A new hope: Condition of young stands suggests natural recovery of European ash in Northern Europe

Abstract

The dieback has severely affected both overstory trees and natural regeneration of European ash (Fraxinus excelsior). The diseased mature trees have mostly been harvested, and ash has regenerated only naturally. The density and health condition of the naturally regenerated ash were assessed in 69 young stands in post-clear- or sanitary clear-felled mixed stands scattered across Latvia. On average, 4665 ashes per ha were accounted, of which 59 % were healthy, 36 % were infected to varying degrees, and 4 % had died recently. The density and health condition of young ash were similar to the prior survey in 2015, suggesting some stability of ash in the ecosystem with relatively rich natural regeneration. Nevertheless, the age/size-related susceptibility to disease has shifted, as the damage increased for the saplings, while the health condition, hence vigour and growth of the larger ashes improved considerably, suggesting a potentially successful regeneration pulse. Still, stand properties affected the health of ash. The health condition was positively related to the overall tree density, and negatively related to the density of ash, suggesting that removal of the infected ashes by selective thinning could enhance the vitality of the stands. The current stand composition suggests regeneration of mostly mixed broadleaved stands with ash admixture, and implying a gradual recovery of European ash.