Short-term effects of whole-tree harvesting on understory plant species diversity and cover in two Norway spruce sites in southern Norway

ABSTRACT

Effects of clear-cut harvesting on ground vegetation plant species diversity and their cover are investigated at two Norway spruce sites in southern Norway, differing in climate and topography. Experimental plots at these two sites were either harvested conventionally (stem-only harvesting) or whole trees including crowns, twigs and branches were removed (whole-tree harvesting), leaving residue piles on the ground for some months. We compare the number of plant species in different groups and their cover sums before and after harvesting, and between the different treatments, using non-parametric statistical tests. An overall loss of ground vegetation biodiversity is induced by harvesting and there is a shift in cover of dominant species, with negative effects for bryophytes and dwarf shrubs and an increase of graminoid cover. Differences between the two harvesting methods at both sites were mainly due to the residue piles assembled during whole-tree harvesting and the physical damage made during the harvesting of residues in these piles. The presence of the residue piles had a clear negative impact on both species numbers and cover. Pile residue harvesting on unfrozen and snow-free soil caused more damage to the forest floor in the steep terrain at the western site compared to the eastern site.

KEYWORDS:

• Whole-tree harvest
• ground vegetation
• biodiversity
• plant cover

Acknowledgements

We would like to thank T. Eldhuset, K.H. Hanssen and O.J. Kjønaas for cooperation, stimulating discussions and comments to earlier versions of the manuscript, to H. Bratli for contributions to fieldwork, cooperation and other contributions at an early stage of the project, and to several other colleagues who in different ways contributed to the project. Thanks are also due to the dedicated forest owners L. Blakstad (at Tjerne) and L. Istad (at Vindberg) for allowing us to use their forests.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was funded by the Research Council of Norway as part of the project “Ecological consequences of increased biomass removal from forests in Norway” [Ecobrem, project no. 192292]. Additional funding was received from the Norwegian Forest and Landscape Institute and the Bioenergy Innovation Centre CenBio and the Triborn project funded by the Research Council of Norway [project nos. 193817 and 233640], respectively.