Nitrogen deposition is the most important environmental driver of growth of pure, even-aged and managed European forests

• Published in: Forest ecology and management Vol. 458; p. 117762
• Main Authors: Etzold, Sophia, Ferretti, Marco, Reinds, Gert Jan, Solberg, Svein, Gessler, Arthur, Waldner, Peter, Schaub, Marcus, Simpson, David, Benham, Sue, Hansen, Karin, Ingerslev, Morten, Jonard, Mathieu, Karlsson, Per Erik, Lindroos, Antti-Jussi, Marchetto, Aldo, Manninger, Miklos, Meesenburg, Henning, Merilä, Päivi, Nöjd, Pekka, Rautio, Pasi, Sanders, Tanja G.M., Seidling, Walter, Skudnik, Mitja, Thimonier, Anne, Verstraeten, Arne, Vesterdal, Lars, Vejpustkova, Monika, de Vries, Wim
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-02-2020
• Subjects: Air pollution; Climate change; Forest management; ICP Forests; Observational study; Ozone; Statistical modelling; ICP Forests; Climate change; Observational study; Air pollution; Forest management; Ozone; Statistical modelling
• ISSN: 0378-1127; 1872-7042
• DOI: 10.1016/j.foreco.2019.117762

•Stand density and age were strong predictors of European forest growth.•We found direct and indirect impacts of N deposition on forest growth.•Forest growth showed a positive, but in some cases quadratic response to N deposition.•Beech forest growth was significantly reduced at high N deposition levels.•Climate predictors were species-specifically related to European forest growth.•There was limited evidence of an ozone impact on European forest growth.
Changing environmental conditions may substantially interact with site quality and forest stand characteristics, and impact forest growth and carbon sequestration. Understanding the impact of the various drivers of forest growth is therefore critical to predict how forest ecosystems can respond to climate change. We conducted a continental-scale analysis of recent (1995–2010) forest volume increment data (ΔVol, m3 ha−1 yr−1), obtained from ca. 100,000 coniferous and broadleaved trees in 442 even-aged, single-species stands across 23 European countries. We used multivariate statistical approaches, such as mixed effects models and structural equation modelling to investigate how European forest growth respond to changes in 11 predictors, including stand characteristics, climate conditions, air and site quality, as well as their interactions. We found that, despite the large environmental gradients encompassed by the forests examined, stand density and age were key drivers of forest growth. We further detected a positive, in some cases non-linear effect of N deposition, most pronounced for beech forests, with a tipping point at ca. 30 kg N ha−1 yr−1. With the exception of a consistent temperature signal on Norway spruce, climate-related predictors and ground-level ozone showed much less generalized relationships with ΔVol. Our results show that, together with the driving forces exerted by stand density and age, N deposition is at least as important as climate to modulate forest growth at continental scale in Europe, with a potential negative effect at sites with high N deposition.