半干旱区湿地地下水埋深对芦苇SPAC系统水分运移耗散的影响

准确把握土壤-植被-大气系统（简称"SPAC"）中水分的运输和耗散规律是区域水资源可持续管理的重要前提。以白洋淀湿地为研究区，结合现场实测和模型模拟方法，探讨台田地下水埋深变化对芦苇SPAC系统中的水分运移耗散影响。结果表明:1）随着地下水埋深的增加，芦苇蒸散发（ET_a）开始下降，ET_a下降的地下水埋深阈值在100 cm左右；随着地下水埋深的降低，生长季0~120 cm土壤剖面由水分亏损转为盈余，亏盈转换的地下水埋深阈值在60 cm左右，并且亏损量与地下水埋深呈正相关。2）相同的地下水埋深变化对不同月的土壤水分储量、蒸散发的影响程度均存在差异，其中6月影响程度最高。在对白洋淀进行生态补水时，应避免在汛期前的春季进行大量的生态补水，可以优先考虑在生长末期的秋冬季来进行生态补水。3）综合考虑植被生长需求和生态节水，白洋淀芦苇最优的地下水埋深区间在110~150 cm，此时生长季内芦苇蒸散发具有10%~20%的节水潜力。

INFLUENCES OF GROUNDWATER DEPTH ON WATER TRANSPORT AND DISSIPATION IN SPAC SYSTEM OF PHRAGMITES AUSTRALIS IN A SEMI-ARID WETLAND

It was an important premise for sustainable management of regional water resources to accurately grasp the law of water transport and dissipation in the soil-plant-atmosphere continuum (SPAC). In this paper, the Baiyangdian wetland was taken as the research area. Combined with field measurement and model simulation method, influences of groundwater depth change on the water transport and dissipation in the SPAC system of Phragmites australis were discussed. The main conclusions of this study was as follows:1) Evapotranspiration of Phragmites australis (ET_a) decreased with the increase of groundwater depth, and the threshold of groundwater depth for ET_a to decrease was about 100 cm. With the decrease of groundwater depth, the soil profile balance during the whole growing season changed from water deficit to surplus. The groundwater burial depth threshold value that soil profile balance changed from water deficit to surplus was 60 cm, and the deficit amount was positively related to groundwater burial depth. 2) The effect levels of groundwater depth change on soil water storage and evapotranspiration in different months were different, and they reached peak in June. A large amount of ecological water replenishment should be avoided in spring and before the flood season, and the recommended water replenishment timings was autumn and winter. 3) With a comprehensive consideration of vegetation growth demand and water conservation, the optimal groundwater depth range of Phragmites australis communities was 110~150 cm in Baiyangdian wetland. Under the optimal scenario, the evapotranspiration of Phragmites australis communities in the growing season had 10%~20% water-saving potential.