Volatile and Within-Needle Terpene Changes to Douglas-fir Trees Associated With Douglas-fir Beetle (Coleoptera: Curculionidae) Attack

Abstract

Mass attack by tree-killing bark beetles (Curculionidae: Scolytinae) brings about large chemical changes in host trees that can have important ecological consequences. For example, mountain pine beetle (Dendroctonus ponderosae Hopkins) attack increases emission of terpenes by lodgepole pine (Pinus contorta Dougl. ex Loud.), affecting foliage flammability with consequences for wildfires. In this study, we measured chemical changes to Douglas-fir (Pseudotsuga menziesii var. glauca (Mirb.) Franco) foliage in response to attack by Douglas-fir beetles (Dendroctonus pseudotsugae Hopkins) as trees die and crowns transitioned from green/healthy, to green-infested (year of attack), to yellow (year after attack), and red (2 yr after attack). We found large differences in volatile and within-needle terpene concentrations among crown classes and variation across a growing season. In general, emissions and concentrations of total and individual terpenes were greater for yellow and red needles than green needles. Douglas-fir beetle attack increased emissions and concentrations of terpene compounds linked to increased tree flammability in other conifer species and compounds known to attract beetles (e.g., [Formula: see text]-pinene, camphene, and D-limonene). There was little relationship between air temperature or within-needle concentrations of terpenes and emission of terpenes, suggesting that passive emission of terpenes (e.g., from dead foliage) does not fully explain changes in volatile emissions. The potential physiological causes and ecological consequences of these bark beetle-associated chemical changes are discussed.

Effects of elevated growth temperature and enhanced atmospheric vapour pressure deficit on needle and root terpenoid contents of two Douglas fir provenances

“…MT, monoterpene; MT-O, oxygenated monoterpenoid; MT-A, acetylated monoterpenoid; ST-O, oxygenated sesquiterpenoid. good agreement with published data (2-43 mg g −1 DW: Lerdau et al, 1995;Constable et al, 1999;Litvak et al, 2002;Pureswaran et al, 2004; and 1-11 mg g −1 FW: Gambliel and Cates, 1995;Zou and Cates, 1995;Giunta et al, 2016;Kleiber et al, 2017). Also the terpenoid composition was comparable to those found in these studies, where the needles were found to mainly contain monoterpenes and acetylated monoterpenoids.…”

Differences in isoprenoid-mediated energy dissipation pathways between coastal and interior Douglas-fir seedlings in response to drought

“…interior Douglas fir provenance, Giunta et al (2016) observed emission rates of 910±430 ng g -1 561 FW h -1 and contents of which were close to the ones found in the present work (ca. 13 µg g -1 562 DW).…”

“…In addition to their 118 significance in plant response to abiotic stress, volatile isoprenoids play an important role in 119 plant protection against herbivores and in multitrophic plant-herbivore-predator interactions 120 (Baldwin 2010). Particularly conifers, including Douglas fir, possess large pools of volatile 121 isoprenoids in nearly all tissues required for biotic stress defence (Giunta et al 2016). Interior 122 and coastal Douglas-fir provenances have been shown to vary in pool sizes and composition of 123 stored monoterpenes (Junker et al 2017;Kleiber et al 2017).…”

Forest Decline Triggered by Phloem Parasitism-Related Biotic Factors in Aleppo Pine (Pinus halepensis)

“…Since C. P. pini is a parasite of the phloem, changes in terpenoid composition must be also expected as a reaction to pathogenic infection [42]. Variations in these compounds as a response to biotic attacks have been largely reported [43][44][45][46][47]. For instance, Achotegui-Castells et al, [48] described a positive relation between the concentration of terpenoids in Cupressus sempervivens infected by Seiridium cardinale, which causes the progressive infection known as cypress canker.…”