Multiple scale composition and spatial distribution patterns of the north-eastern Minnesota presettlement forest

1 Bearing tree data were used to characterize the composition and spatial s tructure of the southern boreal presettlement forest in north-eastern Minne sota, United States of America. Data collected during the General Land Offi ce Survey (GLO) between 1853 and 1917, represents 35 324 samples (each with 1-4 trees) in a 3.2 million-hectare landscape. Nine tree species contribut ed at least 1% to the overall composition. Individuals of white pine and re d pine were larger than all other species and represented 9% of the tree po pulation, while accounting for 27% of the standing basal area. Black spruce , paper birch and larch, the three most abundant species, collectively acco unted for 51% of the population and 38% of the basal area. 2 Eight physiographic zones were characterized by differences in glacial hi stories, geological surfaces, soil complexes and topographic properties, an d supported different compositional mixes of the nine important species. 3 Fifty-six per cent of all four-tree plots had three or four individuals o f a single species. This level of conspecific aggregation is an order of ma gnitude greater than would be expected based on a random distribution of th e same population of trees and species. Jack pine had the greatest plot-sca le aggregation, with 45% of all plots containing jack pine trees having thr ee or four jack pine individuals. Jaccard association of similarity values of species co-occurrence ranged from less than 0.05 to 0.24, indicating lim ited plot-scale interspecific associations. 4 Landscape spatial patterns of the species were measured at two spatial sc ales, 1-10 km and from 5 to 50 km. Conspecific autocorrelation patterns wer e positive while interspecific autocorrelation patterns tended to be either neutral or negative. Hence, plots dominated by any given species tended to spatially aggregate near other such plots, out to substantial distances. 5 Forest tree spatial patterns reflect complex fine to landscape-scale rela tionships involving environmental factors, disturbance events and regenerat ion strategies. Management and long-term conservation of forest landscapes should consider multiscale patterns in order to re-establish forest structu ral properties eliminated following the disruption of natural disturbance p rocesses.