Impact of Agrillus planipennis on above ground carbon storage and tree growth rates

Background/Question/Methods

Agrillus planipennis (EAB) is an invasive pest that has been causing the death and loss of ash (Fraxinus spp.) populations in deciduous forests of the eastern United States.  EAB is harmful in the larval stage where it feeds on the phloem of the host ash trees and impedes the flow of nutrients.  It is estimated that ash represents approximately 2.5% of carbon storage mass in eastern deciduous forests, and the loss of the ash could have a significant effect on forest composition and tree growth rates.  This study looks at the change in above ground carbon storage among the species remaining after the death of ash in various forest plots located at sites in the eastern deciduous forests that are participating in the EREN Permanent Forest Plot Project. Growth rates are determined by measuring tree diameters and calculating the biomass of the trees in pre-determined 100 m² plots from five forest preserves, and comparing values from data collected annually from 2012 to 2014.  It is predicted that in sites impacted with EAB, the non-ash tree species, including Acer saccharum and Ulmus americana, will exhibit faster growth and carbon storage rates than sites without EAB because of the decreased competition for nutrients, water, and light.   

Results/Conclusions Initial results from plots located in northwest Ohio, where EAB killed nearly all ash trees by 2013, indicate that the loss of ash has not allowed for an increase in growth rates of Acer saccharum. In the single plot completely without ash, Acer saccharum had an average change in diameter of 0.26 cm per year during the period from 2012-2014.  In five plots with standing dead ash, the average change in diameter of Acer saccharum was 0.24 cm per year. The plot without ash did not contain Ulmus americana, and growth rates could not be compared to plots unaffected by EAB and ash death.  The data will be compared to data from other forest locations in the EREN (Ecological Research as Education Network) Permanent Forest Plot Project, with more detailed analysis accounting for different levels of ash prior to EAB infestation.