Xin Zhiming, Feng Wei, Zhan Hongbin, Bai Xuying, Yang Wenbin, Cheng Yiben, Wu Xiuqin
School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China.
The Sand Forestry Experimental Center, Chinese Academy of Forestry, Hohhot 015200, China.
Plants (Basel). 2023 Jan 4;12(2):223. doi: 10.3390/plants12020223.
The ability of plants to absorb unsaturated atmospheric water vapor is a controversial topic. To study how vegetation in arid areas survives under limited water resources, this study uses Tamarisk in the Ulan Buh Desert of China as an example. The in-situ observation of a newly designed Lysimeter and sap flow meter system were used to monitor the precipitation infiltration and the utilization efficiency of Tamarisk of atmospheric vapor. The results show that the annual precipitation of 84 mm in arid areas could still result in deep soil recharge (DSR) with a recharge rate of 5 mm/year. Furthermore, DSR is detectable even in the winter, and the 5-year average DSR was 5.77% of the annual precipitation. It appears that the small precipitation events are critically important for the survival of Tamarisk. When the atmospheric relative humidity reaches 70%, Tamarisk leaves can absorb the unsaturated atmospheric vapor, which accounts for 13.2% of the annual precipitation amount. To adapt to the arid environment, Tamarisk can harvest its water supply from several sources including atmospheric vapor and micro-precipitation events (whose precipitation is below the measurement limit of 0.2 mm of the precipitation gauge) and can still permit a certain amount of recharge to replenish the deep soil moisture. Such an ecohydrological dynamic is of great significance to desert vegetation.
植物吸收不饱和大气水汽的能力是一个有争议的话题。为了研究干旱地区的植被在水资源有限的情况下如何生存，本研究以中国乌兰布和沙漠中的柽柳为例。利用新设计的蒸渗仪和液流计系统进行原位观测，以监测降水入渗和柽柳对大气水汽的利用效率。结果表明，干旱地区年降水量84毫米仍可导致深层土壤补给（DSR），补给速率为每年5毫米。此外，即使在冬季也能检测到深层土壤补给，5年平均深层土壤补给量占年降水量的5.77%。看来，小降水事件对柽柳的生存至关重要。当大气相对湿度达到70%时，柽柳叶可以吸收不饱和大气水汽，这占年降水量的13.2%。为了适应干旱环境，柽柳可以从包括大气水汽和微降水事件（其降水量低于雨量计0.2毫米的测量极限）在内的多种水源获取水分供应，并且仍能允许一定量的补给以补充深层土壤水分。这种生态水文动态对沙漠植被具有重要意义。
