Potential of Climate Change and Herbivory to Affect the Release and Atmospheric Reactions of BVOCs from Boreal and Subarctic Forests

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.

Volatile-mediated between-plant communication in Scots pine and the effects of elevated ozone

“…In addition to facilitating trophic and multi-trophic interactions, HIPVs are involved in information transfer between plants, which is often referred to as plant–plant communication [ 10 ]. Stem feeding on conifers induces substantial VOC emissions [ 11 ], which provide potentially strong HIPV cues to other organisms in the community [ 12 ]. However, despite such HIPV-mediated between-plant communication being documented in numerous plant species [ 10 ], earlier studies have chiefly focused on herbaceous and broadleaved woody plants, with conifers largely unexplored.…”

Tree Communication: the Effects of “Wired” and “Wireless” Channels on Interactions with Herbivores

“…The release of the BVOCs is regulated by plant hormones, notably jasmonates, salicylic acid, and ethylene [50][51][52]. The sensitivity of BVOC emissions to biotic and abiotic stresses has been extensively reviewed [31,53,54]. Blends of HIPVs can be specific to a plant species and the herbivores feeding on it [51].…”

Tropospheric ozone and its natural precursors impacted by climatic changes in emission and dynamics

“…Temperature is an important factor controlling BVOC emissions (Fitzky et al, 2019;Yáñez-Serrano et al, 2020). Temperature changes directly affect the biochemical reactions in the metabolic pathways which produce BVOCs or have indirect effects like lengthening of the growing season (Peñuelas and Staudt, 2010;Yu et al, 2021). As temperatures increase, the enzymatic activities of synthesis are enhanced, BVOCs vapor pressure is increased and the resistance of the diffusion pathway is lowered.…”

“…Liu et al reported that since 2013 an increase in temperature and biogenic emissions led to a rise in the Maximum Daily Average 8-hourly (MDA8) O 3 mixing ratio by 1-2 ppbv (Liu and Wang, 2020). However, extreme temperatures and severe heat stress can cause cellular lesions and a drop in photosynthesis that may not improve upon return to cooler temperatures and reduce BVOCs emission (Yu et al, 2021).…”