Net precipitation in burned and unburned subalpine forest stands after wildfire in the northern Rocky Mountains

Abstract

Wildfire can exert considerable influence on many watershed processes, including the partitioning of precipitation by forest canopies. Despite general acknowledgement that canopy interception is reduced following wildfire, effects on net rainfall and snow accumulation have not been quantified. The objectives of this study were to document net rainfall and snow water equivalent (SWE) in burned and unburned (reference) forest stands over a 10-year period to characterise the effects of severe wildfire on net precipitation in the Canadian Rocky Mountains. Differences in summer (June–September) rainfall between burned and reference stands suggest that wildfire reduced rainfall interception by 65%, resulting in a 48% increase in net rainfall from 2006 to 2008. This represented an average annual increase in net rainfall of 122mm (36%) for 10 years after the fire. Similarly, a burned stand had 152mm (78%) higher mean annual peak SWE than a paired reference stand. Collectively, burned stands had 274mm (191–344mm; 51%) more mean annual net precipitation for the first decade after fire. These results suggest that increases in net precipitation are likely following wildfire in subalpine forests and that, owing to the slow growth of these forests, post-fire changes may alter precipitation–runoff relationships for many years.

Hillslope and groundwater contributions to streamflow in a Rocky Mountain watershed underlain by glacial till and fractured sedimentary bedrock

“…A total of five, four, and three samples were collected throughout the summers of 2013, 2014, and 2015, respectively. The difficulty in capturing large convective storms and the large frequency of storms of less than 5 mm (Williams et al, 2019) prevented the collection of more rainfall samples.…”

“…Forest disturbance from wildfire, pathogens, or forest harvesting removes the forest canopy, increasing the total precipitation that reaches the forest floor (Williams et al, 2019;Burles and Boon, 2011;Boon, 2012;Pugh and Small, 2012;Varhola et al, 2010), often altering the dominant flow pathways, increasing streamflow quantity, and changing the timing of flows in forested watersheds (Stednick, 1996;Scott, 1993;Bearup et al, 2014;Winkler et al, 2017). However, large variability has been observed in streamflow responses following disturbance due to differences in disturbance type, vegetation type, precipitation regimes, and soil moisture storage (Brown et al, 2005;Stednick, 1996).…”

Seasonally varied hillslope and groundwater contributions to streamflow in a glacial till and fractured sedimentary bedrock dominated Rocky Mountain watershed

“…Five, four, and three samples were collected throughout the summers of 2013, 2014, and 2015, respectively. The difficulty of capturing large convective storms and the large frequency of storms less than 5 mm (Williams et al, 2019) prevented the collection of more rainfall samples.…”

“…Forest disturbance from wildfire, pine beetle infestation, or forest harvesting removes the forest canopy increasing the total precipitation that reaches the forest floor (Williams et al, 2019;Burles and Boon, 2011;Boon, 2012;Varhola et al, 2010) 30 often altering the dominant flow pathways, increasing streamflow quantity and changing the timing of flows in forested watersheds (Stednick, 1996;Scott, 1993;Winkler et al, 2017). However, large variability has been observed in streamflow responses following disturbance due to differences in disturbance type, vegetation type, precipitation regimes, and soil moisture storage (Brown et al, 2005;Stednick, 1996).…”

Snowpack properties vary in response to burn severity gradients in montane forests

“…Snow-water resources from mountain watersheds provide fresh water for over 1/5 of the global human population and are critical for the function of montane ecosystems (Barnett et al 2005). Snowpack accumulation and ablation in mountain watersheds has shown to be strongly influenced by forest composition and structure (Veatch et al 2009, Varhola et al 2010, Hubbart et al 2015, Williams et al 2019. Forest cover can reduce snowpack by intercepting falling snow on branches and making it more vulnerable to loss through sublimation, yet, forest cover can also increase snowpack by protecting it from incoming solar radiation and other turbulent fluxes once snowfall has reached the forest floor (Musselman et al 2008.…”