Insect Herbivory Strongly Modifies Mountain Birch Volatile Emissions

Abstract

Insect herbivory is known to augment emissions of biogenic volatile organic compounds (BVOCs). Yet few studies have quantified BVOC responses to insect herbivory in natural populations in pan-Arctic regions. Here, we assess how quantitative and qualitative BVOC emissions change with increasing herbivore feeding intensity in the Subarctic mountain birch (Betula pubescens var pumila (L.)) forest. We conducted three field experiments in which we manipulated the larval density of geometrid moths (Operophtera brumata and Epirrita autumnata), on branches of mountain birch and measured BVOC emissions using the branch enclosure method and gas chromatography-mass spectrometry. Our study showed that herbivory significantly increased BVOC emissions from the branches damaged by larvae. BVOC emissions increased due to insect herbivory at relatively low larvae densities, causing up to 10% of leaf area loss. Insect herbivory also changed the blend composition of BVOCs, with damaged plants producing less intercorrelated BVOC blends than undamaged ones. Our results provide a quantitative understanding of the relationship between the severity of insect herbivore damage and emissions of BVOCs at larvae densities corresponding to background herbivory levels in the Subarctic mountain birch. The results have important and practical implications for modeling induced and constitutive BVOC emissions and their feedbacks to atmospheric chemistry.

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

“…Defoliating insects can also cause substantial damage to broadleaved plants. Feeding by the autumnal moth, Epirrita autumnata , has been shown to increase shoot BVOC emissions from mountain birch [ 31 , 100 , 101 ], silver birch [ 102 ], and hybrid aspen [ 103 , 104 ]. Shoot BVOC emissions were also found to increase in response to feeding damage by Erranis defoliaria in silver birch [ 50 ] and Cabera pusaria in alder ( Alnus glutinosa ) [ 105 ].…”

A New Field Instrument for Leaf Volatiles Reveals an Unexpected Vertical Profile of Isoprenoid Emission Capacities in a Tropical Forest

“…Forest-atmosphere interactions are shaped not only by the exchange of carbon, water, and energy, but also by the biological production of organic trace gasses (Laothawornkitkul et al, 2009;Unger, 2014;Rieksta et al, 2020;Tani and Mochizuki, 2021). For example, volatile isoprenoids (VI)-including 5C isoprene and a diversity of 10C monoterpenes-protect plants from diverse abiotic and biotic stresses (Fineschi et al, 2013), and contribute to the formation of atmospheric aerosols (Heald et al, 2008).…”

“…The first is an 'offline' approach, in which gas samples are collected in the field, and later analyzed in the lab. Typically, leaves are placed in flowthrough chambers such as commercial photosynthesis cuvettes or less quantitative enclosures, and gas samples are collected from the cuvette exhaust in bags or adsorption cartridges for later analysis by mass spectrometry (Tholl et al, 2006;Niinemets et al, 2010a;Alves et al, 2014;Jardine et al, 2020b;Rieksta et al, 2020). The advantages of this method include control of the leaf environment using a sophisticated leaf cuvette, precision quantification of emissions, and the ability to distinguish VI species.…”

A new field instrument for leaf volatiles reveals an unexpected vertical profile of isoprenoid emission capacities in a tropical forest

“…Forest-atmosphere interactions are shaped not only by the exchange of carbon, water, and energy, but also by the biological production of organic trace gases Rieksta et al, 2020;Tani & Mochizuki, 2021;Unger, 2014). For example, volatile isoprenoids (VI)-including 5C isoprene and a diversity of 10C monoterpenesprotect plants from diverse abiotic and biotic stresses (Fineschi et al, 2013), and contribute to the formation of atmospheric aerosols (Heald et al, 2008).…”

“…Typically, leaves are placed in flow-through chambers such as commercial photosynthesis cuvettes or less quantitative enclosures, and gas samples are collected from the cuvette exhaust in bags or adsorption cartridges for later analysis by mass spectrometry (Alves et al, 2014;K. J. Jardine, Zorzanelli, Gimenez, Robles, et al, 2020;Ülo Niinemets et al, 2010;Rieksta et al, 2020). The advantages of this method include control of the leaf environment using a sophisticated leaf cuvette, precision quantification of emissions, and the ability to distinguish VI species.…”