Paleoecological perspective on restoration goals: Vegetation, fire, and climate on the northwestern Wisconsin sand plain

Maps from the Public Land Survey (PLS) provide insight into landscape-scale vegetation patterns before widespread land clearance, but may not be a feasible target for restoration given changing climate. We used sediment cores from 8 small lakes to investigate the temporal/spatial variability of landscape-scale vegetation patterns over several thousand years on a sand plain in northwestern Wisconsin. Landscape context appears to have influenced the sensitivity of vegetation to Little Ice Age (LIA) climate change. We classified soil texture and exposure to fire within a 25km² area around each site using aerial coverage estimates of soil type. Upland soils fell into two groups, loamy sand and sand, and each soil type contained two fire exposure classes defined by the cover of water and muck soils. Sites on loamy sand soils exhibited greater change in species composition over time. While pollen assemblages at sites on sandy soils changed little, oak was replaced by jack-red pine on loamy sand over several thousand years. A rapid decrease in oak abundance occurred at several sites about 1500 years ago, sometimes shifting to pine within 50 years, and white pine abundance increased on loamy sand soils at the beginning of the LIA about 700 years ago. PLS vegetation types were established during the LIA, but the spatial pattern of vegetation observed in the PLS data continued changing until the time of the PLS survey. Within soil types, sites surrounded by abundant water and muck showed a decrease in charcoal accumulation rates (CHAR) during the LIA, while CHAR increased at the most exposed sites, suggesting an increase in fuel production or spread of fires. Given the dynamic nature of vegetation and disturbance patterns, large blocks of contiguous habitat will be needed to accommodate a shifting mosaic of vegetation types that can respond to changing climate.