Forest development and stand dynamics in the Driftless Area of Wisconsin: Implications for oak regeneration and management

by

Megan L. Buchanan, Kurt F. Kipfmueller, Anthony W. D’Amato

University of Minnesota (MLB), University of Minnesota (KFK), University of Vermont (AWD)

Abstract – Throughout the deciduous forests of the eastern United States, oak (Quercus) regeneration has exhibited a decline in stands historically dominated by oak species. Factors causing the reduction in oak regeneration include disturbance regime alterations, changes in climate, and historical land-use legacies. This research aims to elucidate the relative importance and site-specific nature of the factors influencing oak regeneration and to identify interactions between drivers. In the Wisconsin Driftless Area (WDA), the decline of oak regeneration is variable and influenced by a site’s structural development. To quantify variation in stand structural characteristics, we collected forest inventory, dendrochronological, regeneration, and coarse woody debris data from 11 sites distributed throughout the WDA. To summarize structural variation across the region, several site-level metrics were calculated: density and basal area by size class, standard deviation of dbh, Gini coefficient, Shannon index, average q-ratio, and diameter distribution curve forms. The developmental stage of each site was calculated using a modified version of the decision tree developed by Lorimer and Halpin (2014). Site-level basal area of trees ≥10 cm dbh ranged between 17.2 and 45.4 m2 per hectare and density ranged from 325.0 to 687.5 trees per hectare. The stages of structural development identified across sites included pole, mature-sapling mosaic, mature, and early transition old growth. Structural complexity was also variable across the WDA as evidenced by the range of site-level metrics. Future analyses will investigate the relationship between stand structure, developmental stage, land-use history, disturbance history, abiotic conditions, and oak regeneration.