Oak overstory/reproduction relations in two xeric ecosystems in Michigan

Abstract

Average reproduction density of oaks in the northern pin oak-black oak/ Deschampsia (PBD) ecosystem was approximately half that of the slightly less xeric black oak-white oak/ Vaccinium (BWV) ecosystem. However, when variation in total overstory basal area and the basal area of large oaks (i.e. white oaks, of 30 cm diameter at breast height (dbh) or more and black oaks of 36 cm dbh or more) was accounted for, reproduction density of white oak and the black oak species-group (black, northern red, and northern pin oaks) did not differ significantly ( P > 0.05) between ecosystems. High white oak reproduction density was associated with low stand basal area and high basal area of white oaks of 30 cm dbh or more. In contrast, high black oak reproduction density was associated with high overstory basal area and high basal area of black oaks of 36 cm dbh or more. In both ecosystems, the height of the tallest stem of oak reproduction per 5.5 m 2 plot increased with decreasing overstory density for both white oak and black oaks. For a given overstory density, the frequency of occurrence of all size classes of oak reproduction was greater in the black oak-white oak/ Vaccinium ecosystem than in the pin oak-black oak/ Deschampsia ecosystem.