Trajectory from beech and oak forests to eastern broadleaf forests in Indiana, USA

Brice B Hanberry

doi:10.1186/s13717-018-0155-3

Abstract

BackgroundHistorical forests (circa 1799 to 1846) of Indiana were predominantly composed of American beech (25% of all trees) and upland oaks (27% of all trees). I compared historical forest composition, using studies of smaller areas to approximate composition for uncommon species or genera (< 4.5% of all trees) and forest types, to current forest composition and forest types in Indiana. I also compiled published historical density estimates from small studies and estimated current density for the state.ResultsCurrent forests are diverse with an even composition of many eastern broadleaf species. In addition to upland oaks, which decreased to 13% of all trees, only sugar maple currently comprises greater than 10% of all trees. Other increasing species were yellow-poplar, red maple, black cherry, and eastern redcedar. Eastern redcedar increased from no presence to one of the most abundant ten species (≥ 3.5% of composition), similarly to the pine genus, becoming more common currently than American beech. Beech or oak or beech-oak forest types (≥ 24% of all trees) became eastern broadleaf forests, with no dominant species, and black cherry, red maple, and eastern redcedar forest types now occurred. Estimates of historical oak or beech forests ranged from 28 trees per hectare to 175 trees per hectare, which probably represent savannas and woodlands. Current mean density of Indiana forests is 385 trees per hectare, ranging from 180 trees per hectare to 450 trees per hectare. These forests likely contain dense layers of woody vegetation, filling the midstory and replacing herbaceous vegetation in the ground layer.ConclusionHistorically dominant beech and oak forests in the eastern United States have transitioned to an alternative state of closed eastern broadleaf forests due to uncontrolled establishment of many tree species.

Highlights

Historical forests of the central eastern US were about 55% oaks, out of all trees (Hanberry and Nowacki 2016)
Because oaks typically occurred in low-density open forests of savannas and woodlands, rather than more dense forests, the total area covered by oak forests in the central eastern US probably was greater than 55% (Hanberry and Abrams 2018)
As for minor to trace species, there seemed to be some flux in small-statured trees, from hornbeam, hophornbeam, and dogwood to sassafras, but representation of small tree species in surveys may be incomplete primarily because smaller tree species may not have been selected by historical tree surveyors (Hanberry et al 2012)

Summary

Introduction

Historical forests of the central eastern US were about 55% oaks, out of all trees (Hanberry and Nowacki 2016). Other major forest types may have been dominated primarily by American beech or pines, which comprised about 5 to 6% of trees in this region (Hanberry and Nowacki 2016). Other genera of maple and hickory were about as common, they typically are uniformly distributed as minor components across the region rather than dominant as a forest type. Potzger et al (1956) used the approximately 214,500 surveyed trees to describe Indiana’s forests in bar graph format, presenting for 1000 townships only the five most common species or genera of American beech (Fagus grandifolia), oaks (primarily Quercus alba, Q. prinus, Q. rubra, Q. velutina), sugar maple (Acer saccharum), ash (Fraxinus americana, F. quadrangulata), and hickories (primarily Carya glabra, Carya ovata). I compiled published historical density estimates from small studies and estimated current density for the state

Methods

Results

Discussion

Conclusion