Herbivory alters plant chemistry thereby affecting subsequent palatability for the same or different herbivore species. Balsam fir is an important food for various insect and mammalian herbivores that consume tissues at different times of year. In eastern Canada, intense selective browsing of this tree species by ungulates has impeded natural regeneration of fir-dominated forests. Our objective was to determine whether late-season (simulated) browsing of apical and lateral branches affected the defense chemistry of emerging foliage of balsam fir saplings in the following season. At each of five locations in the vicinity of Gros Morne National Park, western Newfoundland, four browsing treatments were imposed in the late growing season on healthy fir saplings; apical, lateral, apical + lateral, and no browsing. In the following season, newly expanded and previous-year needles were collected shortly after bud break and analyzed for total phenols and condensed tannins. Browsing treatments had no effect on levels of these defense chemicals in either needle age class indicating the lack of an induced chemical response or preferential defense of the apical versus lateral shoots. New foliage appeared to be better defended than previous-year foliage. Neither phenol nor tannin levels were related to canopy closure or height and diameter of saplings; however, foliar phenol concentration was positively related to soil pH for both age classes of fir needle indicating a possible relationship between soil characteristics and plant secondary metabolites. Levels of both phenols and tannins in current-year needles were positively related to those of previous-year needles, whereas the concentration of phenols and tannins were negatively related for previous-year needles only. Our results support the premise that the main antiherbivore strategy of balsam fir is tolerance of intense browsing.

草食动物改变了植物的化学性质，从而影响了相同或不同草食动物种类的后续适口性。苦瓜冷杉是重要的食物，对于一年四季在不同时间消耗组织的各种昆虫和哺乳动物食草动物而言。在加拿大东部，有蹄类动物对这种树种的强烈选择性浏览阻碍了冷杉为主的森林的自然再生。我们的目的是确定在下一个季节中，季末（模拟）的顶端和外侧分支浏览是否会影响香脂杉木幼树的新兴叶片的防御化学。在纽芬兰西部的格罗斯莫恩国家公园附近的五个地点中的每个地点，在生长后期都对健康的杉木树苗进行了四次浏览处理。顶部，侧面，顶部+侧面，并且没有浏览。在接下来的季节 芽断裂后不久收集新近扩张的针和前一年的针，并分析其总酚和单宁含量。在针龄的年龄中，浏览处理对这些防御化学物质的水平均没有影响，表明缺乏诱导的化学反应或对顶芽和侧芽的优先防御。与前一年的叶子相比，新叶子的防御似乎更好。苯酚和单宁的含量与树冠的封闭或树苗的高度和直径均无关。然而，两种年龄等级的杉木针叶叶酚浓度与土壤pH呈正相关，表明土壤特性与植物次生代谢产物之间可能存在关系。当年针头中酚和单宁的水平与前一年针头呈正相关，而酚和单宁的浓度仅与前一年的针呈负相关。我们的研究结果支持了香脂冷杉的主要抗草食动物策略是耐受强烈浏览的前提。