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WP9 models

Based on the models, skills and experience available among the partners in WP9, three models have been identified and selected. These are COUP, LPJ-GUESS and JULES.

Model selection

The model toolbox contains information about three biogeochemical models. These were chosen among many possible options based on the following criteria:

• Flexibility in terms of ecosystems and drivers
• Documentation (manuals, user friendliness, access and references)
• Complementarity (the three components of the model toolbox should ideally complement each other in terms of processes, drivers, ecosystems etc.)
• Competences among the WP partners

Other models exist that could have fitted in as well, but no models have been identified which would have clear advantages over the ones chosen. Some ecosystem specific models for forests, grasses or agriculture might have advantages for those specific ecosystems, but would loose on the flexibility.

Parameter inputs

The models require a range of driving variables as well as characterising parameters and validation parameters. The driving variables are mostly climatic variables and management/treatments, which can be substantial, but which are required by any biogeochemical model, and they are more or less identical across the models.

Site characteristics and soil and plant parameters differ across models. These include quite many of which not all may be available at each site. Site specific solutions will have to be taken to obtain the parameters needed. The toolbox will provide guidelines for this.

Validation parameters will typically depend on the scientific question raised in a given project, and should therefore not be difficult to get from a given project. The toolbox will provide guidelines to more elaborate validation parameters.

Strengths

The different models are generally quite flexible with respect to terrestrial ecosystem types, they operate at slightly different scales and have different strengths. In combination this means that the model toolbox will provide models that together will provide useful model tools to cover most relevant ecosystem types and land uses, address key questions related to biogeochemical cycling and address questions at different time and spatial scales. Key strengths are:

• COUP – plot scale, soil hydrology & energy, C and N
• LPJ-GUESS – Plot-regional scale, vegetation dynamics, atmospheric feedback
• JULES – Landscape scale, hydrologic and carbon flows and feedbacks

Weaknesses

None of the models address other elements (like P and nutrients) or acidity.

The models are under constant development involving inclusion of new processes and/or improved descriptions. For the use within ExpeER none of the models will need specific technical/scientific developments, since they broadly cover the ecosystem types and drivers employed within ExpeER.