Intra-annual ring width and climate response of red pine in Itasca State Park in north-central Minnesota

Red pine (Pinus resinosa Ait.) of northern Minnesota are part of a growing network of tree-ring chronologies aimed at understanding climate dynamics in the Upper Great Lakes Region. Red pine has been widely used in tree-ring studies of fire and climate variability across its range. Earlier studies have relied primarily on total annual ring width. Here we develop annual and subannual (i.e., earlywood, latewood, and adjusted latewood) chronologies from Itasca State Park to refine our understanding of red pine climate response. Our chronologies extend to the early 18th century and display common growth and cross-dating characteristics indicative of a significant common controlling mechanism. We found that total ring width contains dampened attributes reflective of both the temperature-limited earlywood and moisture-dependent latewood chronologies. The strongest relationship between climate and radial growth is between the adjusted latewood chronology and 3-month summer precipitation, suggesting that overall summer wetness rather than any single summer month primarily limits growth. The ability to disaggregate and improve upon the mixed climate signal of red pine highlights the potential of using intra-annual chronologies to strengthen future climate reconstructions. We hope the methodologies demonstrated here serve as a potential guide for future red pine chronology development in the region.