高寒沙区生物土壤结皮对吸湿凝结水的影响

Effects of biological soil crusts on the characteristics of hygroscopic and condensate water deposition in alpine sandy lands

高寒沙区,水资源匮乏,吸湿凝结水是维持当地生态环境的重要非生物影响因子。采用自制微渗仪(直径10 cm,高度分别为3、4、6、11 cm)观测3类生物土壤结皮(苔藓结皮、藻类结皮、物理结皮)和流沙的吸湿凝结水量变化规律。结果表明:观测期间,除去大风和降雨天气外,吸湿凝结水每天都会产生;不同地表类型产生的吸湿凝结水量存在差异,生物土壤结皮生成的吸湿凝结水量显著大于流沙上产生的吸湿凝结水(P<0.05),即生物土壤结皮有利于吸湿凝结水的生成;随着结皮的发育,吸湿凝结水量呈增加趋势,主要表现为:流沙<物理结皮<藻类结皮<苔藓结皮;凝结现象自19:00开始,次日7:00结束;日出后,吸湿凝结水量迅速下降,持续时间为5 h,其中苔藓结皮与流沙下降速率最快;吸湿凝结水主要集中在土壤表层5 cm内,达总凝结量的90%以上,且观测值变异系数小,可作为代表性土壤深度进行吸湿凝结水的相关研究;吸湿凝结水量与大气温湿度密切相关,与大气温度呈负相关关系,与大气湿度呈正相关关系;吸湿凝结水量受取样深度、地表类型、大气温湿度等多方面因素的影响。

Water resource is scarce in alpine sandy areas. Hygroscopic and condensate water is an important abiotic factor in the maintenance of the local ecological environment. In this research, we used micro-lysimeters which has 10 cm in diameter and 3, 4, 6 cm in height to measure the variations of the hygroscopic and condensate water content in three types of biological soil crusts （moss, algae, and physical crusts） and moving sand. The results indicated that hygroscopic and condensate water generated almost every day except the windy and rainy days; contents of hygroscopic and condensate water at different land cover types were significant different, and the contents of hygroscopic and condensate water in biological soil crusts were higher than that in moving sand which indicating that biological soil crusts are conducive for the formation of hygroscopic and condensate water. There was an increasing trend of hygroscopic and condensate water content with the development of soil crusts：sand 〈 physical crusts 〈 algae crusts 〈 moss crusts. Hygroscopic and condensate water content occurred from 7：00 pm to 7：00 am in the next day. After sunrise, hygroscopic and condensate water content decreased rapidly within 5 hours. The fastest rate of decrease was found in moss crusts and sand. More than 90% of hygroscopic and condensate water presented in the top of soil within 5 cm which could be used as representative soil depth for further study of hygroscopic and condensate water for low variable coefficient; the contents of hygroscopic and condensate water was negatively correlated with atmospheric temperature and positively correlated with humidity; the hygroscopic and condensate water content was mainly affected by the factors such as sampling depth, surface type, atmospheric temperature, and humidity.