White Ash tree
The White Ash tree, or Fraxinus americana, is a type of ash tree that is native to eastern and central North America.
Description
White ash trees grow between 60 to 100 feet tall on average, with a 2 to 3 foot trunk diameter. It is the largest of the ash trees found in North America. The leaves are opposite, and have between 5 and 9 leaflets. The bark ranges in color from yellow-brown to light grey and has deep furrows. White ash trees are dioecious, meaning there are separate male and female trees.
Distribution
The White ash tree is found only in the central and eastern parts of North America, ranging as far north as Nova Scotia, south into northern Florida, and west into the upper areas of Texas and parts of Iowa. Habitats include floodplain woodlands, upland woodlands, shaded gravelly seeps, high riverbanks, limestone glades, and in city parks.
Ecological Importance
White Ash hosts many species of insects, which feed on parts of the tree. At least 280 arthropods rely on White Ash trees as a source of food and shelter. Additionally, White Ash trees provide habitat and food for many vertebrates, such as squirrels, deer, various birds, and mice. Ash trees also play an important role in nutrient and water cycling in forests.
Threats
Due to the accidental introduction of the Emerald Ash Borer, white ash trees have seen a significant decrease in population, and this has led to many adverse ecological effects. Widespread ash mortality severely alters forest habitats and dynamics. This causes loss of habitat and food for many organisms, including 44 species of arthropods that feed exclusively on ash trees.
Additionally, loss of ash trees, and therefore an increase in sunlight on forest floors, may cause an increase in the spread of invasive species, such as honeysuckle, multiflora rose, and autumn olive.
Widespread ash mortality also can alter soil pH, mineral concentrations, and soil moisture levels, affecting nutrient and water availability for nearby trees and other organisms living in the soil.
Another threat to the White Ash Tree is the ascomycete fungus disease, Hymenoscyphus fraxineus. It causes crown dieback and leaf loss in Ash trees resulting in a 69% mortality rate in the wild [2]. Due to the probable immunity of Ash trees of Asian origin, the disease can first be traced back to Europe. It is spread by wind transportation of spores and nursery infestations. When infected, lesions can be found through the stems, branches and xylem of the tree [3]. As of right now there are no effective management strategies to resolve this issue [9].
References
[1] Ash Tree Update 2017 (U.S. National Park Service). (n.d.). . https://www.nps.gov/articles/ash-tree-update.htm.
[2] Estimating mortality rates of European ash (Fraxinus excelsior) under the ash dieback (Hymenoscyphus fraxineus) epidemic - Coker - 2019 - PLANTS, PEOPLE, PLANET - Wiley Online Library. (n.d.). . https://nph.onlinelibrary.wiley.com/doi/10.1002/ppp3.11.
[3] ETH - Forest Pathology and Dendrology. (n.d.). . https://web.archive.org/web/20121105034253/http://www.forestpathology.ethz.ch/research/Chalara_fraxinea/index_EN.
[4] Fraxinus americana - Plant Finder. (n.d.). . https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=a867.
[5] Fraxinus americana (American Ash, White Ash) | North Carolina Extension Gardener Plant Toolbox. (n.d.). . https://plants.ces.ncsu.edu/plants/fraxinus-americana/.
[6] Maine proposes Emerald Ash Borer quarantine rules. (n.d.). . https://www.wabi.tv/2021/03/17/maine-proposes-emerald-ash-borer-quarantine-rules/.
[7] White Ash. (n.d.). . https://naturalresources.extension.iastate.edu/forestry/iowa_trees/trees/white_ash.html.
[8] White Ash (Fraxinus americana). (n.d.). . https://www.illinoiswildflowers.info/trees/plants/white_ash.html.
[9] Are Europe’s ash trees finished? | New Scientist. (n.d.). . https://www.newscientist.com/article/dn22449-are-europes-ash-trees-finished/?ignored=irrelevant.