Authors: Matthew Trumper*, University of Minnesota, Daniel Griffin, University of Minnesota, Kendra K McLauchlan, Kansas State University
Topics: Paleoenvironmental Change, Physical Geography
Keywords: fire, dendrochronology, nitrogen, synchrony, savanna
Session Type: Virtual Paper
Start / End Time: 9:35 AM / 10:50 AM
Room: Virtual 30
Presentation File: No File Uploaded
Ecologists argue that fire frequency is a principal regulation on nutrient cycling and plant productivity across forest and savanna ecosystems. However, this mainstay in ecological canon draws heavily on short timescale experimentation and observational datasets. To investigate these processes on longer timescales, we leveraged a long running prescribed burn experiment in an oak savanna (1964–2020) at the Cedar Creek Ecosystem Science Reserve, Minnesota to test hypotheses on nutrient cycling and tree-level productivity within and between fire treatments. Sampling nearly 200 bur oak (Quercus macrocarpa) trees across five burn treatments, we developed precisely-dated time series of ring width (N = 398) and tree-ring wood nitrogen (N = 16) to evaluate how fire frequency influences synchrony in tree-ring width and wood nitrogen isotopes across space and time. These experimental burn treatments varied in temporal onset of burning and burn frequency but were consistent in overstory species representation, soil characteristics, and topography. Burn frequency ranged from an unburned control to a unit burned four out of five years during the past 55 years. Our results indicated stronger within-unit synchrony in δ15N relative to ring-width data. Meanwhile, we found mixed evidence for variation in δ15N and ring width synchrony due to long-term fire frequency after synthesizing data across experimental burn units.