A landscape level comparison of pre-European settlement and current soil carbon content of a forested landscape in upper Michigan

Abstract

A large forested landscape (18 640 ha) located in Michigan's central Upper Peninsula was examined to estimate current and pre-European mineral soil carbon (C) content. Utilizing current forest stand information and pre-European settlement forest data, a landscape level soil C estimate was made for each time period and the change in soil C over the 150-year interval was quantified. Soil, forest type, and age class information were entered into a geographical information system (GIS); high medium, and low C levels were assigned to soils based on forest type and age class groupings. Using organic matter data from soil surveys of the area, a range of mineral soil C values was determined for each soil mapping unit and vegetation combination, and a percent C value was estimated based on previously assigned C levels. Estimates of average percent C were calculated for both current and pre-European landscapes to be 9.7% and 11.7%, respectively. Overall, there appears to be a decrease in soil C content since European settlement as a result of changes in forest cover and land use. Due to the strong relationship between forest type and soil C content, an increase of urban/brush areas, and a shift from hemlock and conifer forest types to hardwoods and mixed pine/hardwood forests since European settlement, there has been a reduction of the average landscape level soil C on a g/m 2 basis. The net reduction in mineral soil C content on this landscape is estimated to be approximately 0.3 to 0.8 Tg C (in the upper 10–25 cm of mineral soil) over the 150 years since European settlement of the area.