Resolving uncertainties in predictive equations for urban tree crown characteristics of the southeastern United States: Local and general equations for common and widespread species

Abstract

2Urban forest research and management requires improved methods for quantifying ecosystem structure and function. Regional equations for urban tree crown width and height can accordingly improve predictions of urban tree structure. Using a large regional dataset with 12 locations in the southeastern US, we developed diameter-based equations for 97 urban tree species. Whereas previously published urban equations have almost exclusively been developed with one location on public or commercial land, our data included both public and private land uses. For 5 widespread, common urban tree species (Acer rubrum, Cornus florida, Pinus taeda, Quercus nigra and Lagerstroemia spp.), we also assessed the inclusion of additional variables such as crown light exposure, land cover, basal area, and location. Overall, height and crown width models were improved when including additional predictors, although competition and location effects varied by species. Study city was a significant predictor of tree height in all species except C. florida, and a significant predictor of crown width for all species except C. florida and Q. nigra. This indicates that anthropogenically-influenced variation among cities can lead to significant differences in both tree form and structure and that future model development should utilize data encompassing multiple cities. Our predictive equations for urban tree crown characteristics provide an improved method for planning, management, and estimating the provision of ecosystem services to improve quality of life in cities.3

Trees on Buildings: A Tree Selection Framework Based on Industry Best Practice

“…Plant proximity, particularly the space between trees, is also a vital consideration, as close proximity will result in an undesirable level of shading, affecting growth and form as plants seek more light, resulting in undesirable forms and proportions [65]. On the other hand, increasing the distance between plants will increase solar heating of the soil, possibly reducing plant health and green roof aesthetics as mentioned by the participants.…”

Urban tree monitoring: a resource guide

“…Projected ecosystem services are also sensitive to changes in tree growth (Ko et al 2015b, Widney et al 2016), yet there is very little empirical data about tree growth in urban environments (Roman et al 2015). Urban tree allometry-the sizing relationships of trees (e.g., equations to estimate height, crown dimensions, and biomass from trunk size)-is another essential component of ecosystem services and population projection models (Blood et al 2016, McHale et al 2009, McPherson et al 2016, Troxel et al 2013. Generating more tree mortality, growth, and allometry data-across cities, programs, species, and site conditions-is critical to improve model accuracy.…”