Building a Quercus macrocarpa (Bur Oak) Tree Ring Network to Reconstruct Historical Climate and Address the Issue of Forest Mortality in Nerstrand Big Woods State Park

Increased precipitation over the past decade has elevated soil moisture in Southeastern Minnesota. This higher presence of water in the soil has caused increased tree mortality within the Big Woods ecosystem, most notably in Nerstrand Big Woods State Park. Instrumental climate data is only available in the region for the past 125 years. A lack of long-term climate data for Rice County, MN creates uncertainty as to how unusual this phenomenon of increased soil moisture is for the area. Trees can be an important source of historical climate data due to patterns of annual growth. Tree rings form through annual cycles of dormancy and activity that result in the production of a ring, defined as a new layer of vessels, fibers, and other woody cells. Variations in the width of these rings reflect changes in regional moisture availability and can be used to reconstruct historical rainfall or other climate variables. Analyzing annual growth from Bur Oak located near Nerstrand Big Woods State Park could extend current climate records further into the past than the current instrumental record, presenting the opportunity to look for long-term climate patterns. This study constructs a tree-ring network and chronology from eight Quercus macrocarpa (Bur Oak) samples in order to infer historical climatic conditions from Ring Width Index (RWI), a measure of average annual growth. No significant correlations were found between RWI and seasonal climate data at the time of this study; however this is likely due to small sample size. With the addition of more core samples, the RWI chronology and correlations to climate could improve