  We present a gridded 8 km-resolution data product of the estimated
composition of tree taxa at the time of Euro-American settlement of the
northeastern United States and the statistical methodology used to produce the
product from trees recorded by land surveyors. Composition is defined as the
proportion of stems larger than approximately 20 cm diameter at breast height
for 22 tree taxa, generally at the genus level. The data come from
settlement-era public survey records that are transcribed and then aggregated
spatially, giving count data. The domain is divided into two regions, eastern
(Maine to Ohio) and midwestern (Indiana to Minnesota). Public Land Survey point
data in the midwestern region (ca. 0.8-km resolution) are aggregated to a
regular 8 km grid, while data in the eastern region, from Town Proprietor
Surveys, are aggregated at the township level in irregularly-shaped local
administrative units. The product is based on a Bayesian statistical model fit
to the count data that estimates composition on a regular 8 km grid across the
entire domain. The statistical model is designed to handle data from both the
regular grid and the irregularly-shaped townships and allows us to estimate
composition at locations with no data and to smooth over noise caused by
limited counts in locations with data. The model also allows us to quantify
uncertainty in our composition estimates, making the product suitable for
applications employing data assimilation. We expect this data product to be
useful for understanding the state of vegetation in the northeastern United
States prior to large-scale Euro-American settlement. In addition to specific
regional questions, the data product can also serve as a baseline against which
to investigate how forests and ecosystems change after intensive settlement.
The data product is available at the NIS data portal as version 1.0.
