Carbon-nitrogen interactions in European forests and semi-natural vegetation - Part 1: Fluxes and budgets of carbon, nitrogen and greenhouse gases from ecosystem monitoring and modelling
Journal article, 2020

The impact of atmospheric reactive nitrogen (N-r) deposition on carbon (C) sequestration in soils and biomass of unfertilized, natural, semi-natural and forest ecosystems has been much debated. Many previous results of this dC/dN response were based on changes in carbon stocks from periodical soil and ecosystem inventories, associated with estimates of N-r deposition obtained from large-scale chemical transport models. This study and a companion paper (Flechard et al., 2020) strive to reduce uncertainties of N effects on C sequestration by linking multi-annual gross and net ecosystem productivity estimates from 40 eddy covariance flux towers across Europe to local measurement-based estimates of dry and wet N-r deposition from a dedicated collocated monitoring network. To identify possible ecological drivers and processes affecting the interplay between C and N-r inputs and losses, these data were also combined with in situ flux measurements of NO, N2O and CH4 fluxes; soil NO3- leaching sampling; and results of soil incubation experiments for N and greenhouse gas (GHG) emissions, as well as surveys of available data from online databases and from the literature, together with forest ecosystem (BAS-FOR) modelling. Multi-year averages of net ecosystem productivity (NEP) in forests ranged from -70 to 826 gCm(-2) yr(-1) at total wet + dry inorganic N-r deposition rates (N-dep) of 0.3 to 4.3 gNm(-2) yr(-1) and from -4 to 361 g Cm-2 yr(-1) at N-dep rates of 0.1 to 3.1 gNm(-2) yr(-1) in short semi-natural vegetation (moorlands, wetlands and unfertilized extensively managed grasslands). The GHG budgets of the forests were strongly dominated by CO2 exchange, while CH4 and N2O exchange comprised a larger proportion of the GHG balance in short semi-natural vegetation. Uncertainties in elemental budgets were much larger for nitrogen than carbon, especially at sites with elevated N-dep where N-r leaching losses were also very large, and compounded by the lack of reliable data on organic nitrogen and N-2 losses by denitrification. Nitrogen losses in the form of NO, N2O and especially NO3- were on average 27%(range 6 %-54 %) of N-dep at sites with N-dep < 1 gNm(-2) yr(-1) versus 65% (range 35 %-85 %) for N-dep > 3 gNm(-2) yr(-1). Such large levels of N-r loss likely indicate that different stages of N saturation occurred at a number of sites. The joint analysis of the C and N budgets provided further hints that N saturation could be detected in altered patterns of forest growth. Net ecosystem productivity increased with N-r deposition up to 2-2.5 gNm(-2) yr(-1), with large scatter associated with a wide range in carbon sequestration efficiency (CSE, defined as the NEP/GPP ratio). At elevated N-dep levels (> 2.5 gNm(-2) yr(-1)), where inorganic N-r losses were also increasingly large, NEP levelled off and then decreased. The apparent increase in NEP at low to intermediate N-dep levels was partly the result of geographical cross-correlations between N-dep and climate, indicating that the actual mean dC/dN response at individual sites was significantly lower than would be suggested by a simple, straightforward regression of NEP vs. N-dep.

Author

Chris R. Flechard

Inst Natl Rech Agr Alimentat & Environm INRAE

Andreas Ibrom

Technical University of Denmark (DTU)

Ute M. Skiba

UK CEH

Wim de Vries

Wageningen University and Research

Marcel van Oijen

UK CEH

David R. Cameron

UK CEH

Nancy B. Dise

UK CEH

Janne F. J. Korhonen

University of Helsinki

Nina Buchmann

Swiss Federal Institute of Technology in Zürich (ETH)

Arnaud Legout

Inst Natl Rech Agr Alimentat & Environm INRAE

David Simpson

Chalmers, Space, Earth and Environment, Microwave and Optical Remote Sensing

Maria J. Sanz

University of the Basque Country (UPV/EHU)

Marc Aubinet

University of Liège

Denis Loustau

Inst Natl Rech Agr Alimentat & Environm INRAE

Leonardo Montagnani

Free University of Bozen-Bolzano

Autonomous Prov Bolzano

Johan Neirynck

Research Institute for Nature and Forest, Brussels

Ivan A. Janssens

University of Antwerp

Mari Pihlatie

University of Helsinki

Ralf Kiese

Karlsruhe Institute of Technology (KIT)

Jan Siemens

Justus Liebig University Giessen

Andre-Jean Francez

University of Rennes 1

Juergen Augustin

Leibniz Ctr Agr Landscape Res ZALF

Andrej Varlagin

Russian Academy of Sciences

Janusz Olejnik

Poznan University of Life Sciences

AS CR

Radoslaw Juszczak

Poznan University of Life Sciences

Mika Aurela

Finnish Meteorological Institute (FMI)

Daniel Berveiller

University of Paris-Sud

Bogdan H. Chojnicki

Poznan University of Life Sciences

Ulrich Dammgen

Weststr 5

Nicolas Delpierre

University of Paris-Sud

Vesna Djuricic

Meteorol & Hydrol Serv

Julia Drewer

UK CEH

Eric Dufrene

University of Paris-Sud

Werner Eugster

Swiss Federal Institute of Technology in Zürich (ETH)

Yannick Fauvel

Inst Natl Rech Agr Alimentat & Environm INRAE

David Fowler

UK CEH

Arnoud Frumau

Netherlands Organisation for Applied Scientific Research (TNO)

Andre Granier

Inst Natl Rech Agr Alimentat & Environm INRAE

Patrick Gross

Inst Natl Rech Agr Alimentat & Environm INRAE

Yannick Hamon

Inst Natl Rech Agr Alimentat & Environm INRAE

Carole Helfter

UK CEH

Arjan Hensen

Netherlands Organisation for Applied Scientific Research (TNO)

Laszlo Horvath

Greengrass - Atmospheric Environment Expert Ltd. Fellowship

Barbara Kitzler

Fed Res & Training Ctr Forests Nat Hazards & Land

Bart Kruijt

Wageningen University and Research

Werner L. Kutsch

Integrated Carbon Observat Syst ICOS ERIC Head Of

Raquel Lobo-do-Vale

University of Lisbon

Annalea Lohila

Finnish Meteorological Institute (FMI)

University of Helsinki

Bernard Longdoz

Gembloux Agrobio Tech

Marek

Acad Sci

Giorgio Matteucci

National Research Council of Italy (CNR)

Marta Mitosinkova

Slovak Hydrometeorological Institute

Virginie Moreaux

Université Grenoble Alpes

Inst Natl Rech Agr Alimentat & Environm INRAE

Albrecht Neftel

NRE

Jean-Marc Ourcival

University of Montpellier

Kim Pilegaard

Technical University of Denmark (DTU)

Gabriel Pita

Univ Tecn Lisboa

Francisco Sanz

Fdn CEAM

Jan K. Schjoerring

University of Copenhagen

Maria-Teresa Sebastia

Forest Sci & Technol Ctr Catalonia CTFC

Universidad De Lleida

Y. Sim Tang

UK CEH

Hilde Uggerud

Norwegian Institute for Air Research (NILU)

Marek Urbaniak

Poznan University of Life Sciences

Netty van Dijk

UK CEH

Timo Vesala

University of Helsinki

Sonja Vidic

Meteorol & Hydrol Serv

Caroline Vincke

Universite catholique de Louvain

Tamas Weidinger

Eötvös Loránd University (ELTE)

Sophie Zechmeister-Boltenstern

University of Natural Resources and Life Sciences

Klaus Butterbach-Bah

Karlsruhe Institute of Technology (KIT)

Eiko Nemitz

UK CEH

Mark A. Sutton

UK CEH

Biogeosciences

1726-4170 (ISSN) 1726-4189 (eISSN)

Vol. 17 6 1583-1620

Subject Categories

Environmental Sciences related to Agriculture and Land-use

Physical Geography

Environmental Sciences

DOI

10.5194/bg-17-1583-2020

More information

Latest update

1/9/2021 9