Enhanced avian diversity in Wisconsin pine barrens through aggregated timber harvest

摘要

The pine barrens of northwestern Wisconsin are defined by areas of xeric sands with vegetation that is highly susceptible and adapted to fire (Figure 1). Fire frequency in the region prior to settlement by Europeans is unknown (Canham and Loucks 1984), but fires were sufficiently large and frequent to remove most timber and much woody vegetation in some areas, creating large openings called barrens (Curtis 1959). Prior to settlement by Europeans, barrens are estimated to have covered 930,000 hectares in Wisconsin (Curtis 1959) and 2 million hectares in Wisconsin, Minnesota and Michigan (Vora 1993). Presently, large areas of early successional vegetation and many associated species are gone from northwestern Wisconsin. With the advent of fire control in the 1920s, secondary succession and tree planting have resulted in almost complete forestation of the pine barrens, reducing the size and number of early successional habitat patches (Curtis 1959, Gregg 1987, Mossman et al. 1991). Increased anthropogenic edge, decreased patch size, altered microclimate, and altered disturbance regimes typical of managed landscapes (Godron and Forman 1983, Hansson 1992) are all exhibited in Wisconsin pine barrens.