The forests of the midwestern United States at Euro-American settlement: Spatial and physical structure based on contemporaneous survey data.

Christopher J Paciorek,John W Williams,Jason S Mclachlan,Charles V Cogbill,David J Mladenoff,Andria Dawson,Jody A Peters,Runguo Zang

doi:10.1371/journal.pone.0246473

Abstract

We present gridded 8 km-resolution data products of the estimated stem density, basal area, and biomass of tree taxa at Euro-American settlement of the midwestern United States during the middle to late 19th century for the states of Minnesota, Wisconsin, Michigan, Illinois, and Indiana. The data come from settlement-era Public Land Survey (PLS) data (ca. 0.8-km resolution) of trees recorded by land surveyors. The surveyor notes have been transcribed, cleaned, and processed to estimate stem density, basal area, and biomass at individual points. The point-level data are aggregated within 8 km grid cells and smoothed using a generalized additive statistical model that accounts for zero-inflated continuous data and provides approximate Bayesian uncertainty estimates. The statistical modeling smooths out sharp spatial features (likely arising from statistical noise) within areas smaller than about 200 km2. Based on this modeling, presettlement Midwestern landscapes supported multiple dominant species, vegetation types, forest types, and ecological formations. The prairies, oak savannas, and forests each had distinctive structures and spatial distributions across the domain. Forest structure varied from savanna (averaging 27 Mg/ha biomass) to northern hardwood (104 Mg/ha) and mesic southern forests (211 Mg/ha). The presettlement forests were neither unbroken and massively-statured nor dominated by young forests constantly structured by broad-scale disturbances such as fire, drought, insect outbreaks, or hurricanes. Most forests were structurally between modern second growth and old growth. We expect the data product to be useful as a baseline for investigating how forest ecosystems have changed in response to the last several centuries of climate change and intensive Euro-American land use and as a calibration dataset for paleoecological proxy-based reconstructions of forest composition and structure for earlier time periods. The data products (including raw and smoothed estimates at the 8-km scale) are available at the LTER Network Data Portal as version 1.0.

Highlights

Terrestrial vegetation in midwestern North America changed drastically at the time of EuroAmerican settlement [1,2]
We present gridded 8 km-resolution data products of the estimated stem density, basal area, and biomass of tree taxa at Euro-American settlement of the midwestern United States during the middle to late 19th century for the states of Minnesota, Wisconsin, Michigan, Illinois, and Indiana
The data come from settlement-era Public Land Survey (PLS) data of trees recorded by land surveyors

Summary

Introduction

Terrestrial vegetation in midwestern North America changed drastically at the time of EuroAmerican settlement [1,2]. The midwestern United States was the location of a major ecological transition between the grasslands of the Great Plains and the forests of eastern and northern North America [3,4,5]. These grasslands have mostly been replaced by agriculture or pastoral land use, except in areas of prairie conservation or restoration. We quantify the structure (distribution and size) of forests, woodlands, and grasslands across the Midwest using statistical methods that provide the first statistically robust estimates of stem density, basal area, and biomass preceding 19th century land clearance

Methods

Results

Conclusion