A new version of the CABLE land surface model (Subversion revision r4601) incorporating land use and land cover change, woody vegetation demography, and a novel optimisation-based approach to plant coordination of photosynthesis

Abstract

The Community Atmosphere-Biosphere Land Exchange model (CABLE) is a land surface model (LSM) that can be applied stand-alone and provides the land surface-atmosphere exchange within the Australian Community Climate and Earth System Simulator (ACCESS). We describe new developments that extend the applicability of CABLE for regional and global carbon-climate simulations, accounting for vegetation responses to biophysical and anthropogenic forcings. A land use and land cover change module driven by gross land use transitions and wood harvest area was implemented, tailored to the needs of the Coupled Model Intercomparison Project 6 (CMIP6). Novel aspects include the treatment of secondary woody vegetation, which benefits from a tight coupling between the land use module and the Population Orders Physiology (POP) module for woody demography and disturbance-mediated landscape heterogeneity. Land use transitions and harvest associated with secondary forest tiles modify the annually resolved patch age distribution within secondary vegetated tiles, in turn affecting biomass accumulation and turnover rates and hence the magnitude of the secondary forest sink. Additionally, we implemented a novel approach to constrain modelled GPP consistent with the coordination hypothesis and predicted by evolutionary theory, which suggests that electron-transport-andPublished by Copernicus Publications on behalf of the European Geosciences Union.

Higher than expected CO2 fertilization inferred from leaf to global observations

“…Linear trends : 0.061 ± 0.02 (1 SE) PgC/year 2 (GCP) and 0.067 ± 0.01 PgC/year 2 (CABLE). See also Figure S1 for metrics related to the NLS heterogeneity (Haverd, Smith, et al, 2013), and a module for land use and land management (POPLUC; Haverd et al, 2018). The land use and land cover change module is driven by gross land use transitions and wood harvest area.…”

“…and (c) coordinated leaf nitrogen investment in electron transport and Rubisco-limited steps in the photosynthesis chain, such that they adjust seasonally and across biomes to be co-limiting (Haverd et al, 2018). This version also includes a new diagnostic elasticity = A c s c s A that allows the GPP increase attributable to the leaf-level component of the CO 2 fertilization effect to be isolated as A c s Δc s , where c s is the CO 2 concentration at the leaf surface.…”

“…CABLE represents the coordination of C 3 photosynthesis, adjusting electron transport and Rubisco-limited rates (Farquhar, Caemmerer, & Berry, 1980) to be co-limiting (Haverd et al, 2018). This is achieved by dynamically optimizing the ratio b JV of the maximum rate of electron transport (J max ) to the Rubisco-catalyzed maximum rate of carboxylation (V cmax ) at standard temperature.…”

Multimodel Analysis of Future Land Use and Climate Change Impacts on Ecosystem Functioning

“…CABLE-POP consists of a biophysics core (Haverd et al, 2016;Kowalczyk et al, 2013;Y. CABLE-POP represents coordination of C3 photosynthesis, adjusting electron-transport-and Rubisco-limited rates seasonally to be colimiting (Haverd et al, 2018), leading to a higher simulated CO 2 fertilization effect on photosynthesis than LPJ and LPJ-GUESS (the less CO 2 -sensitive electron-transport limitation dominates in these models). Generic patch-destroying disturbances occur with an average return interval of 100 years.…”

“…CABLE-POP consists of a biophysics core (Haverd et al, 2016;Kowalczyk et al, 2013;Y. P. Wang et al, 2011), the CASA-CNP biogeochemistry module (Y. P. , the POP module for woody demography and disturbance-mediated landscape heterogeneity (Haverd et al, 2013;Haverd et al, 2014), and a module for land use and land management (POPLUC; Haverd et al, 2018). Generic patch-destroying disturbances occur with an average return interval of 100 years.…”