Assessing the Hazard of Emerald Ash Borer and Other Exotic Stressors to Community Forests

Abstract

Exotic stressors such as emerald ash borer are an increasing concern to many communities across North America. One means of assessing the hazard these stressors may represent to a community’s publicly managed trees is through an inventory of their street trees. The South Dakota Division of Resource Conservation and Forestry conducted street tree inventories in selected communities across the state and, from these data, have placed communities into stability categories based on the percentage of full stocking that each genera represents within the street tree population. The majority of surveyed communities are in the low stability category as a result of the dominance of green ash in their street tree populations.

Street Tree Diversity in Three Northeastern U.S. States

“…Visual uniformity can be accomplished while also satisfying the need for species diversity by grouping trees that are visually compatible based on size, shape, branching density, and foliage texture (Bassuk et al undated). Better understanding of diversity importance can be achieved through increased education (Polakowski et al 2011) and perhaps through a change in terminology by stressing the reduction of species and genera overuse (Ball et al 2007).…”

“…Street tree diversity also has been assessed at broader geographic levels, such as a region or state. Lesser (1996) assessed street tree diversity in southern California based on inventory data from 21 cities, Ball et al (2007) assessed street tree diversity in South Dakota, U.S., based on inventory data from 34 communities statewide, and Raupp et al (2006) assessed street tree diversity in the temperate zone of eastern North America based on inventory data from 12 cities and one college campus.…”

“…Santamour proposed as a general rule that no tree species should comprise more than 10%, no tree genus should comprise more than 20%, and no tree family should comprise more than 30% of a municipality's street tree population. Thus, Sanders (1981) found Norway maple (Acer platanoides) to comprise 37.5% of all street trees in Syracuse, New York, U.S.; Lesser (1996) found American sweetgum (Liquidambar styraciflua) to comprise 14.27% of all street trees in 21 southern California cities; and Ball et al (2007) found ashes (Fraxinus spp.) to comprise 36.3% of all street trees in 34 South Dakota communities.…”

Tools for Staging and Managing Emerald Ash Borer in the Urban Forest

“…Ash trees contribute significantly to the canopy of urban forests, with 38 million trees estimated to be present in eastern North America (Kovacs et al 2010). While ash species account for between 20% and 30% of the urban forest in many cities, it is not uncommon for cities in some regions of the United States (e.g., Colorado and Iowa) to have an ash component of >50% (Raupp et al 2006;Ball et al 2007;Sydnor et al 2007;Sydnor et al 2011). Thus, the spread of EAB threatens a substantial portion of the urban forest and will cost North American cities well over USD $10 billion to manage (Kovacs et al 2010;McKenny et al 2012).…”

Table_1.XLSX

“…In the temperate northeastern US, Acer species dominate the urban forest (Cowett and Bassuk, 2017), and recent plantings in this region continue to feature species in the genera Quercus, Syringa, and Prunus despite their current abundance (Doroski et al, 2020). Similarly, Fraxinus pennsylvanica Marshall comprised 35.3% of the total street tree population in communities in South Dakota -a state with a continental climate (Ball et al, 2007). In subtropical Tampa, Florida, only 10 of the 109 inventoried species made up 63% of Tampa's inland urban forest (Landry et al, 2018).…”