Variation of snow cover ablation in the boreal forest: A sensitivity study on the effects of conifer canopy

Abstract

Abstract. The duration and meteorological history of winter and thaw periods in the boreal forest affect carbon exchange during the growing season. Characteristics of conifer canopies exert important control on the energy exchange at the forest floor, which in turn controls snow cover processes such as melting. This analysis investigated the role of the conifer tree characteristics, including height and canopy density. Canopy and snow models estimated radiation incoming to the snow surface, the net energy budget of the snow, and melting rates of snow cover under conifer forests with different canopy density and tree height. This analysis assumed that canopy effects dominated snow surface energy exchange under conifers in the boreal forest. We used data layers of forest characteristics from the Boreal Ecosystem-Atmosphere Study (BOREAS) modeling subareas in Saskatchewan and Manitoba to guide the choice of modeled tree height and canopy density. Modeled stand characteristics assumed random location of trees and used a uniform tree height within a stand and regular crown geometry scaled to tree height. Measurements during winter and thaw in 1994 of incoming solar and longwave radiation, humidity, and wind speed above the forest canopy provided input to the models, along with air temperature measured in the canopy. Results showed the importance of canopy density and tree height as the firstorder controls on cumulative incoming solar radiation at the forest floor for the range of these variables in the BOREAS test area. The combined canopy and snow models showed a large range of snow ablation within conifers, which showed the trade-offs between canopy density and tree height. Solar fluxes dominated the net transfer of energy to the snow in the north, while sensible heat exchange, net solar, and net longwave radiation played important roles in the south.

Evaluation of the snow regime in dynamic vegetation land surface models using field measurements

“…By comparing adjacent forest and field sites, Zhang et al (2005) and Reba (2012) showed that snowpack sublimation is smaller in forests, mainly because of lower wind and net radiation, the latter of which is very sensitive to canopy characteristics (Davis et al, 1997). Furthermore, as Dery and Yau (2002) showed, the relative air humidity with respect to ice is lower in western Siberia than the east, so sublimation is likely to be higher in the western sector as it also dominated by field cover.…”

A Sensitivity Study of Daytime Net Radiation during Snowmelt to Forest Canopy and Atmospheric Conditions

“…Studies of the sensitivity of snowmelt to canopy coverage have generally been based on modeling results (Yamazaki and Kondo 1992;Davis et al 1997), as the difficulty of observing different snowmelt rates under various canopy covers is large. Suzuki and Ohta (2003) simulated snowmelt rates under larch forests of different densities.…”

Surface State across Scales; Temporal and Spatial Patterns in Land Surface Freeze/Thaw Dynamics

“…While tundra and lake-rich landscapes show a smaller variability in spring, forest landscapes show a smaller variability in autumn. The high variability of forest landscapes in spring could be attributed to snow melt, which is a heterogeneous process in forest-dominated landscapes [63]. Park et al [35] found different relationships for the spring transition date and the timing of snow melt for tundra and forest environments.…”