Workpackage Ecosystem CO2 exchange modelling


Workpackage manager: Dr. Alessandro CESCATTI & Dr. Georg WOHLFAHRT


Objectives:
The objective of WP 4 is to simulate the annual net ecosystem CO2 exchange (NEE) of mountain ecosystems in order to assess the contribution of various ecosystem components, their interactions and the way these are influenced by land use, and to provide an alternative method for gap filling for annual carbon balance estimates (WP 1).

Methodology / work description:
A multi-layer modelling approach will be followed, dividing both the canopy space and the soil into a finite number of discrete layers. The above-ground modules calculate the fluxes of CO2 and energy originating from the canopy phytoelements within the boundaries defined by an arbitrary reference level above the canopy and the soil surface. Radiative transfer, the absorption of momentum, and the turbulent fluxes of CO2 and energy and the respective source/sink strengths will be explicitly resolved for each canopy layer. The below-ground modules calculate soil respiration, the transport of water and heat within the soil and the regulation of stomatal conductance by soil water availability. Model theory will be refined with regard to soil respiration, aiming at a more detailed treatment of the component processes, the exchange processes during snow cover, and stress effects (water and cold stress) on ecosystem physiology. Input data consist of time series for the meteorological forcing variables, and structural/functional parameters describing the state of the soil-vegetation system. Necessary model input data have been gathered largely within the frame of previous projects, additional data will be acquired within the frame of WP 2 and 3, validation data will be contributed by WP 1. The model GrasSVAT 3.2, implemented into a user-friendly software, will be made available to the various partner teams to ensure comparable modelling results.


Deliverables:

  • Development and adaptation of ecosystem SVAT modelling software
  • Parameterised and validated models of NEE for all ecosystems studied
  • Data sets for filling gaps in measured NEE (WP 1)
  • Application of models for a detailed process analysis of NEE, including effects of canopy structure and functional group physiology and of snow cover duration
  • Scenarios of land-use effects on NEE

Milestones:

  • Ecosystem modelling software available
  • Parameterisation of ecosystem models
  • Validation of ecosystem models
  • Data sets for gap filling available (WP 1)
  • Ecosystem process analysis and land-use scenarios