Terpene profile of one-seed juniper saplings explains differential herbivory by small ruminants

TitleTerpene profile of one-seed juniper saplings explains differential herbivory by small ruminants
Publication TypeConference Proceedings
Year of Publication2012
AuthorsUtsumi SA, Cibils AF, Estell R.E.
Conference Name17th Wildland Shrub Symposium
Volumep. 30
Date Published05/2012
PublisherWildland Shrub Symposium
Conference LocationLas Cruces, NM
ARIS Log Number286346
Abstract

A study was conducted in central New Mexico to examine the relationship between terpene profile and one-seed juniper sapling herbivory by sheep and goats. Fifteen does (47.9 ± 1.1 kg) and four ewes (69.2 ± 0.9 kg) were allotted to 16 paddocks (20 x 30m) for 6 days in summer 2006 and spring 2007. Leaves and twigs from 311 browsed saplings (small [< 0.5 m], medium [0.5-1.0 m] or tall [>1.0 m] saplings that received low [< 33%], moderate [33-66%] or heavy [> 66%] herbivory) were collected the same day they were browsed and stored for chemical analysis. The terpene profile contained a total of 66 compounds that included a diverse set of hydrocarbon and oxygenated mono- and sesquiterpenes and a few diterpenes. Total terpene concentration was higher (P < 0.001) in spring (20.6 ± 0.5 mg/g; mean ± SE) than summer (16.7 ± 0.3 mg/g), lower (P < 0.001) in small saplings (16.5 ± 0.6 mg/g) compared to medium (19.8 ± 0.4 mg/g) and tall (19.5 ± 0.4 mg/g) saplings and lower (P < 0.001) in heavily defoliated saplings (16.1 ± 0.4 mg/g) vs. moderately (18.7 ± 0.5 mg/g) or lightly (21.2 ± 0.6 mg/g) browsed counterparts. A subset of 14 compounds ([E]-ß-farnesene, cis-sabinene hydrate, bornyl acetate, '-eudesmol, germacrene A, cis-piperitol, cis-p-menth-2-en-1-ol, trans-piperitol acetate + terpin-4-ol acetate, [Z]-ß-ocimene, terpin-4-ol, camphene hydrate, a-humelene, 8-a-11-elemodiol, ß-elemene), most of which occurred at relatively low concentrations, explained 45% of sapling discrimination (P < 0.001) into high, moderate and low herbivory categories. Results support the hypothesis that one-seed juniper terpene chemistry is related to the extent of sapling herbivory by small ruminants, sapling size, and season.