Observed and modelled ecosystem respiration and gross primary production of a grassland in southwestern France
Open Access
- 21 May 2010
- journal article
- research article
- Published by Copernicus GmbH in Biogeosciences (online)
- Vol. 7 (5), 1657-1668
- https://doi.org/10.5194/bg-7-1657-2010
Abstract
In this work, the rich dataset acquired at the SMOSREX experimental site is used to enhance the A-gs version of the Interactions between Soil, Biosphere and Atmosphere (ISBA) model. A simple representation of the soil moisture effect on the ecosystem respiration is implemented in the ISBA-A-gs model. It results in an improvement of the modelled CO2 flux over a grassland in southwestern France. The former temperature-only dependent respiration formulation used in ISBA-A-gs is not able to model the limitation of the respiration under dry conditions. In addition to soil moisture and soil temperature, the only parameter required in this formulation is the ecosystem respiration parameter Re25. It can be estimated by means of eddy covariance measurements of turbulent nighttime CO2 flux (i.e. ecosystem respiration). The resulting correlation between observed and modelled net ecosystem exchange is r2=0.63 with a bias of −2.18 μmol m−2 s−1. It is shown that when CO2 observations are not available, it is possible to use a more complex model, able to represent the heterotrophic respiration and all the components of the autotrophic respiration, to estimate Re25 with similar results. The modelled ecosystem respiration estimates are provided by the Carbon Cycle (CC) version of ISBA (ISBA-CC). ISBA-CC is a version of ISBA able to simulate all the respiration components, whereas ISBA-A-gs uses a single equation for ecosystem respiration. ISBA-A-gs is easier to handle and more convenient than ISBA-CC for the practical use in atmospheric or hydrological models. Surface water and energy flux observations, as well as Gross Primary Production (GPP) estimates, are compared with model outputs. The dependence of GPP to air temperature is investigated. The observed GPP is less sensitive to temperature than the modelled GPP. Finally, the simulations of the ISBA-A-gs model are analysed over a seven year period (2001–2007). Modelled soil moisture and Leaf Area Index (LAI) are confronted with the observed surface and root-zone soil moisture content (m3 m−3), and with LAI estimates derived from surface reflectance measurements.Keywords
This publication has 36 references indexed in Scilit:
- Joint assimilation of surface soil moisture and LAI observations into a land surface modelAgricultural and Forest Meteorology, 2008
- Global mapping of vegetation parameters from POLDER multiangular measurements for studies of surface‐atmosphere interactions: A pragmatic method and its validationJournal of Geophysical Research: Atmospheres, 2002
- Modelling CO2-enrichment effects using an interactive vegetation SVAT schemeAgricultural and Forest Meteorology, 2001
- Heat and water exchanges of fallow land covered with a plant-residue mulch layer: a modelling study using the three year MUREX data setJournal of Hydrology, 2001
- Investigating soil and atmospheric plant water stress using physiological and micrometeorological dataAgricultural and Forest Meteorology, 2000
- Soil CO2 efflux in a beech forest: dependence on soil temperature and soil water contentAnnals of Forest Science, 1999
- The ISBA land surface parameterisation schemeGlobal and Planetary Change, 1996
- Inclusion of Gravitational Drainage in a Land Surface Scheme Based on the Force-Restore MethodJournal of Applied Meteorology and Climatology, 1996
- Local variations of ecosystem functions in Mediterranean evergreen oak woodlandAnnals of Forest Science, 1996
- The temperature dependence of soil organic matter decomposition, and the effect of global warming on soil organic C storageSoil Biology and Biochemistry, 1995