Discrepancy of sap flow in Salix matsudana grown under different soil textures in the water-wind erosion crisscross region on the Loess Plateau

An accurate understanding about the variation of sap flow and the interaction mechanisms of sap flow with environmental factors is essential when carrying out vegetation restoration projects in areas where rainfall is limited. A thermal dissipation probe (TDP) measured sap flow of Salix matsudana, growing in typical sandy and loess soils in the same semi-arid watershed on the Loess Plateau, China in 2012 and 2013 from May to October. Similar sap flow diurnal variation patterns occurred for both soils but, based on the sap flow, the calculated total transpiration of S. matsudana growing in the loess soil was about five times greater than that growing in the sandy soil due to differences in the sapwood cross-sectional area. Soil texture affected both the vertical distribution of S. matsudana fine roots and the soil water cycle, which led to the S. matsudana growing in the sandy soil being subjected more frequently to drought stress that stunted its growth. In contrast, S. matsudana grew well in the loess soil. Soil texture was the key factor responsible for the discrepancy in the total sap flow of S. matsudana in the study region due to its effect on soil water content. Therefore, if afforestation is planned for this or similar regions, soil texture should be taken into account.