Spatial characteristics of early successional habitat across the Upper Great Lakes states

Creation and management of early successional forest (ESF) is needed to halt and reverse declines of bird species dependent on pioneering plant species or young forests. ESF-dependent bird species require specific structural forest classes and are sensitive to forest age (a surrogate for forest structure), patch size, proximity to patch edges, and the juxtaposition of forest age classes. To date, ESF conservation plans have relied on spatially inexplicit data, lacking patch and landscape metrics, to set habitat goals and to track habitat trends. In a previous study, we used Landsat time series stacks and a vegetation-change-tracker algorithm to track forest canopy disturbances and subsequent regrowth from 1990 to 2009 across the Upper Great Lakes Young Forest Initiative region. Based on canopy disturbance histories, we assigned forest age classes to forest classes of the National Land Cover Database of 2011. In the present study, we used this spatial product to assess areas, patch and edge metrics, and land protection statuses of deciduous-mixed forest and woody wetland age classes. We defined ESF using four 5-year-age classes (1-5, 6-10, 11-15, 16-20 years old) and their aggregate (1-20 years old) whereas forest >20 years old was referred to as 'persisting'. Aggregated across 5-year-age classes, ESF of deciduous-mixed forest covered 3.4% and 0.9% of Bird Conservation Regions (BCR) 12 (Boreal Hardwood Transition) and 23 (Prairie Hardwood Transition), respectively, whereas woody wetland ESF constituted 1.0% and 0.2% of the same BCRs. For both deciduous-mixed forest and woody wetlands, ESF often occurred in patches ⩾1 ha, but most ESF also occurred near patch edges created by adjacencies with persisting forest. Most ESF fell on lands with an unprotected or unknown protection status regardless of forest class. Regionally, ESF covered less area, occurred in smaller patches and nearer to edges, and more often fell on lands of unprotected or unknown protection status in BCR 23 than in BCR 12. Our results advance ESF conservation by providing insight into spatial characteristics that influence habitat quality and by establishing a baseline for habitat management planning and monitoring.