Analysis of daily scale climate observations alongside sub-annual tree-ring data offers new potential for contextualizing climate change in the Great Lakes region. This pilot study combined daily observations from a high-quality station record with a co-located chronology of Pinus resinosa latewood width at Lake Itasca, Minnesota. We evaluate trends in observational data and use multiple methods to compare day-wise aggregated climate observations with tree rings over the eleven-decade common period. The Itasca record exhibited strong increases in warm-season precipitation, minimum temperature in all seasons, and lengthening of the freeze-free season. Correlation analyses verified a strong, multi-month warm-season precipitation response in Pinus resinosa latewood width. Distinct from previous work, daily data analyses were used to fingerprint an ~2-week period starting in late July when rainfall variability was historically a major control on interannual tree growth. Climatologically, the timing of this subseasonal critical climate period corresponds with a relative minimum in mean midsummer precipitation. Since the 1980s, the latewood correlation with midsummer rainfall has vanished, and the seasonal-scale rainfall response diminished considerably. This result, new for Pinus resinosa in Minnesota, is consistent with studies showing a declining relationship between tree growth and drought in the Midwest United States. Further attribution analyses emphasizing daily-scale phenomena are needed to elucidate mechanisms responsible for the tree-growth response to variability, change, and extremes in climate throughout the Great Lakes region, where the biophysical and socioeconomic impacts of climate change are multifaceted issues of increasing urgency.
Bibliographical noteFunding Information:
The lands currently defined as Itasca State Park were frequently used by the Dakota and more recently the Ojibwe, besides its use by earlier cultural groups, prior to European colonization. We acknowledge and are grateful for the opportunity to gather and deploy tree-ring resources from this land to inform our research and findings. We thank the personnel from the Minnesota Department of Natural Resources for granting us sampling permission in Itasca State Park. We also thank the personnel at the University of Minnesota Itasca Biological Station and Laboratories, especially Jonathan Schilling, Lesley Knoll, and Laura Domine, for logistical support and helpful discussions about research in the park. Daniel Brumm, Daniel Crawford, Jared Stachiw, Evan Larson, Lane Johnson, Elizabeth Schneider, and undergraduate students from the University of Wisconsin-Platteville provided critical assistance in the field and laboratory work. We thank the personnel from the Chippewa National Forest and students and staff from the Leech Lake Tribal College STEM Club for their fieldwork assistance and insightful comments and perspectives.
Copyright © 2022 Trumper, Griffin, Montpellier and Kipfmueller.
- bimodal precipitation
- daily observations
- Itasca State Park
- latewood width
- red pine
- warm season hydroclimate