Changes of vegetation in coniferous monocultures in the context of conversion to mixed forests in 30 years - Implications for biodiversity restoration

Alexander Seliger; Christian Ammer; Holger Kreft; Stefan Zerbe

doi:10.1016/j.jenvman.2023.118199

Changes of vegetation in coniferous monocultures in the context of conversion to mixed forests in 30 years - Implications for biodiversity restoration

J Environ Manage. 2023 Oct 1:343:118199. doi: 10.1016/j.jenvman.2023.118199. Epub 2023 May 25.

Authors

Alexander Seliger¹, Christian Ammer², Holger Kreft³, Stefan Zerbe⁴

Affiliations

¹ Free University of Bozen-Bolzano, Faculty of Agricultural, Environmental and Food Sciences, Bolzano, Italy; University of Göttingen, Department of Silviculture and Forest Ecology of the Temperate Zones, Faculty of Forest Sciences and Forest Ecology, Göttingen, Germany. Electronic address: alexander.seliger@unibz.it.
² University of Göttingen, Department of Silviculture and Forest Ecology of the Temperate Zones, Faculty of Forest Sciences and Forest Ecology, Göttingen, Germany.
³ University of Göttingen, Department of Biodiversity, Macroecology and Biogeography, Faculty of Forest Sciences and Forest Ecology, Göttingen, Germany.
⁴ Free University of Bozen-Bolzano, Faculty of Agricultural, Environmental and Food Sciences, Bolzano, Italy.

PMID: 37244102
DOI: 10.1016/j.jenvman.2023.118199

Abstract

The understorey vegetation of temperate forests harbours a major proportion of terrestrial biodiversity and fulfills an important role in ecosystem functioning. Over the past decades, temperate forest understoreys were found to change in species diversity and composition due to several anthropogenic and natural drivers. Currently, the conversion and restoration of even-aged coniferous monocultures into more diverse and mixed broad-leaved forests are major objectives of sustainable forest management in Central Europe. This forest conversion alters understorey communities and abiotic site conditions but the underlying patterns and processes are not yet fully understood. Therefore, we investigated changes in the Bavarian Spessart mountains in southwest Germany, where we re-sampled 108 semi-permanent plots from four different coniferous stand types (i.e., Norway spruce, Scots pine, Douglas fir, European larch) about 30 years after the initial assessment. On these plots, we recorded understorey vegetation and forest structure, and derived abiotic site conditions based on ecological indicator values of understorey vegetation, followed by multivariate analysis. We found changes in plant communities that point towards a decrease of soil acidity and a "thermophilization" of forest understoreys. Understorey species richness remained constant, while understorey's Shannon and Simpson diversity increased. The observed changes in forest structure explained the temporal shifts in understorey species composition. The understorey species composition did not experience a significant floristic homogenization since the 1990s. However, plant communities exhibited a reduction in species characteristic of coniferous forests and a simultaneous increase in species associated with broad-leaved forests. The increase of specialist species (closed forests and open sites) may have compensated for the detected decrease in generalist species. We conclude that the forest conversion towards mixed broad-leaved forest in the Spessart mountains of the past decades might have masked homogenization trends that are increasingly reported from Central European forest understoreys.

Keywords: Forest biodiversity; Forest management; Plant community change; Re-survey; Species richness and diversity; Understorey species composition.

MeSH terms

Biodiversity
Ecosystem*
Forests
Plants
Tracheophyta*
Trees