Estimating daily forest carbon fluxes using a combination of ground and remotely sensed data

Abstract

Several studies have demonstrated that Monteith's approach can efficiently predict forest gross primary production (GPP), while the modeling of net ecosystem production (NEP) is more critical, requiring the additional simulation of forest respirations. The NEP of different forest ecosystems in Italy was currently simulated by the use of a remote sensing driven parametric model (modified C-Fix) and a biogeochemical model (BIOME-BGC). The outputs of the two models, which simulate forests in quasi-equilibrium conditions, are combined to estimate the carbon fluxes of actual conditions using information regarding the existing woody biomass. The estimates derived from the methodology have been tested against daily reference GPP and NEP data collected through the eddy correlation technique at five study sites in Italy. The first test concerned the theoretical validity of the simulation approach at both annual and daily time scales and was performed using optimal model drivers (i.e., collected or calibrated over the site measurements). Next, the test was repeated to assess the operational applicability of the methodology, which was driven by spatially extended data sets (i.e., data derived from existing wall-to-wall digital maps). A good estimation accuracy was generally obtained for GPP and NEP when using optimal model drivers. The use of spatially extended data sets worsens the accuracy to a varying degree, which is properly characterized. The model drivers with the most influence on the flux modeling strategy are, in increasing order of importance, forest type, soil features, meteorology, and forest woody biomass (growing stock volume).

Correction of a 1 km daily rainfall dataset for modelling forest ecosystem processes in Italy

“…When the dataset is corrected, the annual rainfall rises to ∼730 mm, and the simulated GPP value approaches 1570 g C m −2 year −1 . This value is somewhat higher than those found for Mediterranean macchia on the island of Pianosa (1050 g C m −2 year −1 , Chiesi et al , ) and in western Sardinia (1140 g C m −2 year −1 , Chirici et al , ), both of which have a drier climate.…”

“…When the dataset is corrected, the annual rainfall rises to ∼730 mm, and the simulated GPP value approaches 1570 g C m −2 year −1 . This value is somewhat higher than those found for Mediterranean 298 L. Fibbi et al macchia on the island of Pianosa (1050 g C m −2 year −1 , Chiesi et al, 2011) and in western Sardinia (1140 g C m −2 year −1 , Chirici et al, 2015), both of which have a drier climate. Concerning holm oak, the simulated GPP profiles show quite limited seasonal variations that are typical of a Mediterranean evergreen forest (Figure 6(b)).…”

Optimized Application of Biome‐BGC for Modeling the Daily GPP of Natural Vegetation Over Peninsular Spain

“…The depth indicated in conventional soil maps, referring to the depth to bedrock, cannot be directly used to drive Biome-BGC. This has been experimentally confirmed for several European sites and often leads to use the standard soil depth (100 cm) for the application of Biome-BGC on a regional scale (Chiesi et al, 2016;Chirici et al, 2015). 2.…”

“…This particularly concerns the rooting depth, which directly determines the amount of water available to plants, implying the following relevant considerations: The depth indicated in conventional soil maps, referring to the depth to bedrock, cannot be directly used to drive Biome‐BGC. This has been experimentally confirmed for several European sites and often leads to use the standard soil depth (100 cm) for the application of Biome‐BGC on a regional scale (Chiesi et al, ; Chirici et al, ). Due to their climatic features, Mediterranean areas present a soil water recharge in winter/spring followed by its consumption during summer months (Bolle et al, ). The estimation of soil water storage and its consumption through time is therefore particularly critical in these areas for a correct simulation of water stress impact on vegetation. …”

Carbon fluxes above a deciduous forest in Greece

“…However, in Italy, Chirici et al (2016) found NEE values of about 7.0 t C ha -1 y -1 for a beech and a turkey-oak forest at quite different altitudes, and Tirone et al (2003) mention NEE between -5.47 and -6.60 t C ha -1 y for a Q. ilex forest in Castelporziano. It is also interesting to note that similar high values (on the order of -6 t C ha -1 y -1 ) have been reported for forests in northern Europe (Great Britain, sites 20 and 19 in Fig.…”