Ash dieback, soil and deer browsing influence natural regeneration of European ash (Fraxinus excelsior L.)

European ash (Fraxinus excelsior L.) dieback affects both overstory trees and natural regeneration. The decline of ash caused by severe crown defoliation and branch mortality has a high impact on ash natural regeneration. The site factors affecting the disease symptoms vary significantly and are not...

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Bibliographic Details
Published in:The Science of the total environment 2021-01, Vol.752, p.141787-141787, Article 141787
Main Authors: Turczański, Krzysztof, Dyderski, Marcin K., Rutkowski, Paweł
Format: Article
Language:English
Subjects:
CaCO3
Herbivory
Hymenoscyphus fraxineus
Saplings
Soil pH
Tree mortality
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Summary:European ash (Fraxinus excelsior L.) dieback affects both overstory trees and natural regeneration. The decline of ash caused by severe crown defoliation and branch mortality has a high impact on ash natural regeneration. The site factors affecting the disease symptoms vary significantly and are not fully understood. Hence, we aimed to assess the joined effects of soil fertility and moisture (expressed by soil pH, CaCO3 content, and summer groundwater table level), herbivory, and health conditions connected with Hymenoscyphus fraxineus (T. Kowalski) Baral, Queloz, and Hosoya infestation on natural regeneration of F. excelsior. We examined 32 ash stands in Western Poland across soil fertility gradient. We established randomly selected circular plots (400 m2) in forests with ≥60% of ash in overstory species composition. We assessed natural regeneration density, the proportion of browsed trees, and trees damaged by ash dieback using generalized mixed-effects models. We found a higher proportion of damaged trees in neutral and base soils than in acid soils. Moreover, we found a low proportion of damaged trees in sites with low groundwater table levels. High CaCO3 content decreased the proportion of browsed trees, similarly as high shrub cover. The density of F. excelsior natural regeneration depended on groundwater table level, canopy cover, and proportion of damaged trees. We also found a positive relationship between density and deer browsing. The factor responsible for the higher infestation of saplings (low groundwater table level) also influenced natural regeneration density. This way, our study revealed how soil properties influence ash natural regeneration directly and indirectly. We showed that ash dieback will have a more severe impact on ash regeneration in ash typical sites. This is essential for predicting forest recovery and the ability to resilience after disturbances caused by H. fraxineus. Joined effects of ash dieback, soil pH, and CaCO3 content, together with soil moisture, as well as deer browsing, affect ash regeneration. [Display omitted] •Patterns of ash dieback in ash natural regeneration are weakly understood.•We assessed ash natural regeneration density and health in ash-dominated forests.•Soil pH and moisture influence ash regeneration mortality.•Ash regeneration seems to be more vulnerable to ash dieback in ash typical sites.
ISSN:0048-9697
1879-1026
DOI:10.1016/j.scitotenv.2020.141787