Insect-driven Changes in Autumn Phenology

George Mason University, Fairfax VA

Investigators

Abstract

This project will explore how leaf-feeding insects may determine leaf color and the timing of autumn leaf fall. The project challenges two traditional beliefs about autumn foliage color: that the timing and degree of autumn coloration can be predicted exclusively from the temperature, moisture, and day length conditions experienced by a tree, and that the fall colors we enjoy are simply those exposed as green pigment, in the form of chlorophyll, is degraded. In particular, the research will test the idea that insect damage can either advance or delay the timing of leaf loss and can alter presence of anthocycanins, the compounds responsible for orange, red, and purple leaf colors. By examining a suite of deciduous trees common in eastern North America, this study will contrast how leaf damage by insects affects tree species that use anthocyanins compared to those that use other pigments. Chemical changes in leaves, including the production of colors, are a major way in which plants recover necessary nutrients for growth and reproduction in future seasons. Therefore, a second part of this research will determine how trees that differ in the amount and timing of autumn coloration differ in how and when they produce new leaves in the subsequent spring. A long term goal of this work is to predict how insects change the timing of plant growth in ways that affect the sustainability and diversity of forests. These ecological studies will contribute to a better ability to forecast how well trees prepare for winter. Such knowledge is critical to predicting how biological communities of plants and leaf-eating insects in temperate forests will change with increasing global temperatures. Additionally, it will help us determine if insects that cause widespread damage to forests may potentially impact fall foliage tourism revenue by delaying or decreasing autumn coloration across the landscape. Finally, this award will support the training of graduate and undergraduate students in interdisciplinary research in botany, entomology, and climate change.