Quantifying Carbon Storage in Black Ash Wetlands Following Emerald Ash Borer and Forest Management

Abstract The impacts of non-native Emerald Ash Borer (EAB) are likely to be most severe in black ash wetlands, possibly requiring preemptive forest management to maintain ecosystem functions such as carbon storage. We used a silvicultural experiment in northern Minnesota to evaluate how EAB-induced mortality and preemptive management affect total ecosystem carbon storage and the distribution of carbon among ecosystem pools. Treatments included tree girdling to emulate EAB-induced tree mortality, clearcutting, 20% canopy removal with group selection and an undisturbed control. Ash trees ( Fraxinus spp.) in the control black ash wetlands stored 116.7 (± 5.3) Mg C ha −1 , and live tree carbon storage increased by 1.8 (± 0.12) Mg C ha −1 yr −1 over the study period. Twelve years after treatment, total ecosystem carbon was lower in all treatments relative to the control and lowest in clearcuts. In the emulated-EAB treatment, representing a do-nothing scenario, total ecosystem carbon decreased by 22% relative to the control, with 71.6 (± 4.7) Mg C ha −1 remaining in deadwood pools where continued decomposition will lead to further carbon storage loss. Understory carbon increased in clearcuts following treatment, but only a small fraction was associated with potential canopy-replacement species. Soil carbon storage was highly variable, with no significant differences among treatments. Our results demonstrate that both EAB-induced mortality and preemptive management substantially alter carbon storage in black ash wetlands. Further management aimed at maintaining forest canopy, particularly through the establishment of non-host tree species, may be necessary to prevent a permanent reduction in regional carbon storage.