Links between soil carbon sequestration, root elongation rate and functional traits in 12 herbaceous species

Mr Lorenzo Rossi1,4, Dr. Zhun Mao1, Dr. Luis Merino-Martin1,2, Dr. Catherine Roumet2, Dr. Florian Fort2, Dr. Hassan Boukcim3, Dr. Nathalie Fromin2, Dr. Alexia Stokes1

1AMAP, INRA, IRD, CIRAD, CNRS, University of Montpellier, 34398, Montpellier, France, 2CEFE, CNRS, Univ Montpellier, Univ Paul Valéry Montpellier 3, EPHE, IRD, , Montpellier, France, 3Valorhiz SAS, 1900 Boulevard de la Lironde, Montferrier-sur-Lez, France, 4University of Cassino, Cassino, Italy

Infrastructures are increasing rapidly, and soils are excavated, and then abandoned or revegetated. With the right type of vegetation, these soils could provide several ecosystem services, such as carbon (C) sequestration, reduced erosion rates and enhanced biodiversity. We investigated C sequestration in soil sown with 12 herbaceous species used to revegetate road embankments in southern France. Species were planted as monocultures in 78 steel boxes (0.7 m width x 0.7 m width x 0.3 m depth), that were inclined at 30° to mimic an embankment (6 replicates for each species + 6 bare soil controls). Three replicates were used for soil C analysis and three were equipped with rhizotrons (0.2×0.3m wide and 0.05m thick), for the study of root dynamics. As soon as the first root was visible in the rhizotron, we scanned every two weeks using a smartphone scanner and analyzed images with SmartRoot software. Roots were classed into fine ‘absorptive’ and thicker ‘transport’ roots depending on their topological order. Root elongation rate (RER) and root length production (RLP) were calculated. After ten months, soil samples were collected for fractioning and measurement of C in: particulate organic matter (CPOM) in the 2000-200 µm fraction, fine POM (CfinePOM) in the 50-200µm coarse silt fraction; CSILT in the 20-50 µm fraction and CSILT+CLAY in the <20 µm fraction. Overall, the total C in soil increased over 10 months under all species, but it was constantly reduced in the CSILT+CLAY fraction. RLP of old roots (>two weeks in rhizotron) and the diameter of absorptive roots were significantly correlated with an increase in CSILT only, where C has a longer residence time compared to the larger particulate fractions. Planting species with the appropriate traits could enhance C sequestration on revegetated land, but a better mechanistic understanding of the relationships between roots and C sequestration into different soil fractions is required.


Biography: Lorenzo Rossi is an agronomist specialized in soil sciences, currently carrying out his Joint Ph.D. between INRA Montpellier and Cassino University. His study focuses on sustainable geotechnical infrastructures and technologies, more specifically he is investigating the potential of embankments to act as active carbon sinks

SOIL ORGANIC MATTER

7th International Symposium
Soil Organic Matter

6 – 11 October 2019

Hilton Adelaide

Adelaide, South Australia

Australia

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