Forest Sequences in the North Central States

Publisher Website
Google Scholar
Abstract
15 postglacial pollen profiles from bogs in Illinois, Indiana, Michigan and Ohio are figured, of which 13 were previously unpublished. With one exception, in northern Michigan, all are in the central deciduous region. Due to differences in sedimentary history, drainage and fire, not all bogs represent the same time span. However, 4 correlative levels have been established for the series, 1 or more of which is exhibited by each profile. These are as follows IV. Oak-hickory maximum; III. Beech maximum; II. Pine-(oak) maximum; I. Spruce-fir maximum. The shift from spruce-fir to pine indicates decreasing meso-phytism and, following Cowles, is designated as a retrogression. This is true of the subsequent shift from beech to oak-hickory. These 2 periods of retrogression in postglacial time are believed to represent periods of relatively less humid climate and are considered adequate to account for relicts of continental vegetation in the central deciduous region. Of the 15 profiles, 3 exhibit a 2d increase of beech following the oak-hickory maximum, but this is apparently not general.

This publication has 2 references indexed in Scilit: