Representing anthropogenic gross land use change, wood harvest, and forest age dynamics in a global vegetation model ORCHIDEE-MICT v8.4.2

Abstract

Abstract. Land use change (LUC) is among the main anthropogenic disturbances in the global carbon cycle. Here we present the model developments in a global dynamic vegetation model ORCHIDEE-MICT v8.4.2 for a more realistic representation of LUC processes. First, we included gross land use change (primarily shifting cultivation) and forest wood harvest in addition to net land use change. Second, we included sub-grid evenly aged land cohorts to represent secondary forests and to keep track of the transient stage of agricultural lands since LUC. Combination of these two features allows the simulation of shifting cultivation with a rotation length involving mainly secondary forests instead of primary ones. Furthermore, a set of decision rules regarding the land cohorts to be targeted in different LUC processes have been implemented. Idealized site-scale simulation has been performed for miombo woodlands in southern Africa assuming an annual land turnover rate of 5 % grid cell area between forest and cropland. The result shows that the model can correctly represent forest recovery and cohort aging arising from agricultural abandonment. Such a land turnover process, even though without a net change in land cover, yields carbon emissions largely due to the imbalance between the fast release from forest clearing and the slow uptake from agricultural abandonment. The simulation with sub-grid land cohorts gives lower emissions than without, mainly because the cleared secondary forests have a lower biomass carbon stock than the mature forests that are otherwise cleared when sub-grid land cohorts are not considered. Over the region of southern Africa, the model is able to account for changes in different forest cohort areas along with the historical changes in different LUC activities, including regrowth of old forests when LUC area decreases. Our developments provide possibilities to account for continental or global forest demographic change resulting from past anthropogenic and natural disturbances.

Inferring Surface Albedo Prediction Error Linked to Forest Structure at High Latitudes

“…Improving the characterization of forest structure and accounting for gross structural transitions in climate models is crucial to instilling greater confidence in predictions that inform prospective mitigation and adaptation policies involving the forestry sector. The concept of integrating forest “age cohorts” into land models is important for being able to account for time‐dependent structural dynamics in secondary forests (Fisher et al, ; McGrath et al, ; Yue et al, ). The use of NFI data to constrain structural parameters of forest age cohorts can help ensure that the simulated structural transitions match those seen in practice.…”

“…The use of NFI data to constrain structural parameters of forest age cohorts can help ensure that the simulated structural transitions match those seen in practice. Integrating modified forest classifications into existing maps of present‐day land cover (Majasalmi et al, ) can provide a spatially informed basis for constraining structural parameters of “cohort functional types” (Yue et al, ). However, integrating additional development classes or “cohort functional types” into models run at the global scale may impose additional computational challenges.…”

“…Journal of Geophysical Research: Atmospheres et al, 2018) can provide a spatially informed basis for constraining structural parameters of "cohort functional types" (Yue et al, 2018). However, integrating additional development classes or "cohort functional types" into models run at the global scale may impose additional computational challenges.…”

Accounting for forest age in the tile-based dynamic global vegetation model JSBACH4 (4.20p7; git feature/forests) – a land surface model for the ICON-ESM

“…about 15% of global ice-free land, are under some kind of management , with 65% being under regular harvest schemes and another 7% being intensive plantations (Erb et al,20 2017). Often, management practices make use of rotation cycles, as common in shifting-cultivation (Boserup, 1966) or evenaged forest management strategies that historically were common in temperate forests and are still the dominant management ferent versions of ORCHIDEE (Naudts et al, 2015;Yue et al, 2018b) and others. In our study we focus on the second class of DGVMs, as they are more commonly used as LSMs in ESMs.…”

Simulating damage for wind storms in the land surface model ORCHIDEE-CAN (revision 4262)

“…Although Earth system modelling groups dedicate considerable resources to studying the effects of fires (Lasslop et al, 2014), forest management , land cover changes (Swann et al, 2012;Devaraju et al, 2015), and shifting cultivation (Wilkenskjeld et al, 2014;Yue et al, 2018), storm-induced disturbances and their climate feedback are not yet explicitly dealt with in ESMs. The objective of this study is to develop the model capability for the ESM IPSL-CM through its land component ORCHIDEE-CAN to simulate the effects of wind storms on the land surface by building on a good understanding of ecosystem-level processes (Hale et al, 2012(Hale et al, , 2015.…”