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Research article - Peer-reviewed, 2022

Interactive effects of drought and edge exposure on old-growth forest understory species

Koelemeijer, Irena A.; Ehrlen, Johan; Jonsson, Mari; De Frenne, Pieter; Berg, Peter; Andersson, Jenny; Weibull, Henrik; Hylander, Kristoffer


Context Both climatic extremes and land-use change constitute severe threats to biodiversity, but their interactive effects remain poorly understood. In forest ecosystems, the effects of climatic extremes can be exacerbated at forest edges. Objectives We explored the hypothesis that an extreme summer drought reduced the richness and coverage of old-growth forest species, particularly in forest patches with high edge exposure. Methods Using a high-resolution spatially explicit precipitation dataset, we could detect variability in drought intensity during the summer drought of 2018. We selected 60 old-growth boreal forest patches in central Sweden that differed in their level of drought intensity and amount of edge exposure. The year after the drought, we surveyed red-listed and old-growth forest indicator species of vascular plants, lichens and bryophytes. We assessed if species richness, composition, and coverage were related to drought intensity, edge exposure, and their interaction. Results Species richness was negatively related to drought intensity in forest patches with a high edge exposure, but not in patches with less edge exposure. Patterns differed among organism groups and were strongest for cyanolichens, epiphytes associated with high-pH bark, and species occurring on convex substrates such as trees and logs. Conclusions Our results show that the effects of an extreme climatic event on forest species can vary strongly across a landscape. Edge exposed old-growth forest patches are more at risk under extreme climatic events than those in continuous forests. This suggest that maintaining buffer zones around forest patches with high conservation values should be an important conservation measure.


Edge effects; Extreme weather; Fragmentation; Land-use; Microclimate; Woodland key habitats

Published in

Landscape Ecology
2022, volume: 37, number: 7, pages: 1839-1853
Publisher: SPRINGER

Authors' information

Koelemeijer, Irena A.
Stockholm University
Ehrlen, Johan
Stockholm University
Swedish University of Agricultural Sciences, Swedish Species Information Centre
De Frenne, Pieter
Ghent University
Berg, Peter
Swedish Meteorological and Hydrological Institute
Andersson, Jenny
Naturcentrum AB
Weibull, Henrik
Naturcentrum AB
Hylander, Kristoffer
Stockholm University

Sustainable Development Goals

SDG15 Life on land

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