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

A large forested landscape (18 640 ha) located in Michigan's central Upper Peninsula was examined to estimate current and pre-European mineral soil ca rbon (C) content. Utilizing current forest stand information and pre-Europe an settlement forest data, a landscape level soil C estimate was made for e ach time period and the change in soil C over the 150-year interval was qua ntified. Soil, forest type, and age class information were entered into a g eographical information system (GIS); high medium, and low C levels were as signed 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 value s was determined for each soil mapping unit and vegetation combination, and a percent C value was estimated based on previously assigned C levels. Est imates of average percent C were calculated for both current and pre-Europe an 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 c hanges 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 sh ift from hemlock and conifer forest types to hardwoods and mixed pine/hardw ood forests since European settlement, there has been a reduction of the av erage landscape level soil C on a g/m(2) basis. The net reduction in minera l 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 E uropean settlement of the area. (C) 1999 Elsevier Science B.V. All rights r eserved.