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Research article - Peer-reviewed, 2020

Coppicing improves the growth response of short-rotation hybrid aspen to elevated atmospheric humidity

Tullus, Arvo; Rosenvald, Katrin; Lutter, Reimo; Kaasik, Ants; Kupper, Priit; Sellin, Arne


Aspens are fast-growing clonal trees with a wide circumboreal distribution range, suitable for the production of pulp and bioenergy. The adaptability of aspen short-rotation coppice systems to climate change has rarely been investigated. For a large part of aspens' northern range, climate models predict an increase in precipitation and, consequently, in atmospheric humidity. Our aim was to clarify the long-term effect of elevated air humidity on vegetative reproduction capacity and dynamics of above-ground growth and size structure in aspen stands. We analysed tree growth data from two consecutive 6-year rotations (a planted and a coppice generation) in experimental short-rotation hybrid aspen (Populus tremula L. x P. tremuloides Michx.) stands in the Free Air Humidity Manipulation (FAHM) experiment in Estonia. In three plots, mean relative air humidity was elevated by 7% and three plots were controls. Across two rotation periods, the humidification effect on tree height and/or stem basal area increment was year-dependent (p < 0.001): negative in 4 years, positive also in 4 years and non-significant in 3 years. Mean basal area of humidified (11.6 +/- 0.8 cm(2)) and control trees (15.0 +/- 1.0 cm(2)) differed significantly (p = 0.035) at the end of the first but not the second rotation period (9.3 +/- 0.9 cm(2) and 9.3 +/- 1.2 cm(2), respectively). Average growth differences levelled out already in the beginning of the second rotation, suggesting that some root-level acclimation must have taken place. The annual size-growth relationships (SGR) indicated a more size-symmetric growth in humidified (SGR = 1.00 +/- 0.05) and a size-asymmetric growth (SGR = 1.12 +/- 0.04) in control stands, implying a greater role of root-competition in humidified stands. In humidified stands, the growth of re-sprouting trees was more strongly determined by parent tree size, indicating a stronger carry-over of size hierarchy. The tree height diversity fluctuated more in control stands, where mortality was higher, especially after dry years. To summarise, short- and long-term responses of hybrid aspen to elevated air humidity varied, emphasizing the importance of long-term climate manipulations with trees. Generally, hybrid aspen short-rotation coppice forests showed promising acclimation capacity with future more humid climate predicted for northern latitudes.


Aspen coppice; Climate change; Forest acclimation; Intraspecific competition; Populus; Stand structure

Published in

Forest Ecology and Management
2020, volume: 459, article number: 117825

Authors' information

Tullus, Arvo
University of Tartu
Rosenvald, Katrin
University of Tartu
Lutter, Reimo
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Lutter, Reimo
Estonian University of Life Sciences
Kaasik, Ants
University of Tartu
Kupper, Priit
University of Tartu
Sellin, Arne
University of Tartu

Sustainable Development Goals

SDG13 Climate action

UKÄ Subject classification

Forest Science

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