Changes in demography and carrying capacity of green ash and black ash ten years after emerald ash borer invasion of two ash-dominant forests

• Published in: Forest ecology and management 2021-08, Vol.494, p.119335, Article 119335
• Main Authors: Siegert, Nathan W., Engelken, Patrick J., McCullough, Deborah G.
• Format: Article
• Language: English
• Subjects: Agrilus planipennis; Ash demography; Ash regeneration; EAB carrying capacity; Fraxinus nigra; Fraxinus pennsylvanica; Invasive forest pest
• ISSN: 0378-1127; 1872-7042
• DOI: 10.1016/j.foreco.2021.119335

•We quantified changes in ash demography before and after EAB-induced tree mortality.•Green ash and black ash basal area was reduced by more than 94% in post-invasion forests.•25–30% of EAB-killed green ash had surviving stump sprouts while black ash had none.•Newly germinated seedlings were absent as seed-producing ash trees had been extirpated.•Recruitment of ash saplings in aftermath forests is likely to be limited by endemic EAB populations. Quantifying changes in ash (Fraxinus spp.) demography and emerald ash borer (EAB; Agrilus planipennis) carrying capacity in forested ecosystems is essential for understanding impacts of this invader and projecting future species composition in aftermath forests in North America. We inventoried green ash (F. pennsylvanica) and black ash (F. nigra) trees in two ash-dominated Michigan forests invaded by EAB, estimated phloem area, and potential EAB adult production before tree mortality occurred in 2007 and 2008. We re-inventoried both areas approximately a decade later to assess post-invasion ash demographics and EAB carrying capacity. Ash distribution by size class initially followed a negative exponential function. In the Pre-EAB inventories, small trees (2.5–13 cm dbh) accounted for more than 70% of the stems but comprised less than 20% of the ash phloem. Mid-sized trees (26–42 cm dbh) represented 13 cm dbh were dead and EAB carrying capacity was reduced by 94% and 99% in the two areas. Live stump sprouts were present on 25–30% of EAB-killed green ash trees but were absent on dead black ash trees. Ash sapling and recruit density varied within and between forests, but newly germinated ash seedlings were absent. Whether green or black ash will function as overstory species in post-invasion forests in North America may be jeopardized by the near extirpation of seed sources and endemic EAB populations likely to limit recruitment of ash saplings and seedlings.