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The ForestOAD model has been developed in the VSoil platform. It is a tool to optimise the forestry machinery operations and avoid problems of soil degradation and compaction. ForestOAD is essentially based on an existing water balance model, for which minor simplifications and modifications have been made. One of the objectives is to be able to use weather forecasts to estimate changes in humidity over the coming days. As weather forecasts are updated regularly, it was essential to take them into account and therefore to be able to run the simulations again with a new weather forecast. In this context, the initial situation of the modules must correspond to the state of the variables calculated in a previous run for the start time of the new forecasts. A "STOP'n'RESUME" function has been implemented, which authorises the simulation, saves it at selected times and allows it to be restarted from one of the save dates. This required a number of modifications to be made to the VSoil platform and to the modules that use initial situations. The model also uses pedotransfer functions to calculate hydrodynamic properties. The final decision support model will therefore use databases to obtain the predicted climate and its variability, and soil databases to estimate the hydrodynamic properties. One of VSoil's functionalities is the ability to run sets of simulations using parameter distributions. This capability will provide estimates of the variables of interest and their sensitivity to climate and soil uncertainties.

Details of the work carried out under this theme are presented below.

• Mostafa Moradzadeh (postdoctoral fellow from April 2022 to April 2023)

Mostafa Moradzadeh (INRAE, EMMAH, Avignon) worked on the VSoilForOAD project from April 2022 to April 2023 in replacement of Manon Martin who found a new job (see worked done by Manon below). Mostafa more precisely carried out some sensitivity analysis in order to identify the relative influence of some parameters of the model developed in this project (climatic, soil, vegetation, phenological and mulch parameters, and boundary conditions) on a set of model outputs produced by the module implementing the "soil praticability" process (saturation index, praticability index and drying slope). To do that, two methods implementing the Monte Carlo estimation of the Sobol' indices, named soboljansen and sobolSalt (from "sensitivity" R package, see here), were added in the list of R sensitivity analysis methods available in VSoil.

• Manon Martin (postdoctoral fellow from January 2020 to Mai 2022)

Manon Martin (INRAE, EMMAH, Avignon) started her postdoctoral period in January 2020 as part of the VSoilForOAD project (ADEME project) which aims to develop a prototype of a climate service capable of predicting the practicability of the traffic routes, named skid trails, for logging machinery. This work is a continuation of the development of the ForestOAD model she carried out during her PhD (see below). The objective of Manon's postdoctoral period is to find strategies to simplify the parameterisation of this model and to use easily accessible data. To do so, it is necessary to (i) identify the pedotransfer function (empirical relation allowing to determine soil hydraulic properties that are difficult to measure directly, from simple variables such as granulometry) that is most adapted to forest soils and (ii) evaluate the key parameters for predicting water dynamics of forest soils using a global sensitivity analysis method (calculation of Sobol indices). For this purpose, Manon developed several modules that have been integrated to the ForestOAD model: (1) a Fortran module implementing several pedotransfer functions to be evaluated, (2) a C++ module that implements the "climate" process and reads climatic data from different sources: SAFRAN, Météo-France, ECMWF (European Centre for Medium-Range Weather Forecasts) or local data, (3) a C++ module that implements the "evapotranspiration" process and has the capacity to read hourly PET (potential evapotranspiration) data or calculate PET values from climatic data using the ASCE standardized Penman-Monteith formulation, (4) a Fortran module that implements the "crop development" process and calculates a leaf area index profile (using read or calculated phenological dates) and root lengths, and (5) a C++ module that implements the new created "soil praticability" process and that calculates several soil saturation and soil praticability indexes. Moreover, the Sobol sensitivity analysis method (from "sensitivity" R package, see here) was added in the list of R sensitivity analysis methods available in VSoil in order Manon can run sensitivity analysis with experimental design built with both continuous and discrete parameters (an example of discrete parameter is the origin of climatic data: SAFRAN, Météo-France, ECMWF or local). Finally, a new feature is being developed by the VSoil team to stop and resume a simulation in order Manon can use VSoil to provide real-time water dynamics by coupling weather forecasts and soil-plant characteristics.

• Manon Martin (PhD student from October 2016 to October 2019)

Manon Martin (FCBA technological institute) developed the ForestOAD model during her PhD (October 2016 - October 2019) entitled "Development of an hydrologic model of forest soils compacted partially usable in a situation of sparse datas" (the abstract of the thesis is available here in french and english versions). This model is a tool to optimise the forestry machinery operations and avoid problems of soil degradation and compaction. It is a 1D mechanistic soil transfer model based on the PASTIS model (F. Lafolie. 1991. Modeling water flow, nitrogen transport and root uptake including physical non-equilibrium and optimization of the root water potential. Fertilizer Research, 27:215-231 and A. Findeling, P. Garnier, F. Coppens, F. Lafolie, S. Recous, 2007. Modelling water, carbon and nitrogen dynamics in soil covered with decomposing mulch. EJSS, 58, 196-206) and implemented in the VSoil platform. This model was adapted to the forestry context during her thesis.