Major
Marine Biology
Minor(s)
Spanish
Advisor
Evan Preisser
Advisor Department
Biological Sciences
Date
5-2019
Keywords
Chemical Phenology; Eastern Hemlock; Chemical Ecology; Phenology
Abstract
Phenology is the study of seasonally timed developmental events that are driven by environmental cues. Phenolic compounds and terpenoids are the two main classes of secondary metabolites present in conifer needles, and speaking generally, they correlate with needle age. Understanding the phenology of secondary metabolites is important, since variation in these compounds can affect a tree’s resistance to pest and pathogen attack. Terpenoids function in a wide array of ecological processes vital to conifer survival, including regulating forest dynamics through allelopathic inhibition of seed germination, altering rates of soil nutrient cycling and nitrification, and conferring resistance to pathogenic fungi and insect herbivory. Phenolics are equally diverse, contributing to needle structural development, toughness and defense against insect herbivore attack. We present the results of a study evaluating changes in foliar terpenoid and phenolic compounds over the course of a growing season, from April through September with additional time points in December and January, to provide a complete first picture of Eastern Hemlock chemical phenology. The present study aimed to (i) describe temporal patterns of non-volatile alpha-pinene, camphene, diterpene acid and isobornyl acetate concentrations in both expanding needles and mature needles from the previous year’s growth, (ii) to describe temporal patterns of tannin, lignin and total phenolic compound levels in the same foliage classes, and (iii) to identify at what point in the growing season the levels of these metabolites in expanding needles converge on levels present in mature needles. We hypothesized that the relative abundances of structural and defensive metabolites will show an inverse relationship in expanding needles, mature needles will exhibit elevated levels of defensive metabolites during growth, but with less variability than new foliage, and that the levels of all metabolites in new foliage will reach those of mature foliage by the end of the growing season.