Two Hundred Years of Forest Change: Effects of Urbanization on Tree Species Composition and Structure

Despite their importance, the dynamics of urban floras are not well understood and quantitative historical data are rare. The current study used three data sets for trees in Indianapolis/Marion County, Indiana, U.S., to document change over 200 years to the original beech-maple forest and to examine future implications of contemporary tree planting efforts in light of these changes. Data on tree composition and size collected before significant settlement in the early 1800s are compared with recent surveys of trees in remnant natural areas and with trees found on city streets and rights-of-way. All the species recorded in historical surveys are still present in either remnant natural area forests or among city street trees, but frequencies and sizes have changed and many additional species are now present. Comparison of the composition of the original forest with current remnants shows a 95% decline of American beech (Fagus grandifolia), the most common species in presettlement forests. Sugar maple (Acer saccharum) has more than doubled in number. Silver maple (Acer saccharinum) is the most important street tree, with eight species of non-native broadleaf trees among the most common on city streets, along with evergreen gymnosperms that are not documented in the presettlement flora. Data for contemporary tree planting efforts in the city show a focus on native species that targets replacement of species that have declined in frequency, especially oaks, in proportions that should be sustainable. Patterns reported here are likely representative of those in many forested areas undergoing land conversion and development, so the findings apply to many cities