Using Structural Measures to Compare Twenty-Two U.S. Street Tree Populations

Abstract

Our purpose is to use certain ecological measures, commonly adopted for understanding natural forest populations, to describe and compare street tree populations. Street trees compose only about 10-20 percent of the urban forest, but there are sufficient data on these populations to apply certain measures of structure and to interpret the results. We used inventories from 22 U.S. cities to compare patterns in species and age composition, stocking levels, and growth forms. From this we infer trends toward greater species diversity and smaller tree size; these trends are discussed in terms of their implications for future costs and benefits. Our assessment is that certain measures can illuminate important attributes of the populations, especially when an array of populations is graphically compared.