Study on the Dynamics of Stem Sap Flow in Minqin Wind and Sand Control Haloxylon ammodendron Forest, China

In this study, we obtained real-time data on the stem fluid flow of Haloxylon ammodendron in the growing season in Minqin, China, based on thermal diffusion (TDP) monitoring technology, and analyzed the dynamic changes of stem fluid flow in it to provide important supporting evidence for understanding the water consumption of H. ammodendron during its growth. The results indicate that the fluid flow in the stem of the H. ammodendron increases with increasing growth age and also decreases as the H. ammodendron grows older and declines. The average daily sap flow rates of H. ammodendron stems were 0.956, 1.059, 1.460 and 0.570 cm3·(cm2·h)−1 at 5, 10, 15 and 20 years, respectively, and the cumulative sap flow masses during the growing season from May to October were 610.173, 423.386, 1041.186 and 430.212 kg, respectively. H. ammodendron stem sap flow increases with the thickening of H. ammodendron’s ground diameter. The average daily sap flow rate of H. ammodendron stems at different stem levels ranged from 0.276 to 2.132 cm3·(cm2·h)−1, and the cumulative sap flow mass during the growing season ranged from 121.656 to 1722.810 kg. The larger the diameter of the H. ammodendron at different forest ages, the earlier the sap flow initiation time and the higher the peak. The stem flow initiation time was 7:00–8:00, and the average daily maximum fluid flow rate was 2.493–5.536 cm3·(cm2·h)−1, with the peak occurrence time advancing with age. The sap flow variation of H. ammodendron at different stand ages reflects the water-consuming process of H. ammodendron growth and its response to a drought environment, while the sap flow variation of H. ammodendron at different diameter classes shows that the individual growth differences of H. ammodendron also yield obvious competitive advantages. The results of the analysis can provide theoretical support for the estimation of ecological water use in desert H. ammodendron sand-fixing forests.