Quantifying evapotranspiration and infiltration in a seasonally frozen forest

Abstract:

In seasonally frozen environments, hydrological processes are highly dynamic in the spring, during and following the melt period, and this is when most of the runoff and groundwater recharge happens. This is also when evapotranspiration fluxes start to increase in response to higher solar radiation, vegetation emergence and leaf-out. The impact of frozen soils on plant water uptake is still poorly understood. Previous studies have shown that evapotranspiration is over-estimated in the Canadian Land Surface Scheme (CLASS) during this period, at a sandy upland covered in Jack Pine, in the southern Canadian Boreal Forest. In this study we extend that work to look at three sites in the boreal forest in Saskatchewan; Old Jack Pine, Old Black Spruce and Old Aspen. These are Boreal Ecosystem Research and Monitoring sites (BERMs) which have been extensively and continuously monitored since the mid 1990s. The model will simulate the energy and water balance of the vegetation, soil and snowpack at the three sites. A multi-year meteorological dataset collected from the flux towers is used to force the model. We seek to critically examine infiltration and evapotranspiration at each site, using liquid soil moisture and above-canopy evapotranspiration observations derived from eddy covariance measurements.