The research of the response of sap flow in shrubs to rainfall pulses in the desert region of China was accomplished recently by the researchers of Cold and Arid Regions Environmental and Engineering Research Institute.The accomplishment of this research has the important significance to provide a scientific basis for understanding the mechanisms that underlie the responses of these desert plants to global climatic change.

Rainfall pulses can significantly drive the evolution of the structure and function of desert ecosystems,and understanding the mechanisms that underlie the response of desert plants to rainfall is the key to
understanding the responses of desert ecosystems to global climatic change. The present study was carried out at the desert-oasis ecotone in the middle of China’s Heihe River Basin. The researchers measured sap flow in the branches and stems of desert shrubs (Nitraria sphaerocarpa and Elaeagnus angustifolia) using sap flow gauges, and studied the response of sap velocity to rainfall pulses using the “threshold-delay” model. The results showed that the response of sap flow began about 1 h earlier after rainfall, and that sap velocity increased two to threefold, compared to its pre-rainfall value. The sap velocity increased significantly,then decreased gradually, with increasing rainfall. The response of sap flow differed significantly between rainfall, species, position within species during pulse duration, and the interactive effects also differed significantly (P < 0.0001). The response pattern followed the threshold-delay model, with lower thresholds of ≤5.2 and 1mmof rainfall for the stems and branches, respectively, demonstrating the importance of small rainfall events (<5mm) for plant growth and survival in desert regions.

This study was supported by the National Natural Science Foundation of China (No. 30771767) and the key project of the National Natural Science Foundation of China (No. 40930634).

(Installation of the sap flow gauges on the branches and stems of (A) N. sphaerocarpa and (B) E. angustifolia.)(image/Agricultural and Forest Meteorology)