Research article - Peer-reviewed, 2021
A carbon-budget approach shows that reduced decomposition causes the nitrogen-induced increase in soil carbon in a boreal forest
Marshall, John D.; Peichl, Matthias; Tarvainen, Lasse; Lim, Hyungwoo; Lundmark, Tomas; Nasholm, Torgny; Oquist, Mats; Linder, SuneAbstract
Nitrogen (N) addition causes rapid accumulation of carbon (C) in the soils of boreal forests. The C accumulation has been attributed to an increase in C supply to the soil, to a decrease in mineralization of organic C to CO2, or some combination of the two. We sought to quantify the proportional causes in a case study in a boreal Scots pine forest with or without annual N addition (at 50-100 kg N ha(-1) yr(-1)). We continuously measured soil-surface CO2 exchange with large chambers (20-m(2)surface area) over three growing seasons and derived flux rates from snowpack CO2 profiles during the winter. Models were used to disaggregate the CO2-exchange data into auto-trophic and heterotrophic components. We also measured litterfall and inferred total belowground carbon flux (TBCF). We observed annual soil C accumulation to be higher by 104 g C m(-2) yr(-1) at the fertilized (F) plot compared to the unfertilized reference (R) stand. Total annual C supply to soil (Aboveground litterfall + TBCF) was not increased by the N addition despite a substantial increase in litterfall (+64 g C m(-2) yr(-1)). Instead the sum decreased slightly, by 52 g C m(-2) yr(-1), because of a larger reduction in TBCF. This reduction in soil C supply led us to conclude that the soil C accumulation was entirely due to inhibited substrate mineralization. We speculate that the nitrogen increased soil C by inhibiting heterotrophy, specifically that portion of heterotrophy that is primed by autotrophic carbon.Keywords
Allocation; Automated chamber system; Belowground partitioning; Lignin; Pinus sylvestris; RespirationPublished in
Forest Ecology and Management2021, volume: 502, article number: 119750
Publisher: ELSEVIER
Authors' information
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Tarvainen, Lasse
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Tarvainen, Lasse
University of Gothenburg
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 Genetics and Plant Physiology
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre
UKÄ Subject classification
Forest Science
Publication Identifiers
DOI: https://doi.org/10.1016/j.foreco.2021.119750
URI (permanent link to this page)
https://res.slu.se/id/publ/114213