Forest Compositional Changes after a Decade of Emerald Ash Borer

Jordan M Marshall

doi:10.3390/f11090949

Abstract

Emerald ash borer is an invasive pest in North American forests. Ecological impacts of ash mortality from emerald ash borer are wide-ranging, including shifts in insect communities and wildlife behavior. Additionally, loss of ash from forests may have important implications regarding plant succession. Surveys of overstory, midstory, and understory trees within forests in northeastern Indiana, Lower Peninsula of Michigan, and northwestern Ohio were conducted to quantify the change in forest composition over a 10 year period. Interpolation of ash dominance illustrated inversion of live and dead ash values between 2007 and 2017. Even though more than 83% of overstory live ash basal area was lost across the study area, green ash was the most abundant midstory and understory species representing regeneration. Additionally, loss of ash from many of the sites resulted in compositional changes that were greater than merely the subtraction of ash. Due to the relatively large number of forest types with which ash species are associated, loss of ash will have broad ecological consequences, including on community composition.

Highlights

Introduced in the 1990s from Asia, emerald ash borer (Agrilus planipennis Fairmaire) has become a well-established insect pest in North American forests [1,2]
Even though more than 83% of overstory live ash basal area was lost across the study area, green ash was the most abundant midstory and understory species representing regeneration
There was a reduction in mean live ash basal area from 3.29 to 0.54 m2 /ha across the entire study area, with an increase in mean dead ash basal area from 0.23 to 4.91 m2 /ha

Summary

Introduction

Introduced in the 1990s from Asia, emerald ash borer (Agrilus planipennis Fairmaire) has become a well-established insect pest in North American forests [1,2]. Efforts have been made to improve biological and silvicultural control methods, as well as urban focused chemical control techniques, e.g., [4,5,6] Those improvements have had little impact on emerald ash borer, as evidenced by its continued spread and infestation, as well as continued ash mortality. Ecological impacts of emerald ash borer in infested forests are potentially broad, ranging from changes in wildlife behavior and insect abundances to successional trajectories and nutrient cycling [7,8,9]. The breadth of these impacts is an indication of the relative importance of ash species within North American forests. Densities of ash and other species within forests are variable and will likely relate to overstory composition [11,12]

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