title: The Sap Flow Dynamics and Response of Hedysarum scoparium to Environmental Factors in Semiarid Northwestern China.
abstract: Hedysarum scoparium is an important, fast-growing and drought-resistant shrub that has been extensively used for grassland restoration and preventing desertification in semiarid regions of northwestern China. The primary objective of this study was to investigate the diurnal and seasonal variations in stem sap flow (Js) and its relation to environmental factors. The stem heat balance method was applied to plants that were approximately 17 years old (with diameters of 25, 16, 13, and 9 mm at ground level and heights of 3.1, 1.8, 1.7 and 1.4 m) and growing under natural conditions. The vertical soil temperature profile (ST), soil surface heat flux (SoilG), volumetric soil moisture content (SWC) and meteorological variables such as solar radiation (Rn), air temperature (Ta), vapour pressure deficit (VPD), wind speed (Ws) relative humidity (RH) and precipitation (P) were simultaneously measured at a meteorological station on site. Results indicated that Js varied regularly during the diurnal and seasonal term. The nocturnal Js was substantial, with a seasonal variation similar to the patterns of daytime Js. The magnitude of Js changed considerably between sunny and rainy days. Redundancy (RDA) and Kendall's tau analysis suggested that daily Js in large plants was more sensitive to environmental factors, and the variation in daily Js during the growing season could be described by a multiple linear regression against environmental variables including Ta, VPD, Ws, RH, ST, and SoilG. While the nocturnal Js in smaller plants was more sensitive to meteorological factors. Ta, VPD, and Ws were significantly correlated with nighttime Js. The hourly nighttime sap flow rate of H. scoparium corresponded closely to Ta and VPD following a non-linear pattern. The results of this study can be used to estimate the transpiration of H. scoparium.
authors.affiliation: Yanchi Research Station, School of Soil & Water Conservation, Beijing Forestry University, Beijing, 100083, P. R. China.
authors.forename: Jifeng
authors.initials: J
authors.lastname: Deng
authors.affiliation: Yanchi Research Station, School of Soil & Water Conservation, Beijing Forestry University, Beijing, 100083, P. R. China; Key Laboratory of Soil and Water Conservation and Desertification Combating, Ministry of Education, Beijing Forestry University, Beijing, 100083, P. R. China.
authors.forename: Guodong
authors.initials: G
authors.lastname: Ding
authors.affiliation: Yanchi Research Station, School of Soil & Water Conservation, Beijing Forestry University, Beijing, 100083, P. R. China; Key Laboratory of Soil and Water Conservation and Desertification Combating, Ministry of Education, Beijing Forestry University, Beijing, 100083, P. R. China.
authors.forename: Guanglei
authors.initials: G
authors.lastname: Gao
authors.affiliation: Yanchi Research Station, School of Soil & Water Conservation, Beijing Forestry University, Beijing, 100083, P. R. China; Key Laboratory of Soil and Water Conservation and Desertification Combating, Ministry of Education, Beijing Forestry University, Beijing, 100083, P. R. China.
authors.forename: Bin
authors.initials: B
authors.lastname: Wu
authors.affiliation: Yanchi Research Station, School of Soil & Water Conservation, Beijing Forestry University, Beijing, 100083, P. R. China; Key Laboratory of Soil and Water Conservation and Desertification Combating, Ministry of Education, Beijing Forestry University, Beijing, 100083, P. R. China.
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Yanchi Research Station, School of Soil & Water Conservation, Beijing Forestry University, Beijing, 100083, P. R. China; Key Laboratory of Soil and Water Conservation and Desertification Combating, Ministry of Education, Beijing Forestry University, Beijing, 100083, P. R. China.
authors.forename: Shugao
authors.initials: S
authors.lastname: Qin
authors.affiliation: Yanchi Research Station, School of Soil & Water Conservation, Beijing Forestry University, Beijing, 100083, P. R. China.
authors.forename: Wenhui
authors.initials: W
authors.lastname: Fan
mesh_terms: D002681:China; D017753:Ecosystem; D004777:Environment; D007887:Fabaceae / Q000502:physiology*; D065928:Forests; D005843:Geography; D006813:Humidity; D016014:Linear Models; D018515:Plant Leaves; D018547:Plant Stems / Q000502:physiology; D018526:Plant Transpiration / Q000502:physiology*; D011312:Pressure; D011891:Rain; D012044:Regression Analysis; D012621:Seasons; D012987:Soil; D013696:Temperature; D014197:Trees / Q000502:physiology*; D014919:Wind
chemical_list: D012987:Soil