A vertically discretised canopy description for ORCHIDEE (SVN r2290) and the modifications to the energy, water and carbon fluxes

Abstract

Abstract. Since 70% of global forests are managed and forests impact the global carbon cycle and the energy exchange with the overlying atmosphere, forest management has the potential to mitigate climate change. Yet, none of the land surface models used in Earth system models, and therefore none of today's predictions of future climate, account for the interactions between climate and forest management. We addressed this gap in modelling capability by developing and parametrizing a version of the land surface model ORCHIDEE to simulate the biogeochemical and biophysical effects of forest management. The most significant changes between the new branch called ORCHIDEE-CAN (SVN r2290) and the trunk version of ORCHIDEE (SVN r2243) are the allometric-based allocation of carbon to leaf, root, wood, fruit and reserve pools; the transmittance, absorbance and reflectance of radiation within the canopy; and the vertical discretisation of the energy budget calculations. In addition, conceptual changes towards a~better process representation occurred for the interaction of radiation with snow, the hydraulic architecture of plants, the representation of forest management and a~numerical solution for the photosynthesis formalism of Farquhar, von Caemmerer and Berry. For consistency reasons, these changes were extensively linked throughout the code. Parametrization was revisited after introducing twelve new parameter sets that represent specific tree species or genera rather than a group of unrelated species, as is the case in widely used plant functional types. Performance of the new model was compared against the trunk and validated against independent spatially explicit data for basal area, tree height, canopy strucure, GPP, albedo and evapotranspiration over Europe. For all tested variables ORCHIDEE-CAN outperformed the trunk regarding its ability to reproduce large-scale spatial patterns as well as their inter-annual variability over Europe. Depending on the data stream, ORCHIDEE-CAN had a 67 to 92% chance to reproduce the spatial and temporal variability of the validation data.

A representation of the phosphorus cycle for ORCHIDEE (revision 4520)

“…The major modifications since Krinner et al (2005) are listed in the following: a slightly revised carbon allocation scheme from a recent side branch of ORCHIDEE (Naudts et al, 2015), which avoids the capping of the leaf area index at a predefined value; an explicit representation of mesophylic conductance to CO 2 and omission of direct effects of soil moisture stress on the maximum rate of carboxylation (V cmax ) (Vuichard, unpublished data); and a revised thermodynamic scheme which accounts for the heat transported by liquid water into the soil, in addition to the heat conduction process (Wang et al, 2016).…”

“…Vegetation biomass (carbon, nitrogen, and phosphorus) is separated into leaves, roots, sapwood, heartwood, and shortterm (labile) and long-term storage (reserves) (Zaehle and Friend, 2010;Naudts et al, 2015) (Fig. 1).…”

Numerical Evaluation of JULES Surface Tiling Scheme with High-Resolution Atmospheric Forcing and Land Cover Data

“…However, the spatial configuration of the landscape has significant effects on both the surface energy fluxes and the multi-scale circulations (Oliphant et al 2003;Zhou et al 2011). Vertically discretized land surface modeling enables better estimations of the surface fluxes as well as superior reproductions of their temporal and spatial patterns (Naudts et al 2015).…”

Reconstructing European forest management from 1600 to 2010

“…Maps (1) and (2) were combined by taking the fractions of bare soil, grasses and crops in Europe from P&M. The forests inside Europe from the P&M map were replaced by the more detailed species composition fractions in the Brus et al (2012) map, scaling the sum of the Brus et al (2012) fractions to be equal to the total forested fractions present in the P&M map in Europe. Details about the correspondence of the forest species in Brus et al (2012) and the plant functional types (PFTs) used in the ORCHIDEE land surface model can be found in Naudts et al (2014).…”

“…Hence, to fully understand the impact of the large-scale application of forest management, taking into consideration only the carbon balance is not sufficient. Models need to be developed to examine the effects of forest management on the surface climate (e.g., Naudts et al, 2014). Simulation experiments with these models, driven by historical management reconstructions, can help to better appreciate the impact and legacy of historical forest management on today's climate.…”