2. Geologic and Edaphic Factors Influencing Susceptibility of Forest Soils to Environmental Change

There is great diversity in the structure and function of the northern forest across the 20-state portion of the United States considered in this book. The interplay of many factors accounts for the mosaic of ecological regimes across the region. In particular, climate, physiography, geology, and soils influence dominance and distribution of vegetation communities across the region. This chapter provides a review of the ecology of the northern forest, emphasizing the role of geology and soils. The chapter begins with descriptive material reviewing the physiog-raphy, bedrock geology, and soils of the various provinces that constitute the northern forest. The distribution of vegetation communities and the role of climate, while of prime importance in defining the ecology of the region, are given limited coverage here as these are discussed more thoroughly elsewhere in this volume (see Chapters 1 and 3). However, to the extent that climate and vegetation are important soil-forming factors (Jenny, 1941), their characteristics in each province are summarized here