The right-hand figure shows liquid water content as a function of temperature. This slows the temperature transition dramatically. It solves 1-D heat diffusion equation, with phase change and apparent heat capacity method. They drain if their water content is above a certain level. The mineral soil is assumed to drain at a 'unit hydraulic gradient,' that is, gravity drainage only.
Plant roots occur in litter, humus, and upper mineral layers.
Transpiration losses are determined by tree productivity and water-use efficiency. Most of the soil moisture dynamics is confined to the organic layers, particularly the moss layer. SNOW - Precipitation is partitioned into rain and snow by air temperature. Snowmelt is based on air temperature only. The snowpack can hold a certain amount of liquid water before draining.