Herbivore-Induced Monoterpene Emissions From Coniferous Forests: Potential Impact on Local Tropospheric Chemistry

Abstract

Herbivory results in an immediate increase in the rate of monoterpene emission from conifer tissues to the atmosphere. The current study uses simulated herbivory and a zero-dimensional photochemistry model with detailed treatment of monoterpene photooxidation to explore the potential impact of these herbivore-induced monoterpene emissions on local tropospheric chemistry dynamics. Measured monoterpene emission rates from undamaged current-year and year-old needles and wounded current-year needles of ponderosa pine and Douglas-fir trees were used to calculate whole-canopy fluxes expected from both a ponderosa pine and a Douglas-fir forest with 0%, 10%, and 25% damage to current-year needles. Fluxes from ponderosa pine forests with 10%-and 25%-damaged foliage are potentially 2-and 3.6-fold higher, respectively, than fluxes from forests with no herbivory. Douglas-fir forests experiencing 10% and 25% foliar damage can emit 1.6 and 2.5 times higher fluxes, respectively, than forests with no damaged foliage. The model simulations suggest that the fluxes resulting from even low-level herbivore damage (10% foliar damage) are large enough to increase local tropospheric production of ozone and organic nitrates and to suppress hydroxyl radical (OH) concentrations. In both Douglas-fir and ponderosa pine forests, the predicted magnitude of the perturbations to each of these chemical species increases linearly with the extent of foliar damage and is critically dependent on local mixing ratios of nitrogen oxides (NO x ). Ozone production is most sensitive to herbivore-induced emissions at NO x concentrations between 0.3 and 7 nmol/mol. The presence of isoprene in coniferous-forest air diminishes the role herbivory plays in generating local ozone production. The results suggest that defoliation events should be considered to represent an important potential control over local oxidative tropospheric chemistry and to play an important role in perturbing local ozone dynamics in many rural coniferous forests throughout the United States.

Impacts of Elevated Atmospheric CO2 and O3 on Forests: Phytochemistry, Trophic Interactions, and Ecosystem Dynamics

“…When BVOCs such as isoprene, monoterpenes or methylbutenol are oxidized in the presence of NO x , Litvak et al (1999) indicated that even modest (10%) damage by defoliating insects in coniferous forests is sufficient to increase local concentrations of O 3 . In contrast, in the presence of low NO x concentrations, BVOCs are oxidized by O 3 , leading to a decrease in atmospheric O 3 and a concomitant increase in secondary organic aerosols (Laothawornkitkul et al 2009).…”

Pine monoterpenes and pine bark beetles: a marriage of convenience for defense and chemical communication

“…Kesselmeier and Staudt (1999) estimate that the global carbon input for monoterpenes ranges between 127 and 480 Tg C year )1 . Monoterpene flux data for pines has been derived from (1) emissions measured around foliage (Litvak and Monson 1998;Litvak et al 1999;Niinemets et al 2002) or individual small trees (Tingley et al 1980;Juuti et al 1990;Shao et al 2001) and (2) measurements taken in or above the forest canopy (Schade et al 1999;Schade and Goldstein 2003;Holzinger et al 2005a;. The fluxes are increased by disturbances (Juuti et al 1990;Strö mvall and Petersson 1991;Schade and Goldstein 2003); by temperature (Tingey et al , 1991Juuti et al 1990;Charron et al 1995;Shao et al 2001); and by humidity (Schade et al 1999), leading to dynamic diurnal emission patterns (Schade and Goldstein 2003;Holzinger et al 2005b).…”

Differential controls by climate and physiology over the emission rates of biogenic volatile organic compounds from mature trees in a semi-arid pine forest

“…Once these compounds are emitted to the atmosphere, they participate in the chemistry that leads to the formation of tropospheric ozone and secondary organic aerosols and can have significant effects on regional 1 3 air quality (Litvak et al 1999;Monson 2002;Atkinson and Arey 2003;Park et al 2013) and climate (Goldstein et al 2009;Laothawornkitkul et al 2009;Ortega et al 2014). Numerous studies have been conducted on the responses of BVOC emissions to various biotic and abiotic stresses (Niinemets 2010).…”