31 research outputs found
Effects of soil process formalisms and forcing factors on simulated organic carbon depth-distributions in soils.
No full textInternational audienceSoil organic carbon (OC) sequestration (i.e. the capture and long-term storage of atmospheric CO2) is being considered as a possible solution to mitigate climate change, notably through land use change (conversion of cropped land into pasture) and conservation agricultural practices (reduced tillage). Subsoil horizons (from 30 cm to 1 m) contribute to ca. half the total amount of soil OC, and the slow dynamics of deep OC as well as the relationships between the OC depth distribution and changes in land use and tillage practices still need to be modelled. We developed a fully modular, mechanistic OC depth distribution model, named OC-VGEN. This model includes OC dynamics, plant development, transfer of water, gas and heat, mixing by bioturbation and tillage as processes and climate and land use as boundary conditions. OC-VGEN allowed us to test the impact of 1) different numerical representations of root depth distribution, decomposition coefficients and bioturbation; 2) evolution of forcing factors such as land use, agricultural practices and climate on OC depth distribution at the century scale. We used the model to simulate decadal to century time scale experiments in Luvisols with different land uses (pasture and crop) and tillage practices (conventional and reduced) as well as projection scenarios of climate and land use at the horizon of 2100. We showed that, among the different tested formalisms/parametrizations: 1) the sensitivity of the simulated OC depth distribution to the tested numerical representations depended on the considered land use; 2) different numerical representations may accurately fit past soil OC evolution while leading to different OC stock predictions when tested for future forcing conditions (change of land use, tillage practice or climate)
Which benefits in the use of a modeling platform : the VSoil example
No full textIn the environmental community the need for coupling the models and the associated knowledges emerged recently. The development of a coupling tool or of a modeling platform is mainly driven by the necessity to reate models accounting for multiple processes and to take into account the feed back between these processes. Models focusing on a restricted number of processes exist and thus the coupling of these numerical tools appeared as an efficient and rapid mean to fill up the identified gaps. Several tools have been proposed : OMS3 (David et al. 2013) ; CSDMS framework (Peckham et al. 2013) ; the Open MI project developed within the frame of European Community (Open MI, 2011). However, what we should expect from a modeling platform could be more ambitious than only coupling existing numerical codes. We believe that we need to share easily not only our numerical representations but also the attached knowledges. We need to rapidly and easily develop complex models to have tools to bring responses to current issues on soil functioning and soil evolution within the frame of global change. We also need to share in a common frame our visions of soil functioning at various scales, one the one hand to strengthen our collaborations, and, on the other hand, to make them visible by the other communities working on environmental issues. The presentation will briefly present the VSoil platform. The platform is able to manipulate concepts and numerical representations of these processes. The tool helps in assembling modules to create a model and automatically generates an executable code and a GUI. Potentialities of the tool will be illustrated on few selected cases
