Dynamics of water use efficiency of Artemisia ordosica leaf in growing season in response to environmental factors in Yanchi, Ningxia of northwestern China

  Objective  We aimed to understand the seasonal dynamics of leaf water use efficiency and its response to environmental factors in Artemisia ordosica, a typical sandy plant in the semi-arid ecosystem of northwestern China for the purpose of ecosystem process modeling.

  Method  The leaf stomatal conductance (g_s), net photosynthetic rate (P_n) and transpiration (E) of Artemisia ordosica were measured using Li-6 400 portable photosynthetic analyzer from May to September, 2018. Water use efficiency (WUE, WUE = P_n / E) was analyzed in relation to soil water content (SWC), saturated water vapor pressure deficit (VPD₁), photosynthetically active radiation (PAR) and leaf surface temperature (T_l).

  Result  The g_s, P_n, E and WUE were more sensitive to VPD₁ when SWC ≤ 0.08 m³/m³. When SWC > 0.08 m³/m³, the g_s, P_n, E and WUE were more sensitive to the response of PAR and T_l.

  Conclusion  The results of this study further prove that Artemisia ordosica acclimates to drought conditions through changing g_s and relative magnitude of P_n and E, and thus changing WUE. And WUE is lower during drought, indicating that soil drought stress restricts leaf photosynthesis and WUE. It is concluded that Artemisia ordosica acclimats to dry environmental conditions through conservative strategy of water resource.