A legacy ecological survey and species distribution models reveal the mid-20th century niche of American chestnut (Castanea dentata [Marsh.] Borkh.) in Monroe County, New York State, US

The American chestnut (Castanea dentata [Marsh.] Borkh) was an important tree in eastern US forests until its functional extinction in the early 20th century by an invasive fungal blight. Backcross breeding and genetic engineering efforts have sought to develop a blight-resistant cultivar. Anticipating the species’ restoration, researchers have developed species distribution models (SDMs) to model potential locations for suitable habitat. SDMs have modeled either the pre-European-American or present distribution of the species. This study modeled mid-20th century chestnut distribution in Monroe County, New York State, US, utilizing a unique dataset from a county-wide ecological survey conducted 1938–1940. Employing the Maximum Entropy technique, this study modeled distribution at 10 m resolution in relation to soil and topographic predictors. This study produced good models (i.e., mean area under the curve [AUC] measure of 0.851) that suggested chestnut preferred well-drained, acidic, sandy, and nutrient-deficient soils in gently sloping terrain. In particular, it suggested that soil permeability rate and pH were the two most important predictors of its mid-20th century distribution, with percent contribution measures of 47.9 and 15.0 %, respectively. Chestnut was found in nearly the fastest-draining soils in the county, and with pH values of 5.3–6.8. This study affirmed the findings from previous SDMs regarding determinants of the chestnut’s past and present distribution, while also specifying relationships with environmental predictors to generate a prediction for chestnut habitat suitability in the study area.