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Research article - Peer-reviewed, 2017

Annual climate variation modifies nitrogen induced carbon accumulation of Pinus sylvestris forests

Lim, Hyungwoo; Oren, Ram; Linder, Sune; From, Fredrik; Nordin, Annika; Fahlvik, Nils; Lundmark, Tomas; Nasholm, Torgny

Abstract

We report results from long-term simulated external nitrogen (N) input experiments in three northern Pinus sylvestris forests, two of moderately high and one of moderately low productivity, assessing effects on annual net primary production (NPP) of woody mass and its interannual variation in response to variability in weather conditions. A sigmoidal response of wood NPP to external N inputs was observed in the both higher and lower productivity stands, reaching a maximum of similar to 65% enhancement regardless of the native site productivity, saturating at an external N input of 4-5 g N . m(-2) . yr(-1). The rate of increase in wood NPP and the N response efficiency (REN, increase in wood NPP per external N input) were maximized at an external N input of similar to 3 gN . m(-2) (.) yr(-1), regardless of site productivity. The maximum REN was greater in the higher productivity than the lower productivity stand (similar to 20 vs. similar to 14 g C/g N). The N-induced enhancement of wood NPP and its REN were, however, markedly contingent on climatic variables. In both of the higher and lower productivity stands, wood NPP increased with growing season precipitation (P), but only up to similar to 400 mm. The sensitivity of the response to P increased with increasing external N inputs. Increasing growing season temperature (T) somewhat increased the N-induced drought effect, whereas decreasing T reduced the drought effect. These responses of wood NPP infused a large temporal variation to REN, making the use of a fixed value unadvisable. Based on these results, we suggest that regional climate conditions and future climate scenarios should be considered when modeling carbon sequestration in response to N deposition in boreal P. sylvestris, and possibly other forests.

Keywords

carbon sequestration; climate change; Heureka model; nitrogen deposition; nitrogen gradient; nitrogen use efficiency; precipitation; Scots pine; Pinus sylvestris; temperature

Published in

Ecological Applications
2017, Volume: 27, number: 6, pages: 1838-1851