干旱荒漠区绿洲边缘典型固沙灌木的降水截留特征

在民勤绿洲边缘,降水对维持固沙灌木持续稳定发挥固沙功能具有重要作用。本文选择民勤绿洲边缘3种主要固沙灌木为研究对象,观测了降雨条件下降水穿透量和冠层截留量,分析了降水穿透量和冠层截留量与降雨量之间的关系以及截留率与降水强度之间的关系,比较了不同灌木群落的降水截留特征。结果表明,不同灌木的降水截留存在明显差异,梭梭、柽柳、生长良好白刺、衰退白刺冠层最大截留量和截留容量分别为0.6 mm、0.6 mm、0.4 mm、0.3 mm和0.8 mm、0.8 mm、0.5 mm、0.2 mm；在两年总降水量255.3 mm条件下,梭梭、柽柳和生长良好白刺3种灌木群落冠层截留损失分别为44 mm、88 mm和32 mm,占降水总量的16.6%、33.1%和12.0%；当降雨强度<0.8 mm·h-1,梭梭和柽柳降水截留率随降水强度增加均呈递减趋势；当降水强度>0.8 mm·h-1时,梭梭冠层截留量与降水量的比率基本稳定在0.2～0.3之间,柽柳在0.3～0.4之间；当降水强度<0.5 mm·h-1,生长良好白刺灌丛的降水截留率随降水强度增加呈下降趋势；当降雨强度>0.5 mm·h-1,生长良好白刺灌丛截留率基本维持在0.1～0.2之间；降雨强度>0.4 mm·h-1时,衰退白刺截留率稳定在0.05～0.1之间。

The Interception Loss of Rainfall by Three Sand-fixing Shrubs at the Fringe of Minqin Oasis

Precipitation plays an important role for the growth and sand fixing of fixing-sand shrubs in Minqin oasis fringe. A field observation was conducted to measure precipitation permeating canopies of three shrubs and the precipitation interception loss by canopies of the three shrubs during different rainfall events, and relationships between precipitation permeating canopies of three shrubs and precipitation, the precipitation interception loss by canopies of the three shrubs and precipitation, and precipitation interception ratio and precipitation intensity were analyzed, and the different influences of the three shrubs on canopy precipitation interception loss were compared. The results showed that, the interception loss in the canopies among the three shrubs had significant differences during individual rainfall events; the maximum interception loss for the canopies of Haloxylon ammodendron, Tamarix ramosissima, normal Nitraria tangutorum and degraded N. tangutorum were 0.6 mm, 0.6 mm, 0.4 mm, 0.3 mm, respectively; while the maximum interception capacity were 0.8 mm, 0.8 mm 0.5 mm, 0.2 mm, respectively; the estimated total canopy interception losses for the communities of the three shrubs were 44 mm, 88 mm and 32 mm, respectively, which were 16.6%, 33.1% and 12.0% of the total 255.3 mm rainfall during the two years, respectively; the proportion of interception loss to gross rainfall for H. ammodendron and T. ramosissima decreased with the rainfall intensity when rainfall intensity was less than 0.8 mm·h-1, and tended to remain constant at 0.2-0.3 for H. ammodendron and 0.3-0.4 for T. ramosissima when the rainfall intensity was more than 0.8 mm·h-1; the proportion of interception loss to gross rainfall decreased with the rainfall intensity if rainfall intensity was less than 0.5 mm·h-1, and tended to keep constant at about 0.1-0.2 for the normal N. tangutorum when the rainfall intensity was over 0.5 mm·h-1; the constant interception proportion for the degraded N. tangutorum was  0.05-0.1 for when the rainfall intensity was more than 0.4 mm·h-1.