首页|Comparisons of three scaling up methods to estimate stand transpiration of a xerophytic shrub (Salix psammophila) in northern China
Comparisons of three scaling up methods to estimate stand transpiration of a xerophytic shrub (Salix psammophila) in northern China
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NSTL
Elsevier
Transpiration (T) is a key hydrological process, delivering water essential for plant metabolism and thus affecting productivity. A major challenge in estimating stand T is how to accurately scale sap flow data from individual trees to the stand. In shrub ecosystems, various scaling up methods have been used to extrapolate tree-level sap flow measurements to stand-level T, these include leaf area, cross-sectional area and number of branches. However, the performances of different scaling up methods have not been fully explored for shrubs. In this study, we measured sap flow of a xerophytic shrub (Salix psammophila) and scaled up using measures of leaf area, crosssectional area and numbers of branches in order to estimate stand T during the rainy seasons in 2019 and 2020 on the northern Loess Plateau, China. In addition, we measured precipitation, throughfall, stemflow, soil evaporation, surface runoff and 0-200 cm soil water content to calculate actual stand T on the basis of soil water balance method. The results revealed that daily stand T differed according to the scaling up methods used for the estimation. Daily estimated stand T based on measures of leaf area (0.1-13.1 mm d(-1)) was consistently higher than those based on cross-sectional area (0.2-8.6 mm d(-1)) and number of branches (0.4-8.9 mm d(-1)) (p < 0.05). During the two rainy seasons, the actual daily mean stand T (2.5 +/- 1.6 mm d(-1)) was significantly lower than the estimation by the three scaling up methods (p < 0.05). The method based on cross-sectional area appeared to be most suitable for scaling up because it had the lowest root mean square error and bias values (0.939 mm d-1 and 0.633 mm d(-1), respectively). This study highlights the wide variations of stand T upon which scaling up method was chosen, and these differences need to be considered when converting tree-level sap flow to stand-level T in shrub and other ecosystems.
Sap flowScaling upTranspirationShrubDrylandsHEAT-BALANCE METHODSOIL-WATER BUDGETSAP-FLOWEDDY COVARIANCEFOREST EVAPOTRANSPIRATIONSTOMATAL CONDUCTANCESAPWOOD AREAMASS-FLOWTREESFLUX
NSTL
Elsevier
