Skip to main content
Research article - Peer-reviewed, 2022

Long-term nitrogen addition raises the annual carbon sink of a boreal forest to a new steady-state

Zhao, Peng; Chi, Jinshu; Nilsson, Mats B.; Lofvenius, Mikaell Ottosson; Hogberg, Peter; Jocher, Georg; Lim, Hyungwoo; Makela, Annikki; Marshall, John; Ratcliffe, Joshua; Tian, Xianglin; Nasholm, Torgny; Lundmark, Tomas; Linder, Sune; Peichl, Matthias;

Abstract

The boreal forest is an important global carbon (C) sink. Since low soil nitrogen (N) availability is commonly a key constraint on forest productivity, the prevalent view is that increased N input enhances its C sink-strength. This understanding however relies primarily on observations of increased aboveground tree biomass and soil C stock following N fertilization, whereas empirical data evaluating the effects on the whole ecosystem-scale C balance are lacking. Here we use a unique long-term experiment consisting of paired forest stands with eddy covariance measurements to explore the effect of ecosystem-scale N fertilization on the C balance of a managed boreal pine forest. We find that the annual C uptake (i.e. net ecosystem production, NEP) at the fertilized stand was 16 +/- 2% greater relative to the control stand by the end of the first decade of N addition. Subsequently, the ratio of NEP between the fertilized and control stand remained at a stable level during the following five years with an average NEP to N response of 7 & PLUSMN; 1 g C per g N. Our study reveals that this non-linear response of NEP to long-term N fertilization was the result of a cross-seasonal feedback between the N-induced increases in both growing-season C uptake and subsequent winter C emission. We further find that one decade of N addition altered the sensitivity of ecosystem C fluxes to key environmental drivers resulting in divergent responses to weather patterns. Thus, our study highlights the need to account for ecosystem-scale responses to perturbations to improve our understanding of nitrogen-carbon-climate feedbacks in boreal forests.

Keywords

Boreal forest; Carbon sequestration; Climate change; Eddy covariance; Forest management; Nitrogen fertilization

Published in

Agricultural and Forest Meteorology

2022, volume: 324, article number: 109112
Publisher: ELSEVIER

Authors' information

Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Chi, Jinshu
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Chi, Jinshu
The Hong Kong University of Science and Technology (HKUST)
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Jocher, Georg
Czech Academy of Sciences
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
University of Tartu
Makela, Annikki
University of Helsinki
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Ratcliffe, Joshua L. (Ratcliffe, Joshua)
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Tian, Xianglin
University of Helsinki
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management

UKÄ Subject classification

Climate Research
Forest Science

Publication Identifiers

DOI: https://doi.org/10.1016/j.agrformet.2022.109112

URI (permanent link to this page)

https://res.slu.se/id/publ/119258