Phytochemical traits underlie genotypic variation in susceptibility of quaking aspen (Populus tremuloides) to browsing by a keystone forest ungulate

1.Overbrowsing by ungulates is a major cause of poor aspen stand regeneration across North America and Eurasia. In general, factors driving ungulate browser preferences include concentrations of plant secondary compounds and the nutritional composition (non-structural carbohydrates, protein, and minerals) of foliage. While each of these phytochemical factors has been shown to independently influence ungulate preference, the relative impact of each factor is unknown, as no study to date has examined them simultaneously.
2.Plant fitness depends not only on the capacity of plants to resist browsing, but also on their capacity to tolerate browsing once it has occurred. Little is known of aspen tolerance to browsing, which inflicts a different form of damage than insect herbivory.
3.We employed multiple aspen genotypes, replicate trees of which were subjected to different soil nutrient treatments, to investigate: 1) the effects of aspen genotype, nutrient treatment, and genotype x nutrient...