The impact of beetle-induced conifer death on stand-scale canopy snow interception

Abstract

Bark beetles have killed more than 100,000 km2 of pine forest in western North America, causing trees to lose the majority of their canopy material and potentially leading to enhanced subcanopy snow accumulation. Over a 45-day period, we tested this hypothesis by measuring daily snow accumulation in three living and two dead lodgepole pine stands and in three adjacent clearings. The largest clearing was selected as our reference clearing based on previous studies. At maximum premelt snow water equivalent (SWE), this 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. Dead stand snowpacks were both denser and deeper than those in living stands. We attribute higher subcanopy accumulation under dead stands, compared to living stands, to diminished canopy snow interception and sublimation. Storm-scale canopy interception was also estimated by comparing SWE in forests and clearings before and after storm events. Over 10 storms, dead and living stands intercepted 18 and 41% of snowfall, respectively. The amount of interception increased linearly with storm size in the living stands, but not dead stands. We estimate more than half of snow falling on living stands sublimated, with measurably less sublimation in dead stands. © IWA Publishing 2013.