沙漠人工植被区的蒸发蒸腾

Evaporation and transpiration in re-vegetated desert area

研究于2003年6月至8月在沙坡头沙漠试验研究站的水分平衡观测场进行.利用微型蒸渗仪结合大型称重式土壤蒸渗仪测定了流沙、油蒿(Artemisia ordosica)和柠条(Caragana korshinskii)3类样地的土壤蒸发;油蒿和柠条的蒸腾利用表面覆盖油毡的大型非称重式蒸渗池和气孔计测定;同时对降水量、流沙渗漏量、0～200cm土层的土壤含水量进行了观测.结果表明:在沙漠人工植被区由于植被比较稀疏,土壤蒸发不受植株遮阴的影响,但不同样地的蒸发量是有差异的,样地和位置间的互作效应差异不显著;在沙漠区有很大比例的蒸发发生在稀少的降水事件之后.气孔计测定的蒸腾速率经单位换算统一,用多项式拟合得到日变化曲线均达到显著水平(p＜0.05);将蒸渗池和气孔计2种方法测定结果方差分析表明油蒿的蒸腾均高于柠条的(p＜0.05),测定方法间(蒸渗池和气孔计)差异不显著;从而说明本研究以叶面积指数和植物冠层盖度为基础进行叶片与种群间的尺度转换是可行的.2003年6月至8月期间,该区的降水量为159.1mm,渗漏量为48.5mm,裸沙蒸发量为63.0mm;油蒿样地的蒸发量、蒸腾量和蒸散量分别为54.1mm、59.0mm和119.4mm;柠条样地的蒸发量、蒸腾量和蒸散量分别为59.5mm、56.4mm和127.6mm.

The experiment was conducted on Water Balance Experimental Field （WBEF） in Shapotou Desert Research and Experiment station, through June to August 2003. The Shapotou of Ningxia Hui Autonomous Region, southeast edge of the Tengger Desert （37.32°N and 105.02°E） with an elevation of 1250m a. m. s. l. , is a steppe desert zone with an ecotone between desert and oasis . The annual mean precipitation is 186. 2mm and most of this falls between July and September. WBEF which was built in April of 1990 is consisted of Artemisia ordosica and Caragana korshinskii. Both of A. ordosica and C. korshinskii vegetation quadrats with 10m × 10m were plotted to investigate soil water content, evaporation and transpiration. Soil water contents were investigated by neutron probe, evaporation were determined by home-made micro-lysimeters, and transpirations were measured 4 times by LI-1600 stomas meter in experimental period. A weighting lysimeter with 2mz surface area in west of WBEF is used to measure evaporation and infiltration. To the north of lysimeter, 3 non-weighting lysimeters with size of 2m× 2m× 2m were covered by bitumen felt to determine transpiration and infiltration, two of which planted 4 A. ordosica and C. korshinskii, another is bare. The evaporation results determined by micro-lysimeters and lysimeter show that soil evaporation don＇t suffer to overshadow due to thin vegetation, but evaporation amount between A. ordosica and C. korshinskii vegetation is different, and the evaporations succedent rare precipitations in desert area are great. The transpiration rates determined by stomas meter were integrated to unit and simulated by polynomial, the results of diurnal variation curves of transpirations are all significant （p〈0. 05）. Through scale conversion, the transpirations of determined by non-weighting lysimeters and stomas meter are analyzed by ANOVA, the results show that the transpiration of A. ordosica is higher than that of C. korshinskii （p〈0. 05）, but the difference between methods is not significant. It indicates that the scale conversion between leaves level and population level based on canopy and leaves area index is feasible. From June to August in 2003, the precipitation, evaporation and infiltration of bare sand are 159. 1mm, 48.5mm and 63.0mm; The evaporation, transpiration and evapotranspiration in A. ordosica vegetation are 54. 1mm, 59.0mm and 119.4mm; The evaporation, transpiration and evapotranspiration in C. korshinskii vegetation are 59.5mm, 56.4mm and 127.6mm.