Modelling short-term CO2 fluxes and long-term tree growth in temperate forests with ASPECTS

Abstract

The net ecosystem exchange (NEE) of CO 2 between temperate forests and the atmosphere governs both carbon removal from the atmosphere and forest growth. In recent years, many experiments have been conducted to determine temperate forest NEE. These data have been used by forest modellers to better understand the processes that govern CO 2 fluxes, and estimate the evolution of these fluxes under changing environmental conditions. Nevertheless, it is not clear whether models capable of handling short-term processes, which are mostly source-driven, can provide an accurate estimate of long-term forest growth, which is potentially more influenced by sink-and phenology-related processes. To analyse the interactions between short-and long-term processes, we developed the ASPECTS model, which predicts long-term forest growth by integrating, over time, hourly NEE estimates. Validation data consisting of measurements of NEE by eddy-covariance and forest carbon reservoir estimates were obtained from mixed deciduous and evergreen experimental forests located in Belgium. ASPECTS accurately estimated both: (1) the NEE fluxes for several years of data; and (2) the amount of carbon contained in stems, branches, leaves, fine and coarse roots. Our simulations demonstrated that: (1) NEE measurements in Belgian forests are compatible with forest growth over the course of the 20th century; and (2) that forest history and long-term processes need to be considered for accurate simulation of short-term CO 2 fluxes.

The effect of soil water content, soil temperature, soil pH-value and the root mass on soil CO2 efflux – A modified model

“…These models are not useful for forest soils. In contrast forest models (Baldocchi and Wilson, 2001;Janssens et al, 2001;Nakano et al, 2004;Rasse et al, 2001) are often of low use at bare soil or meadows.…”

Fire impact on C and N losses and charcoal production in a scrub oak ecosystem

“…In addition, mechanistic models aiming at predicting C sequestration in 21st-century ecosystems will require multiple-flux information beyond simple quantification of fireinduced CO 2 losses and post-fire C stocks. In order to produce long-term predictions, such models typically require separate estimates of C fluxes from leaves, branches, stems, and soil litter (e.g., Rasse et al 2001). These elements are therefore crucial for modelling fire effects.…”

On uncertainties in carbon flux modelling and remotely sensed data assimilation: The Brasschaat pixel case

“…Finally, as discussed in Verstraeten et al (2006a), C-Fix does not compete with dynamic global vegetation and stand scale models (e.g., Cramer et al, 2001;Rasse et al, 2001;Krinner et al, 2005). It is useful to compare C-Fix with these models, but clearly the added value of C-Fix is its capacity for spatially explicit, regional and global parameter estimation.…”