Interaction of Human Settlement, Vegetation Patterns and Soils in the Northern Minnesota Prairie-Forest Region from the Euro-American Settlement Era to Present

Abstract

From studying pollen and charcoal in lake sediments, scientists have reconstructed the past climate, fire frequency, and intensity as well as the vegetation patterns in the state of Minnesota. They concluded that the climate became wetter since 8000 yr BP ago and fire occurrence was less frequent, and both factors have led to forest invasion into prairie vegetation and shaped the modern day natural landscape in the region. This trend makes the modern-day landscape in Northern Minnesota overtly different from the landscape prior to 4000 yr BP during the mid-Holocene due to change in aridity, temperature and other climatic causes. An additional factor in understanding the past landscape’s relation to the modern landscape is Euro-American settlement and land use patterns in this region over the past two centuries. Both climate- and land-use-induced vegetation change could have significantly affected soils, especially their storage of carbon. To reveal more about the interaction among the three factors, this research utilizes several data sources, including historical and modern aerial imagery, public land survey notes and plat maps, soil survey data and agricultural statistics, to analyze the issue in iterations of comparison. First, to understand how the landscape has changed in Northern Minnesota prairie-forest transition region after the Euro-Americans settled on this land, the Public Land Survey notes and plat maps are examined to generate an understanding of the land cover prior to the settlement; then we compare this understanding of initial landscape to the landscape after the settlement as recorded in 1930s aerial imagery, so that the impacts and changes that Euro-American settlement has made on the landscape will be revealed. Secondly, from comparisons of the earliest aerial images collected in 1930s to the modern day’s aerial images collected in 2015, the relation between human settlement and vegetation pattern, as well as how this relation has changed, can be learned to understand how human settlement has influenced the land cover on this landscape from post the Euro-American settlement period to present. Thirdly, soil survey data will be utilized to study whether there is a mismatch between vegetation pattern and soils in this region at these three points in time: prior- and post-Euro American settlement in late 19th century and the modern days; the spatiotemporal relationship between soil and vegetation patterns may reflect soils’ delayed response to past vegetation change. This research reveals the effects human settlements have on vegetation land cover on this unique vegetation transitional landscape, and understanding these effects could subsequently shed light on researching the impacts on soils and their carbon storage capacity.