Using regional forest nutrition data to inform urban tree management in the northeastern United States

Abstract Managing tree health in urban environments is complicated due to the disconnect that exists between novel environmental conditions created by urbanization and those under which tree species evolved. Soils influence tree health and growth, but optimal nutrient and pH recommendations are often informed by agricultural and horticultural norms which do not typically include norms for forest tree species. At the Arnold Arboretum in Boston, Massachusetts, USA, we investigated the relationships between tree health, foliar chemistry, and soil chemistry for three native forest tree species (Acer saccharum, Quercus alba, and Tsuga canadensis) located throughout the arboretum. We compared these ranges and relationships to data collected from trees of the same species growing in forested areas throughout the northeastern United States. For all species, the distributions of most foliar nutrient concentrations were similar in the arboretum and across the region. However, foliar potassium (K) concentrations were lower at the arboretum than in reference datasets. Soil pH was higher at the arboretum than most forest soils in the region, potentially a result of liming and irrigation with city water. Concentrations of soil and foliar magnesium were also high at the arboretum. Potassium deficiency could result from the blocking of K uptake by magnesium or limited K availability due to forest floor loss. In addition, there is some evidence that manganese is at low to deficient levels. These results show the value of comparing chemical conditions between urban tree populations with trees in natural forests in nearby rural settings to identify potential areas of concern and inform soil management strategies.