Soil C:N stoichiometry controls carbon sink partitioning between above-ground tree biomass and soil organic matter in high fertility forests

iForest - Biogeosciences and Forestry. 2015;8(1):195-206 DOI 10.3832/ifor1196-008


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Journal Title: iForest - Biogeosciences and Forestry

ISSN: 1971-7458 (Online)

Publisher: Italian Society of Silviculture and Forest Ecology (SISEF)

Society/Institution: SISEF

LCC Subject Category: Agriculture: Forestry

Country of publisher: Italy

Language of fulltext: English

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Alberti G (Department of Agriculture and Environmental Sciences, University of Udine, Udine (Italy))

Vicca S (Research Group of Plant and Vegetation Ecology, Department of Biology, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk (Belgium))

Inglima I (Department of Environmental Science, Second University of Naples, Caserta (Italy))

Belelli-Marchesini L (Department for Innovation in Biological, Agro-food and Forest systems, University of Tuscia, Viterbo (Italy))

Genesio L (Institute of Biometeorology, National Research Council of Italy - CNR/IBIMET, Firenze (Italy))

Miglietta F (Institute of Biometeorology, National Research Council of Italy - CNR/IBIMET, Firenze (Italy))

Marjanovic H (Croatian Forest Research Institute, Jastrebarsko (Croatia))

Martinez C (Institute of Biometeorology, National Research Council of Italy - CNR/IBIMET, Firenze (Italy))

Matteucci G (Institute for Agriculture and Forestry System in the Mediterranean, National Research Council of Italy - CNR/ISAFOM, Rende, CS (Italy))

D’Andrea E (Institute of Agroenvironmental and Forest Biology, National Research Council of Italy - CNR/IBAF, Monterotondo, RM (Italy))

Peressotti A (Department of Agriculture and Environmental Sciences, University of Udine, Udine (Italy))

Petrella F (Istituto per le Piante da Legno e l’Ambiente - IPLA, Turin (Italy))

Rodeghiero M (Department of Sustainable Agro-ecosystems and Bioresources, Research and Innovation Centre, Fondazione Edmund Mach (FEM), v. E. Mach 1, I-38010 San Michele all’Adige (Italy))

Cotrufo Maria F (Department of Soil and Crop Science, Colorado State University, Fort Collins, Colorado (USA))


Peer review

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Instructions for authors

Time From Submission to Publication: 40 weeks


Abstract | Full Text

The release of organic compounds from roots is a key process influencing soil carbon (C) dynamics and nutrient availability in terrestrial ecosystems. Through this process, plants stimulate microbial activity and soil organic matter (SOM) mineralization thus releasing nitrogen (N) that sustains gross and net primary production (GPP and NPP, respectively). Root inputs also contribute to SOM formation. In this study, we quantified the annual net root-derived C input to soil (Net-Croot) across six high fertility forests using an in-growth core isotope technique. On the basis of Net-Croot, wood and coarse root biomass changes, and eddy covariance data, we quantified net belowground C sequestration. Belowground C accumulation and GPP were inversely related to soil C:N, but not to climate or stand age. Soil C content and C:N were also related to soil texture. At these high fertility sites, biomass growth did not change with soil C:N; however, biomass growth-to-GPP ratio significantly increased with increasing soil C:N. This was true for both our six forest sites and for another 23 high fertility sites selected at a global scale. We suggest that, at high fertility sites, plant N demand interacts with soil C:N stoichiometry and microbial activity, resulting in higher allocation of C to above ground tree biomass with increasing soil C:N ratio. When C:N is high, microbes have a low C use efficiency, respire more of the fresh C inputs by roots and prime SOM decomposition, thereby increasing N availability for tree uptake. Soil C sequestration would therefore decrease, whereas the extra N released during SOM decomposition can promote tree growth and ecosystem C sink allocation in aboveground biomass. Conversely, C is sequestered in soil when low soil C:N promotes microbial C use efficiency and new SOM formation and stabilization on clay particles.