Regeneration in European beech forests after drought: the effects of microclimate, deadwood and browsing

Dominik Thom; Christian Ammer; Peter Annighöfer; Réka Aszalós; Sebastian Dittrich; Jonas Hagge; William S Keeton; Bence Kovacs; Ole Krautkrämer; Jörg Müller; Goddert von Oheimb; Rupert Seidl

doi:10.1007/s10342-022-01520-1

Regeneration in European beech forests after drought: the effects of microclimate, deadwood and browsing

Eur J For Res. 2023;142(2):259-273. doi: 10.1007/s10342-022-01520-1. Epub 2022 Dec 8.

Authors

Dominik Thom^{1

2}, Christian Ammer³, Peter Annighöfer⁴, Réka Aszalós⁵, Sebastian Dittrich⁶, Jonas Hagge^{7

8}, William S Keeton^{2

9}, Bence Kovacs⁵, Ole Krautkrämer^{10

11}, Jörg Müller^{12

13}, Goddert von Oheimb⁶, Rupert Seidl^{1

14}

Affiliations

¹ Ecosystem Dynamics and Forest Management Group, School of Life Sciences, Technical University of Munich, Hans-Carl-Von-Carlowitz-Platz 2, 85354 Freising, Germany.
² Gund Institute for Environment, University of Vermont, 617 Main Street, Burlington, VT 05405 USA.
³ Silviculture and Forest Ecology of the Temperate Zones, Faculty of Forest Sciences, University of Göttingen, Büsgenweg 1, 37077 Göttingen, Germany.
⁴ Forestry and Agroforestry Systems Group, School of Life Sciences, Technical University of Munich, Hans-Carl-Von-Carlowitz-Platz 2, 85354 Freising, Germany.
⁵ Centre for Ecological Research, Institute of Ecology and Botany, Alkotmány Út 2-4, Vácrátót, 2163 Hungary.
⁶ Institute of General Ecology and Environmental Protection, Department of Forest Sciences, Technische Universität Dresden, Pienner Straße 7, 01737 Tharandt, Germany.
⁷ Forest Nature Conservation, Northwest German Forest Research Institute, Prof.-Oelkers-Str. 6, 34346 Hann. Münden, Germany.
⁸ Forest Nature Conservation, Faculty of Forest Sciences, Georg-August-University Göttingen, Büsgenweg 3, 37077 Göttingen, Germany.
⁹ Rubenstein School of Environment and Natural Resources, University of Vermont, Burlington, VT 05405 USA.
¹⁰ Animal Ecology, Department of Ecology, Faculty of Biology, Philipps-University of Marburg, Karl-Von-Frisch-Straße 8, 35043 Marburg, Germany.
¹¹ LPV, Thüringer Wald E. V., Rennsteigstraße 18, 98673 Eisfeld, OT Friedrichshöhe Germany.
¹² Ecological Field Station Fabrikschleichach, Department of Animal Ecology and Tropical Biology, University of Würzburg, Glashüttenstraße 5, 96181 Rauhenebrach, Germany.
¹³ Bavarian Forest National Park, Freyunger Strasse 2, 94481 Grafenau, Germany.
¹⁴ Berchtesgaden National Park, Doktorberg 6, 83471 Berchtesgaden, Germany.

Abstract

With progressing climate change, increasing weather extremes will endanger tree regeneration. Canopy openings provide light for tree establishment, but also reduce the microclimatic buffering effect of forests. Thus, disturbances can have both positive and negative impacts on tree regeneration. In 2015, three years before an extreme drought episode hit Central Europe, we established a manipulation experiment with a factorial block design in European beech (Fagus sylvatica L.)-dominated forests. At five sites located in southeastern Germany, we conducted three censuses of tree regeneration after implementing two different canopy disturbances (aggregated and distributed canopy openings), and four deadwood treatments (retaining downed, standing, downed + standing deadwood and removing all deadwood), as well as in one untreated control plot. In addition, we measured understory light levels and recorded local air temperature and humidity over five years. We (i) tested the effects of experimental disturbance and deadwood treatments on regeneration and (ii) identified the drivers of regeneration density as well as seedling species and structural diversity. Regeneration density increased over time. Aggregated canopy openings supported species and structural diversity, but reduced regeneration density. Tree regeneration was positively associated with understory light levels, while maximum vapor pressure deficit influenced tree regeneration negatively. Deadwood and browsing impacts on regeneration varied and were inconclusive. Our study indicates that despite the drought episode regeneration in beech-dominated forests persisted under moderately disturbed canopies. However, the positive effect of increased light availability on tree regeneration might have been offset by harsher microclimate after canopies have been disturbed.

Supplementary information: The online version contains supplementary material available at 10.1007/s10342-022-01520-1.

Keywords: Seedlings; Species diversity; Structural diversity; Tree establishment; Understory.