Landscape scale forest composition and spatial structure: A comparison of the presettlement General Land Office Survey and the 1990 forest inventory in northeastern Minnesota.

摘要

Initial timber harvesting in Minnesota occurred prior to formal vegetation surveys. Consequently, little is known about species composition patterns, associations with soils, geology, and spatial structural relationships of these forests. Species response patterns to natural disturbance regimes however are well known from this region, they were fire dependent. However, fire suppression policy has been so successful and the introduction of initial harvesting was so complete that resource managers and ecologists are now concerned with the consequence of substituting one disturbance regime for another. This work was conducted at the landscape-scale (3.2 million hectares) to improve our understanding of the relationships of biodiversity and disturbance regimes in a southern boreal forest landscape.; I reconstructed the presettlement forest vegetation in northeastern Minnesota using General Land Office Survey Records (1853 and 1917) from the Arrowhead Region of the state. A geographical information systems data base was established that includes digital maps of the survey records, physiographic zones, geology, and soils. I examined species composition patterns, associations with physical environmental factors and spatial structural relationships to improve our understanding of the presettlement forest.; Results profile a low diversity forest with complex spatial autocorrelated structure that was influenced by several factors including, fire, geological materials, physiographic zones, soils, and species clustering tendencies and regeneration strategies.; Change in this forest following the introduction of logging and the suppression of fire was assessed using the presettlement records and 1990 East Wide Forest Inventory and Analysis Survey data base. Species composition and proportional basal area was assessed from these records. I conducted this regional change assessment aggregating presettlement and logging-era plot records within 253 10km x 10km cells.; Results show that substantial changes to the relative abundance, proportional basal area and spatial distribution patterns of species across physiographic zones, and soils has occurred. White pine was a dominant or co-dominant species in 45% of the presettlement forest. Aspen has become the regional dominant or co-dominant species in 83% of the forest. Forest community types with no presettlement-era analog occur in 46% of region. Major declines in white pine and larch were noted.