Abstract
Compared to most other forest ecosystems, circumpolar boreal and subarctic forests have few tree species, and are prone to mass outbreaks of herbivorous insects. A short growing season with long days allows rapid plant growth, which will be stimulated by predicted warming of polar areas. Emissions of biogenic volatile organic compounds (BVOC) from soil and vegetation could be substantial on sunny and warm days and biotic stress may accelerate emission rates. In the atmosphere, BVOCs are involved in various gas-phase chemical reactions within and above forest canopies. Importantly, the oxidation of BVOCs leads to secondary organic aerosol (SOA) formation. SOA particles scatter and absorb solar radiation and grow to form cloud condensation nuclei (CCN) and participate in cloud formation. Through BVOC and moisture release and SOA formation and condensation processes, vegetation has the capacity to affect the abiotic environment at the ecosystem scale. Recent BVOC literature indicates that both temperature and herbivory have a major impact on BVOC emissions released by woody species. Boreal conifer forest is the largest terrestrial biome and could be one of the largest sources of biogenic mono- and sesquiterpene emissions due to the capacity of conifer trees to store terpene-rich resins in resin canals above and belowground. Elevated temperature promotes increased diffusion of BVOCs from resin stores. Moreover, insect damage can break resin canals in needles, bark, and xylem and cause distinctive bursts of BVOCs during outbreaks. In the subarctic, mountain birch forests have cyclic outbreaks of Geometrid moths. During outbreaks, trees are often completely defoliated leading to an absence of BVOC-emitting foliage. However, in the years following an outbreak there is extended shoot growth, a greater number of leaves, and greater density of glandular trichomes that store BVOCs. This can lead to a delayed chemical defense response resulting in the highest BVOC emission rates from subarctic forest in the 1–3 years after an insect outbreak. Climate change is expected to increase insect outbreaks at high latitudes due to warmer seasons and arrivals of invasive herbivore species. Increased BVOC emission will affect tropospheric ozone (O3) formation and O3 induced oxidation of BVOCs. Herbivore-induced BVOC emissions from deciduous and coniferous trees are also likely to increase the formation rate of SOA and further growth of the particles in the atmosphere. Field experiments measuring the BVOC emission rates, SOA formation rate and particle concentrations within and above the herbivore attacked forest stands are still urgently needed.
Highlights
Climate change effects on natural and man-made ecosystems are dominated by warming, which has resulted in global temperature increases of approximately 0.8 ◦C since the late 19th century
In this review we focus on the latest research on the emissions of non-methane biogenic volatile organic compounds (BVOC) from boreal and subarctic forest trees under a changing climate
While the BVOC emissions of aboveground plant parts have typically received greater attention than those emitted belowground, we found four studies addressing the effects of herbivore-feeding on BVOC emissions from the rhizosphere [10,13,43,50]
Summary
Climate change effects on natural and man-made ecosystems are dominated by warming, which has resulted in global temperature increases of approximately 0.8 ◦C since the late 19th century. The main drivers of rapid warming are increased ocean temperature that leads to decreased annual sea ice cover and reduced global albedo, and earlier terrestrial snow melt [2,3]. Climate change with warming and consequential changes in precipitation will result in the shift of vegetational zones toward the north These shifts include the expansion of woody shrubs into tundra ecosystems [20,21], a shift of the conifer boreal zone northwards to subarctic areas [18,22,23], and an increased proportion of deciduous trees within the boreal conifer forest [18,19]. This was not the case, but the total aerosol particle concentrations were elevated for up to a few years after the infestation, which was expected to indicate delayed defense responses, such as the stimulated regrowth of mountain birch [30]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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 call
