Upcoming Events
Alexis Garretson M.S. Biology Thesis Defense
Aug 12, 2020, 1:00 - 3:00 PM
Thesis Defense Announcement
To: The George Mason University Community
Candidate: Alexis Garretson
Program: M.S. Biology
Date: August 12, 2020
Time: 1:00 PM
Place: Webex Meeting Information
Meeting link: https://gmu.webex.com/gmu/j.php?MTID=mcf9ab3f3eb6c98a1458f89118a33e15e
Meeting number (access code): 120 061 6953
Meeting password: eEnrqp9VF68
Title: Identifying and projecting novel long-term phenological trends: Integrating heterogeneous data sources
Committee Chair: Dr. Rebecca E. Forkner
Committee Members: Dr. Lorelei Crerar, Dr. Rebecca Dikow
All are invited to attend the defense.
ABSTRACT:
Studies of climate change in deciduous forest communities mainly document the earlier appearance of spring leaves and later senescence in autumn. However, climate change can create novel patterns of growth or shift other aspects of plant phenology. For example, regrowth of leaves after late spring frost damage or increases in herbivory as a result of climate change can generate aseasonal new leaf production in summer and autumn. To determine if such changes have occurred in eastern United States forests, I examined digitized herbarium specimens and citizen-science images of sugar and red maple (Acer saccharum and A. rubrum: Sapindaceae) for the presence/absence of expanding leaves of buds, fruit, flowers, and colored leaves, as well as fungal and herbivory damage. Available herbaria specimens ranged from 1892 to 2017 but were dominated by specimens collected in the 1970s. Citizen science images were largely dominated by specimens observed in the late 2010s and served to verify changes observed in herbaria records. Comparisons of pre- and post-1960 herbaria collections show that maples experienced a lengthening of the time span of new leaf production. Specifically, I document new leaf production in every month from April to September compared to a single peak prior to 1960 of buds and expanding leaves in May. Additionally, decadal comparisons uncovered increases in fall pathogen damage and herbivory over the past 200 years. My results indicate that the effect of climate warming go beyond a simple lengthening of leaf life span and instead radically change the seasonal timing of new leaf production with impacts on multi-trophic interactions. Such novel phenological patterns may require modifications to current climate models of carbon and nutrient sequestration.