Differences in chemical composition between browsed and non-browsed Juniperus ashei Buch. Trees
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Leaf secondary compounds were examined in browsed and non-browsed Juniperus ashei trees to identify selective browsing patterns by goats and deer. Analysis of volatile leaf oils (terpenoids) revealed that the browsed trees were lower in total oil than non-browsed trees (2.18 vs. 3.46%, DW basis). Extractable and fiber-bound condensed tannins (CT) were not different but protein-bound CT concentrations were greater in browsed trees. Among digestibility measures (NDF, ADF, IVDMD), IVDMD was greater in non-browsed leaves. Terpene components analyzed on a percent total oil basis had 3 differences versus 12 significant differences on a mg/g DW basis. The terpenoid components profile differed little between browsed and non-browsed trees. Total CT are negatively associated with oil yields. No association was found between crude protein and oil yields or between digestibility (IVDMD, NDF, ADF) and oil yields. The question of whether individual plants or populations may invest less in CT when greater amounts of terpenes are produced (or vice-versa) may have evolutionary implications since individual browsers or populations may adapt to consuming or avoiding either CT or terpenes. The fact that browsed tree leaves were less digestible than non-browsed tree leaves may be a result of complex interactions between CT, terpenes, fiber, and nutrients. 2012 Elsevier Ltd.
