Modification of the RothC model for simulation of Soil Organic Carbon dynamics in rangelands under humid temperate climate

1. Modification of the RothC model for simulation of Soil Organic Carbon
dynamics in rangelands under humid temperate climate
Asma Jebari1*, Jorge Álvaro-Fuentes2, María Almagro Bonmatí1, Agustín del Prado1,3
1 Basque Centre for Climate Change (BC3) 2 Soil and Water Dpt, Estacion Experimental de Aula Dei (EEAD), Spanish National Research Council (CSIC) 3Basque Centre for Applied
Mathematics (BCAM)
April – June 2019
asma.jebari@bc3research.org
INTRODUCTION AND OBJECTIVES
Predicting Soil Organic Carbon (SOC) dynamics on
grasslands has become of major interest, as grasslands
(particularly temperate grasslands) are one of the most
widespread vegetation types worldwide, and the most
important stores of SOC.
Modelling is one important pathway to achieve this goal and
to have better knowledge of grazing effect and of animal, soil
and plant interactions.
Our main aim is to develop a new version of the RothC
(Coleman and Jenkinson., 1996) as an important SOC model,
taking into account residues quality and grazing effect.
RESULTS
MATERIALS AND METHODS
CONCLUSIONS
The BC3 is supported by the Basque Government through the BERC 2018-2021
program and by Spanish Ministry of Economy and Competitiveness MINECO
through María de Maeztu excellence accreditation MDM-2017-0714. Asma
Jebari is financed by the the Fundación Cándido de Iturriaga y Mª de
Dañobeitia. Agustin del Prado is financed by the programme Ramon y Cajal
from the Spanish Ministry of Economy, Industry and Competitiveness (RYC-
2017-22143).
REFERENCES
RothC model Modification
Plant residue quality and its variability
 C in the Neutral Detergent Fiber (NDF) (i.e., holocellulose and the
lignin fractions) was used as a proxy for resistant plant material
(RPM).
 C in Neutral Detergent Soluble (NDS) was used as a proxy for
Decomposable plant material (DPM).
Diversity of exogenous organic matter
Exogenous organic matter partition in the RothC model was based on
its biochemical composition.
Animal treading effect
Poaching damage is a common problem in areas with higher annual
precipitation. It has an effect on reducing pasture production.
The poaching submodel was developed referring to experimental
studies under temperate humid climate.
Soil Water Saturation
We included the water contents up to saturation in the soil water
function of RothC referring to the water content between field capacity
and water saturation, as our study area is susceptible to soil water
saturated conditions.
Simulation results
The modified model was able to detect C sequestration rate in
the seminatural intensive “Laqueuille site” and gave comparable
results to soil inventories (Carbon sink of 0.7 Mg C ha-1 yr-1
compared to measured value of 0.8 Mg C ha-1 yr-1 at 20 cm depth)
as in Herfurth (2015).
• Herfurth, Damien. Impact des pratiques de gestion sur le stockage du Carbone dans le sol des
écosystèmes prairiaux. Sciences agricoles. Université Blaise Pascal - Clermont-Ferrand II, 2015.
• Klumpp, K., T. Tallec, N. Guix, and J.F. Soussana. 2011. Long-term impacts of agricultural practices
and climatic variability on carbon storage in a permanent pasture. Glob. Chang. Biol. 17(12): 3534–
3545.
Model validation
Study site (published data)
Seminatural intensive grassland in Auvergne, ‘Laqueuille’, France
(45°38′N, 2° 44′E).
The management is a continuous grazing from May to end of October
without additional feed supply, with an annual stocking rate of 1.1 LSU
ha-1 and an annual average Nitrogen fertilization of 210 kg N ha-1.
(Klumpp et al., 2011)
The modifications made in this study allowed a better
presentation of the grassland systems and improved the
model performance.
 We suggest to integrate the modified SOC model with a
Nitrogen model to simulate both Carbon and Nitrogen
dynamics under temperate and humid grasslands
ecosystems.
SOC stocks at 20 cm depth in an intensive grassland of Laqueuille site in France
during the period 2004-2012 using the default and modified versions of the
RothC model