Herbivore-induced BVOC emissions of Scots pine under warming, elevated ozone and increased nitrogen availability in an open-field exposure

- Acantholyda posticalis triggers localized and systemic VOC emissions from Scots pine.
- Warming reduces herbivore-induced monoterpene emissions of Scots pine.
- Elevated ozone and nitrogen enhance monoterpene emissions increased by herbivory.
- Feeding damage by A. posticalis over a threshold causes emission burst of BVOCs.

Climate change may promote the frequency of insect attacks such as outbreaks of the great web-spinning pine sawfly (Acantholyda posticalis) on Scots pine (Pinus sylvestris L.). We determined the emission rates of localized biogenic volatile organic compounds (BVOCs) from A. posticalis-fed branches, and systemic BVOCs from non-fed branches of Scots pine seedlings defoliated for two growing seasons by A. posticalis larvae. Seedlings were also exposed to warming, elevated ozone and higher nitrogen availability for three years in an open-field experiment. A. posticalis feeding increased localized emissions of total non-oxygenated monoterpenes 21-fold, total oxygenated monoterpenes 9.1-fold, total sesquiterpenes 11-fold and total green leaf volatiles 9.2-fold from insect-damaged shoots on the 7th day of feeding in June. Warming reduced the effects of herbivory on the emission rates of total non-oxygenated monoterpenes by 77%. However, the effect of herbivory on total sesquiterpene emissions was enhanced by 16-fold in combination with warming and elevated ozone. The localized emission rates of total BVOCs were linearly increased when feeding damage intensity by larvae exceeded 80%. After three weeks of continuous sawfly feeding, herbivory stress increased systemic emissions of total non-oxygenated monoterpenes 5.6-fold, total sesquiterpenes 5.6-fold and total green leaf volatiles 6.5-fold from the non-damaged branch of larvae-fed seedlings, and this effect on total non-oxygenated monoterpene emission was enhanced 8.6-fold with elevated ozone. Herbivory sporadically showed post-feeding effects still by the end of 12th week from the initiation of feeding, increasing total non-oxygenated monoterpene emissions 4.4-fold at elevated nitrogen level. Our results suggest that Scots pine, at least in seedling stage, will be a stronger source of BVOC emissions in future due to expected increase of sawfly outbreaks with climate warming and by increased herbivory interactions with abiotic climate change factors.

116