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05-19-1997 13:12 612 625 5212 UM FOREST RESOURCES P.03/09 <br />Reiults <br />Forest structure. A total of642 trees were tallied among the 30 plots. 175 of these were >10 cm <br />dbh, and 131 of them were overttoty trees, which had a mean dbh of 31 cm. The total basal was <br />13.4 square meters, or about 29 square meten / hectare. This is a typical basal for mature maple- <br />basswood-oak forest stands in the upper KGdwest. The diameter distribution fbr all trees shows a <br />typical negative exponential shape (fig 1). However, there are so many small saplings that the <br />shape of the distribution for sizable trees is obscured by the scale effect on the graph. In addition, <br />dbh distributions with all of the understory trees shown do not give a good representation of stand <br />structure as it relates to disturbance history. <br />Figure 2 shows overstory trees only. The complex history of the stand is apparent. Trees from <br />45 to 75 cm dbh mostly deviate substantially from forest-grown growth form (rated as 4 or 5 in <br />this analysis). These are trees that existed prior to the establishment of the modem forest (80 <br />years ago or more) in the form of scattered open-grown trees and small groves of trees. The one <br />exception to this is a grove of v^e oaks in the northwest comer of the site arc large and have <br />good forest-grown growth form, indicating that there was a small area (1-2 hectares) of closed- <br />canopy forest there 100-150 years ago. Trees from 25-45 cm dbh have moderate to good forest <br />growth form and are 60-100 years old; they are the main cohort that dominate the current forest <br />and they filled in the open areas that formerly existed around the older trees. Trees from 0-25 cm <br />dbh, that are nevertheless in the canopy, are those that are filling in gaps that form when the older <br />trees (those that were formerly open grown) die. Trees of poor forest grown form were present <br />on 16 of 30 plots, which occurred in ail 6 sampling units. <br />Understory trees are virtually all sugar maple and ironwood, and range in size from 0-25 cm dbh <br />(Fig. 3). These trees will continue to replace the older oaks and sugar maples as they die. <br />Forest composition. Of the 642 trees tallied, 605 are live, and these are heavily dominated by <br />sugar maple and ironwood (89.2% of all live trees). Oaks and basswood make up only a small <br />portion of the stems, but a relatively large proportion of basal area (Table 1). Sugar maple, white <br />t)Uf Qak, red oak and basswood are the dominant species, together composing more than <br />90% of the basal area. A comparison of the basal area dominance of all 30 plots (Table 1), with <br />the six sampling units (Table 2) indicates that the stand is basically dominated by sugar maple, <br />with oaks or basswood scattered at various locations around the site. For example, white oak <br />occurs in abundance (>10%) in sampling units 4 and 6; bur oak in 3 and 6; red oak in 3; and <br />basswood in 2 and 3. In addition, bigtooth aspen occurs in abundance in sampling unit 5, ud red <br />maple in sampling unit 3. Thus, the spatial pattern of the site is a matrix of sugar maple with <br />small groves of the other species emb^ded within lt--a very typical spatial pattern for Midwestern <br />forests.