荒漠地区主要固沙灌木的降水截留特征

在草原化荒漠带沙坡头地区,利用草方格沙障并栽植灌木柠条和半灌木油蒿对流动沙丘进行固定,经过40a的演变,逐渐形成由矮灌木与草本植物覆盖的固定沙丘景观.降水是该地区唯一的补给水源,对维持荒漠生态系统的稳定持续发展具有极其重要的作用.试验对两种主要固沙(半)灌木单株植物冠层在自然降水条件下的截留损失水量、冠层截留容量以及截留率与降水属性参数的关系进行了分析,并利用固沙植物群落内植被盖度等指标将所测得单株植物冠层截留转换为一定群落水平上冠层对降水的分割效应.结果表明,不同灌木类型的群落之间对降水截留的影响存在显著差别,对盖度达34%的油蒿群落而言,当单株植物投影面积平均为3900cm²时,其冠层截留容量约为0.7mm,群落截留损失水量平均占年降水量的26 8%;而盖度达30%的柠条群落,当单株植物投影面积平均为4070cm²时,其冠层截留容量约为0.3mm,群落截留损失水量平均占年降水量的17%.当降水强度<0.5mm·h^-1时,两种植物冠层截留水分与总降水量的比率随着降水强度的增加均呈明显的下降趋势;当降水强度>1mm·h^-1时,油蒿冠层截留与总降水量的比率基本稳定在0.3～0.4,柠条冠层截留与总降水量的比率基本稳定在0.2～0.3之间,比油蒿群落冠层截留率低10%左右.

Comparison of Interception Loss in Shrubby and Sub-shrubby Communities in the Tengger Desert of Northwest China

Forty years of re-vegetation, mainly by xerophytic shrubs Artemisia ordosica Krasch and Caragana korshinskii Kom, in the Shapotou Desert Experimental Research Station has established a dwarf-shrub and herbaceous cover on stabilized sand dunes. Precipitation, as the sole source of water replenishment in the semi-arid area, plays a pertinent role in sustaining the desert ecosystem. A field study was conducted to measure the interception loss by the shrubs canopy evaporation during individual rainfall events, and determine the rainfall-storage capacity of two plants canopy. The relationship between interception and rainfall parameters is discussed. The importance of vegetation cover can be seen in the distribution of rainfall and interception loss. Xerophyte shrub species could affect interception loss. For the Artemisia ordosica community with an average cover of 34 and the canopy projection of 39 cm×100 cm, the canopy storage capacity is 0.7 mm, and average interception loss is 26.82 of the total annual precipitation. In contrast, for the Caragana korshinskii community with an average cover of 30 and the canopy projection of 40.7 cm×100 cm, the canopy storage capacity is 0.3 mm, and average interception loss is 17 of the total annual precipitation. Both shrubby and sub-shrubby communities appear particular interception patterns, closely relating to the characteristics of rainfall during experimental periods. The proportion of interception loss to gross rainfall decreases with the rainfall intensity increasing when rainfall intensity is less than 0.5 mm·5h^-1. However, the proportion tends to remain constant at about 0.3～0.4 for Artemisia ordosica plant and 0.2～0.3 for Caragana korshinskii plant when the rainfall intensity is more than 1 mm·5h^-1.