Open AccessSensitivity of transpiration to subsurface properties: Exploration with a 1‐D model
Author(s) -
Vrettas Michail D.,
Fung Inez Y.
Publication year - 2017
Publication title -
journal of advances in modeling earth systems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.03
H-Index - 58
ISSN - 1942-2466
DOI - 10.1002/2016ms000901
Subject(s) - environmental science , evapotranspiration , transpiration , ecohydrology , hydraulic conductivity , infiltration (hvac) , moisture , dns root zone , precipitation , hydrology (agriculture) , dry season , soil science , mediterranean climate , water content , vegetation (pathology) , growing season , atmospheric sciences , soil water , ecosystem , geology , agronomy , ecology , meteorology , botany , photosynthesis , medicine , physics , geotechnical engineering , pathology , biology
The amount of moisture transpired by vegetation is critically tied to the moisture supply accessible to the root zone. In a Mediterranean climate, integrated evapotranspiration (ET) is typically greater in the dry summer when there is an uninterrupted period of high insolation. We present a 1‐D model to explore the subsurface factors that may sustain ET through the dry season. The model includes a stochastic parameterization of hydraulic conductivity, root water uptake efficiency, and hydraulic redistribution by plant roots. Model experiments vary the precipitation, the magnitude and seasonality of ET demand, as well as rooting profiles and rooting depths of the vegetation. The results show that the amount of subsurface moisture remaining at the end of the wet winter is determined by the competition among abundant precipitation input, fast infiltration, and winter ET demand. The weathered bedrock retains ∼ 30 % of the winter rain and provides a substantial moisture reservoir that may sustain ET of deep‐rooted (>8 m) trees through the dry season. A small negative feedback exists in the root zone, where the depletion of moisture by ET decreases hydraulic conductivity and enhances the retention of moisture. Hence, hydraulic redistribution by plant roots is impactful in a dry season, or with a less conductive subsurface. Suggestions for implementing the model in the CESM are discussed.