Improvement and Application of the Parameterization Scheme for Hydrothermal Properties of Rhizosphere Soil in Alpine Grassland

Plant roots signifificantly altered soil hydrothermal properties but was not typically included in land-surface process models. This omission affected the simulation results of soil water content and temperature, particularly on the Qinghai-Tibet Plateau (QTP) where roots in the shallow soil were generally high. Global grassland above-ground biomass carbon data and root distribution model were used to build a geographically distributed, profifiled alpine grassland roots density dataset for the Community Land Model (CLM). The schemes for soil hydrothermal properties were modified to accommodate soil mineral, organic matter and roots. Compared with the original schemes, the new schemes presented an increasing or decreasing trend. The new schemes were verified by single-point, regional offline simulation, and the influence of alpine grassland roots on simulation results on the QTP were explored. The new schemes could effectively block the downward migration of 0-10 cm soil water, which were beneficial to water conservation. The heat storage capacity of 0-10 cm soil increased obviously, and the thermal conductivity showed a certain seasonal change. Therefore, the simulated dry deviation of 0-10 cm soil water content in the new schemes was significantly reduced. The simulated 0-10 cm soil temperature in the new schemes during soil non-freezing was generally lower than the observed, and the simulated cold deviation of this layer during soil freezing was also reduced.