A Legacy Ecological Survey and Species Distribution Models of Mid-20th C. American Chestnut in Monroe County

Summary

This study created a map of predicted geographic distribution of American chestnut in the mid-20th century in Monroe County, New York; chestnut is a functionally extinct tree species that scientists are attempting to bring back via breeding and genetic efforts.

Abstract

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.

Main research questions 

1. Where was American chestnut located historically? 

2. What environmental conditions (e.g. soil, terrain) did chestnut prefer?

What the research builds on

Previous studies have modeled the pre-Euro-American and current distribution of American chestnut, but few studies have modeled its distribution around the time of its demise using quality ecological datasets.

What the research add to the discussion

It confirms the importance of many conditions in shaping chestnut geographic distribution: "well-drained, acidic, sandy, and nutrient-deficient soils in gently sloping terrain."

Novel methodology

This study utilized a mid-20th century dataset of chestnut locations produced by ecologists using Great Depression-era funds. It utilized these data in correlative models of chestnut distribution.

Implications for society 

This study can help guide the restoration of American chestnut, assuming that breeding and/or genetic engineering efforts yield a viable chestnut that can be released into the wild.