Estimation of Water Consumption of Haloxylon ammodendron Sand-Fixing Forest in Minqin Oasis-Desert Ecotone of China Based on Leaf Index, China

In order to accurately estimate the water consumption of a Minqin desert Haloxylon ammodendron sand fixation forest, we used thermal equilibrium stem flow measurement to monitor the stem flow dynamics of Minqin desert H. ammodendron (5, 10, 15, and 20 years old, respectively, denoted as H5, H10, H15, and H20). In this study, we chose the growth index of assimilated branches (expressed as Ab in the following text) as the scalar quantity for expansion, and then estimated the water consumption of the H. ammodendron sand fixation forest by fitting the correlation between the water consumption of single H. ammodendron plants and the surface area and dry weight of single Ab. The results showed that the growth of assimilated H. ammodendron branches and the plant's monthly water consumption were synchronized, and that the growth of Ab and water consumption were significantly higher during the fast-growth period of H. ammodendron (July) compared to during the leaf-expanding (May) and leaf-falling periods (October). After correlation analysis, it was determined that there was a linear function between the surface area and dry weight of Ab and water consumption in H. ammodendron. The simulated water consumption values (kg) of H. ammodendron sand fixation forests were greatly affected by stand density and branching configuration, and the simulated values of H. ammodendron assimilated branch growth (cm) were slightly smaller than the measured values for forests of different ages, while the simulated values of assimilated branch surface area (cm2) had a much smaller relative error (8.92%) on average. Therefore, it is feasible to use the surface area and dry weight of Ab to calculate the water consumption of H. ammodendron sand fixation forests. This can enable the reliable estimation of the water consumption of H. ammodendron forests and provide a reference for desert vegetation sand fixation afforestation and its ecological water management.