Native American impact on past forest composition inferred from species distribution models, Chautauqua County, New York

Little consensus surrounds the extent of Native American impacts upon tree species composition in Eastern North America, prior to European-American settlement (presettlement). Native American land-use practices (e.g., forest clearance and burning) likely altered forest composition, but the spatial extent of these alterations remains vaguely quantified. Previous research has attempted to quantify the spatial extent of clearance practices, but little research has addressed the more subtle alterations to tree species composition resulting from Native American land use. Research has also inadequately distinguished between environmental and anthropogenic controls upon tree species composition, leaving open the possibility that, instead of modifying forest composition, Native American societies instead settled where favored tree species were already present. This study employed species distribution models (SDMs) trained from tree species data within presettlement land survey records (PLSRs), in order to understand Native American impacts upon presettlement tree species composition in Chautauqua County, New York. Using historical and archaeological data, this study developed Native American variables (NAVs), which represented human accessibility to features of Iroquoian settlement. This study then modeled the distribution of tree species in relation to both environmental variables and NAVs. Notable results indicate that NAVs significantly improved the predictive performance of SDMs for mast-bearing taxa, such as oak (Quercus spp.), chestnut (Castanea dentata (Marsh.) Borkh.), and hickory (Carya spp.). Under a simulated absence of Iroquoian settlement, the amount of suitable area in Chautauqua County decreased by 2 to 23 percentage points for five mast-bearing taxa, depending upon species and modeling procedure. Results imply that Iroquoian alterations to tree species composition covered a larger spatial extent, in comparison to previous estimates of the spatial extent of clearance practices in Iroquoian regions. Yet, the majority of forest compositional modifications occurred within 10 to 15 km of village sites. This study offers a novel methodology for quantifying Native American impacts upon past tree species composition, and suggests that Iroquoian land-use practices of the early Historic era shaped forest compositional patterns at local extents in one region of presettlement Eastern North America.