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Pugh, Evan T ¹ ; Small, Eric E ²

¹ University of Colorado
² University of Colorado

In western North America, the mountain pine beetle has killed more than 100,000 km² of lodgepole pine (Pinus contorta) forest, causing trees to lose the majority of their canopy material. We hypothesize that tree death significantly reduces available interception platforms, leading to greater subcanopy snow accumulation than pre-infestation conditions. Over a 45-day period, we measured daily snow accumulation in three living and two dead lodgepole pine stands and in three adjacent clearings. The largest of these clearings was selected as our reference clearing based on previous studies. At maximum pre-melt snow water equivalent (SWE), the reference clearing had accumulated 50.4 cm SWE, while 45.6 cm SWE accumulated under dead stands and 38.1 cm SWE accumulated under living stands. We attribute this higher subcanopy accumulation under dead stands versus living stands to diminished canopy snow interception and sublimation. Storm-scale canopy interception was also estimated. We compared SWE in forests and clearings before and after storm events. Dead and living stands accumulated 92% and 80% as much SWE as the reference clearing, respectively. Based on a comparison of season- and storm-scale subcanopy snow accumulation, we estimate 72% sublimation losses for incoming snowfall in living stands compared to 46% for dead stands. Finally, we identify potential reasons that dead stands intercept less snow and suggest specific changes that can be implemented to improve interception modeling.