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Research article - Peer-reviewed, 2021

Release of retained oaks in Norway spruce plantations. A 10-year perspective on oak vitality, spruce wood production and ground vegetation

Lariviere, Delphine; Holmstrom, Emma; Brunet, Jorg; Weslien, Jan;

Abstract

This study explores the decade-long effects of release cutting around old retained oaks (Quercus robur L.) in a Norway spruce (Picea abies L. Karst) stand that was 33 year old when thinned. The impacts on both nature conservation values and spruce wood production were evaluated in a randomized block design. To release oaks from competition, stems of Norway spruce were cut around 33 oaks, in three different treatments: high release (HR), medium release (MR) and no release (NR). Trees within a circular sample plot (15 m radius from the oak) were measured at time of treatment and 10 years after. The treatment effects on stand development, oak vitality and understory vegetation were evaluated after ten years, using tree diameter, height measurements, oak crown and tree structure estimates as well as ground vegetation surveys. Release cutting did not impact spruce production within the sample plot, and given that there were no other obvious sources of spruce suppression in the stand, we speculate that release cutting has little to no impact at the stand scale. Oak crowns in the control plots (NR) became smaller after ten years, while the crowns expanded and colonized the gap in the release treatments. Simultaneously, the amount of dead wood in the crown increased among oaks in the control treatment, indicating dieback. Cover and species richness of vascular plants in the understory were significantly higher in the HR and MR treatments compared to NR. These results suggest that the creation of relatively wide gaps (greater than 2 m) around retained oak crowns is one efficient approach to maintain their conservation values in a spruce dominated stand on a longer time frame. This will allow oaks to expand their crowns, increase their vitality and increase species richness and diversity of plants under the canopy. The economic loss of creating large gaps instead of no gaps may be negligible since the overall spruce production was not affected within 15 m of each oak.

Keywords

Release cutting; Gap dynamics; Quercus robur; Tree retention; Legacy tree; Biodiversity; Ground vegetation; Picea abies

Published in

Forest Ecology and Management

2021, volume: 480, article number: 118670
Publisher: ELSEVIER

Authors' information

Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre
Forestry Research Institute of Sweden, Skogforsk
Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre
Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre
Weslien, Jan
Forestry Research Institute of Sweden, Skogforsk

UKÄ Subject classification

Forest Science

Publication Identifiers

DOI: https://doi.org/10.1016/j.foreco.2020.118670

URI (permanent link to this page)

https://res.slu.se/id/publ/110246