CARBON STORAGE IN UPLAND FORESTS OF THE LAKE STATES

Carbon storage and dynamics are receiving increasing attention because of the hypothesized role of CO2 in global climate change. This study was carried out to determine total C storage in Lake States' forests, including C in biomass, forest floor, and mineral soil. Over-story trees were measured and samples of both forest floor and mineral soil (to 1 m) were collected from plots in 169 forest stands across Minnesota, Wisconsin, and Michigan. Five forest types were represented: balsam fir, Abies balsamea (L.) Mill.; jack pine, Pinus banksiana Lamb.; red pine, P. resinosa Ait.; aspen, Populus tremuloides Michx.; and northern hardwoods dominated by sugar maple, Acer saccharum Marsh. There were no strong geographic trends in C storage in biomass, forest floor, or mineral soil across the study area. Storage differed significantly among forest types. Each major C pool was related to a different set of descriptors. Total C storage, the sum of all pools, was related to forest type, stand age, available water, actual evapotranspiration, and soil day content, explaining about 65% of the variation. Use of soil and site descriptors did not completely account for the strong effects of forest type on C storage. Differences in the size of C pools, as related to time since disturbance and forest type, indicate that C storage in forests of the Lake States can be influenced by forest management activities. Patterns of C storage in these moist temperate ecosystems are not as strongly influenced by climatic variables as is C storage in grasslands to the west.