The impact of bark beetle infestations on monoterpene emissions and secondary organic aerosol formation in western North America

Abstract

Over the last decade, extensive beetle outbreaks in western North America have destroyed over 100 000 km² of forest throughout British Columbia and the western United States. Beetle infestations impact monoterpene emissions through both decreased emissions as trees are killed (mortality effect) and increased emissions in trees under attack (attack effect). We use 14 yr of beetle-induced tree mortality data together with beetle-induced monoterpene emission data in the National Center for Atmospheric Research (NCAR) Community Earth System Model (CESM) to investigate the impact of beetle-induced tree mortality and attack on monoterpene emissions and secondary organic aerosol (SOA) formation in western North America. <br><br> Regionally, beetle infestations may have a significant impact on monoterpene emissions and SOA concentrations, with up to a 4-fold increase in monoterpene emissions and up to a 40% increase in SOA concentrations in some years (in a scenario where the attack effect is based on observed lodgepole pine response). Responses to beetle attack depend on the extent of previous mortality and the number of trees under attack in a given year, which can vary greatly over space and time. Simulated enhancements peak in 2004 (British Columbia) and 2008 (US). Responses to beetle attack are shown to be substantially larger (up to a 3-fold localized increase in summertime SOA concentrations) in a scenario based on bark-beetle attack in spruce trees. Placed in the context of observations from the IMPROVE network, the changes in SOA concentrations due to beetle attack are in most cases small compared to the large annual and interannual variability in total organic aerosol which is driven by wildfire activity in western North America. This indicates that most beetle-induced SOA changes are not likely detectable in current observation networks; however, these changes may impede efforts to achieve natural visibility conditions in the national parks and wilderness areas of the western United States

Impacts of simulated herbivory on volatile organic compound emission profiles from coniferous plants

“…This stressor increases OVOC emissions in the short-term, but after prolonged exposure to the stressor, plants close their stomata to conserve water and a resulting drop in OVOC emissions occurs (Filella et al, 2007;Graus et al, 2013). This same threshold effect was not observed for terpene foliar concentrations and terpene emissions from Mediterranean tree species and C4 crops (Blanch et al, 2009;Graus et al, 2013). However, other studies have demonstrated that under severe enough drought stress, monoterpene emissions also begin to decrease (Ormeno et al, 2007;Simpraga et al, 2011).…”

“…It is well established that herbivory can increase monoterpene, sesquiterpene, and small OVOC emission rates and substantially alter the BVOC profile (Achotegui-Castells et al, 2013;Hu et al, 2008;Laothawornkitkul et al, 2008;Semiz et al, 2012). The presence of herbivore infestation can increase BVOC emissions by 4-to 20-fold (Amin et al, 2012(Amin et al, , 2013Berg et al, 2013), and this response can last for several weeks (Priemé et al, 2000). These results suggest that herbivore stress could have a substantial impact on SOA formation in forest environments in the future.…”

Simulating secondary organic aerosol from missing diesel-related intermediate-volatility organic compound emissions during the Clean Air for London (ClearfLo) campaign

“…In some cases, this underestimation has been shown to be due to problems with the underlying emission inventories, particularly for domestic wood burning in wintertime (Simpson et al, 2007;Denier van der Gon et al, 2015). There may also be sources of biogenic secondary organic aerosol (BSOA) arising from previously neglected VOC emissions such as those induced by biotic stress (Berg et al, 2013;Bergström et al, 2014).…”

The impact of historical land use change from 1850 to 2000 on secondary particulate matter and ozone

“…Tree mortality, for example associated with insect infestation or disease, can modulate biosphere-atmosphere exchange, generating transitory perturbations in air quality (Berg et al, 2013;Geddes et al, 2016). However, conversion of land cover, for example via clearing, can lead to longterm changes in surface properties and therefore atmospheric composition.…”