Abstract
Abstract. Mountain pine beetle (MPB) outbreaks in North America are widespread and have potentially persistent impacts on forest albedo and associated radiative forcing. This study utilized multiple data sets, both current and historical, within lodgepole pine stands in the south-central Rocky Mountains to quantify the full radiative forcing impact of outbreak events for decades after outbreak (0–60 yr) and the role of outbreak severity in determining that impact. Change in annual albedo and radiative forcing peaked at 14–20 yr post-outbreak (0.06 ± 0.006 and −0.8 ± 0.1 W m−2, respectively) and recovered to pre-outbreak levels by 30–40 yr post-outbreak. Change in albedo was significant in all four seasons, but strongest in winter with the increased visibility of snow (radiative cooling of −1.6 ± 0.2 W m−2, −3.0 ± 0.4 W m−2, and −1.6 ± 0.2 W m−2 for 2–13, 14–20 and 20–30 yr post-outbreak, respectively). Change in winter albedo and radiative forcing also increased with outbreak severity (percent tree mortality). Persistence of albedo effects are seen as a function of the growth rate and species composition of surviving trees, and the establishment and growth of both understory herbaceous vegetation and tree species, all of which may vary with outbreak severity. The establishment and persistence of deciduous trees was found to increase the temporal persistence of albedo effects. MPB-induced changes to radiative forcing may have feedbacks for regional temperature and the hydrological cycle, which could impact future MPB outbreaks dynamics.
Highlights
Current outbreaks of bark beetles (Coleoptera: Curculionidae, Scolytinae) in western North America are some of the largest and most severe in recorded history (Bentz et al, 2009)
After mountain pine beetles (MPB) outbreak, an annual increase in Moderate Resolution Imaging Spectroradiometer (MODIS) albedo peaked at 14–20 yr with snag fall (0.06 ± 0.006) before transitioning to a minor, non-significant change in albedo (−0.01 ± 0.003 and 0.001 ± 0.003), relative to non-attacked stands, by 30–40 yr and 50–60 yr, respectively (Fig. 2)
The documented decrease in winter radiative forcing, due to increased snow visibility, could result in cooler wintertime air temperatures, potentially reducing beetle populations via winter “cold snaps” known to kill beetles. Both recent and historical, we quantified the cumulative radiative forcing due to MPB outbreaks in lodgepole pine stands in the south-central Rocky Mountains
Summary
Current outbreaks of bark beetles (Coleoptera: Curculionidae, Scolytinae) in western North America are some of the largest and most severe in recorded history (Bentz et al, 2009). Outbreaks result in tree mortality, temporarily reducing live tree density and changing stand reflectivity of shortwave radiation. Tree mortality has multiple stages, with the needles of a host lodgepole pine tree typically turning red within twelve months of being attacked (red attack stage) and falling off within three years (gray attack stage) (Mitchell and Preisler, 1998). In recent Colorado outbreaks (1996 to present), mountain pine beetles (MPB) (Dendroctonus ponderosae) have reduced the live basal area of lodgepole pine (Pinus contorta)-dominated forests by 70 %, on average (Klutsch et al, 2009). The current extent and high severity (percent tree mortality) of these recent MPB outbreaks has been attributed to warmer summer and winter temperatures and drought conditions associated with regional climate change (Berg et al, 2006; Raffa et al, 2008). Temperature and precipitation trends have increased over-winter survival of beetle populations, increased the rate of reproduction and maturation, and created drought-induced stress in tree hosts (Berg et al, 2006; Raffa et al, 2008)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
