Use of BIOME-BGG to simulate Mediterranean forest carbon stocks

Abstract

BIOME-BGC is a bio-geochemical model capable of estimating the water, carbon and nitrogen fluxes and storages of terrestrial ecosystems. Previous research demonstrated that, after proper calibration of its ecophysiological parameters, the model can reproduce the main processes of Mediterranean forest types. The same investigations, however, indicated a model tendency to overestimate woody biomass accumulation. The current paper aims at modifying BIOME-BGC ecophysiological settings to improve the simulation of the woody compartment in Mediterranean forests. The modified ecophysiological parameter is the whole-plant mortality fraction (WPMF), which directly affects the amount of woody biomass stored. The optimal WPMFs of six main forest types in Tuscany are identified by forcing the model to reproduce the maximum standing volumes found in regional and local forest inventories. The effects of this operation are evaluated by comparing the model outputs produced using the original and modified settings to independent measurements from national forest inventories. The results obtained demonstrate the effectiveness of the modifications introduced and consolidate the methodological basis for extending the use of the modeling strategy to other Mediterranean areas

Assessing most relevant factors to simulate current annual increments of beech forests in Italy

“…Theoretical and operational details can be found in the references mentioned below. BIOME-BGC, after a proper calibration for beech (see Chiesi et al 2011b), is capable of estimating respiration and allocation processes of ecosystems close to equilibrium condition (Churkina et al 2003, Waring & Running 2007). For each study site the model can perform a self-initialization through the so-called spin-up phase, which identifies the initial state variables.…”

“…The SCA for beech is derived from the BIO-ME-BGC settings , Chiesi et al 2011b, while BEF and BWD are 1.36 and 0.61, respectively (Federici et al 2008). The two scalars 2 and 100 are applied to convert CAI from carbon to dry matter and from g m -2 to Mg ha -1…”

“…In particular, BIOME-BGC was applied using the ecophysiological parameters reported by Chiesi et al (2011b), and NPP and CAI were predicted using eqn. 1 and 2.…”

Reply: “Use of BIOME-BGC to simulate Mediterranean forest carbon stocks”

“…We have, however, the impression that he has not fully addressed the objectives of our study (Chiesi et al 2011), as well as the assumptions used. Our investigation, in fact, was not aimed at modifying BIOME-BGC simulation of stand growth, as seemingly asserted by Dr. Eastaugh.…”

Comment on Chiesi et al. (2011): “Use of BIOME-BGC to simulate Mediterranean forest carbon stocks”

“…Recently in these pages Chiesi et al (2011) described the application of the BIO-ME-BGC mechanistic forest growth model to Mediterranean forests in Tuscany, Italy. Their primary conclusions were that the model overestimates standing volumes, but that an empirical adjustment of net primary production (NPP) and a recalibration of the whole annual plant mortality fraction (WPMF) is sufficient to align simulations with observations.…”