declined capacity to make use of shallow soil water which is replenished by rainfall, whereas the utilization on deep soil water and ground water was not enough to meet its water requirement of growth. It might be a reason for the large area degradation of H. ammodendron plantations in the region.