Street and park trees of Boston: a comparison of urban forest structure

Abstract

This paper evaluates the structure of street and park trees in Boston's neighborhoods of Roxbury and North Dorchester. The general hypothesis is that forest structures of two components of the public urban forest, street and park trees, are significantly different such that they may warrant different policy and management strategies. Data from an inventory of the neighborhoods in 1988–1989 include species, diameter at breast height, and condition of each tree. Descriptive variables calculated from the data include species diversity, size class diversity, percentage of the tress that are in good condition, and species importance lists. From the descriptive variables, size class diversity is greater for street than for park trees. Species diversity and percentage of trees in good condition are greater for park than for street trees. Results from chi-square analyses on tree condition, size class categories, and size class categories for Acer platanoides and Quercus rubra for Condition Class 3 all reject the null hypothesis that street and park tree populations are distributed similarly. A comparison of the importance lists that include the species that collectively make up 75% of all individuals and total basal area shows that there are only seven species required to reach that percentage for street trees, and 14 for park trees. At the 75% level, all species that make up at least 5% of all individuals and total basal area are included. Of the seven tree species on the importance list for street trees, only one is a member of the presettlement forest and all are tolerant of urban environmental stress. For park trees, over half of the 14 species on the importance list are members of the presettlement forest, and at least seven are tolerant of urban environmental stress. The results indicate that street and park trees are distinct populations within urban forests, and hence the processes acting to create these two components of the urban forest resource may also differ.