Disturbances Over Space and Time: Edge Effects on the Sylvania Wilderness Old-Growth Fores

The majority of the world's remaining forests are surrounded by non-forested land use. Old-growth forests, reservoirs of biodiversity and habitat refugia, are particularly vulnerable to these edge effects: these stands are isolated and comprise less than 1% of forests globally and in the western Great Lakes states. We researched landscape changes over space and time to assess edge effects on an old-growth tract in Upper Michigan, the Sylvania Wilderness Area. Spatially, we evaluated the location, spatial extent, and magnitudes of these effects using modern vegetation transects that crossed the Sylvania Wilderness border. Temporally, we compared the legacy effect (i.e., disturbances that persist over time) of multiple disturbances by tracking microfossil changes in high-resolution, freeze-cored paleorecords from lakes that vary in disturbance history relative to Sylvania's border.;To test the spatial edge effect, we selected best-fit generalized linear mixed models with a range of possible edge effect locations and widths of effect. To test the temporal edge effect and locate periods in time of the most rapid taxon shifts, we applied a derivative-based change point analysis (the jerk) and a cluster analysis that selected the highest-magnitude peaks; we tested the synchrony of these peaks to disturbance events using Ripley's K-function. We found spatial edge effects up to 625 m into the Sylvania Wilderness. Wide zones of change occurred across the wilderness border, while zones of change farther from the edge were narrower, suggesting distinct environments establish beyond edge-influenced border habitat. In paleorecords, we found divergent trajectories among wilderness and non-wilderness lakes, lower magnitudes of response in wilderness paleorecords, significant synchrony among disturbance events and derivative-based change points, and strong responses in specific taxa (e.g. dinoflagellate cysts, Isoetes ) following disturbance events. This edge effect analysis indicates legacy effects manifest quickly (within 10 years) and have a potential duration of effect of 45 years. Implementing a conservative buffer zone (e.g., 500 m), applying high-resolution sampling to proximate lakes, and tracking dinocyst abundance to estimate taxon responses to disturbances may help sustain long-term ecosystem trajectories. This work highlights the need for continuing research on edge effects to address ongoing environmental disturbances affecting old-growth forests.