Canopy transpiration of Pinus tabulaeformis plantation forest in the Loess Plateau region of China

Abstract

Transpiration is a significant hydrological process. Thus, the knowledge on the transpiration of Pinus tabulaeformis obtained from this study should be useful in water balance estimation and ecological vegetation construction and management. The variation in the sap flow of a mature P. tabulaeformis and the environmental conditions in the Anjiagou catchment located in the Loess Plateau of Northwest China during the growing season of 2014 were investigated. Based on the relative extractable water (θe), soil water conditions were classified into water stress (θe 0.425) conditions. Obvious differences were found between the responses of transpiration and its sensitivity to meteorological factors under the two different soil moisture conditions. During the entire growing season, the maximum and minimum daily stand transpiration (Es) rates were 2.18 and 1.39 mm day−1, with a mean Es of 1.83 mm day−1. The total Es from May to September was 277.68 mm. Es was linearly related to solar radiation but logarithmically related to vapor pressure deficit, variable of transpiration, and reference evapotranspiration under both soil moisture conditions. The sensitivity of Es to meteorological factors significantly decreased with increasing water stress conditions. These results not only provide a basis for the detailed analyses of water physiology and the growth of P. tabulaeformis plantations for the later application of a climate driven process model but also offer implications for forest management in the Loess Plateau of China.