VOMcases v0.2

Does maximization of net carbon profit enable the prediction of vegetation behaviour in savanna sites along a precipitation gradient? Ecological and hydrological processes are strongly interlinked by vegetation and its properties. Models often use static values for vegetation properties, that are in reality highly dynamic, or prescribe vegetation properties based on remotely sensed data. The Vegetation Optimality Model (VOM, Schymanski et al., 2009) optimizes vegetation properties in order the optimize the Net Carbon Profit, i.e. the difference between the total carbon taken up by photosynthesis and all the carbon costs of the plants. The VOM schematizes perennial trees and seasonal grasses each as a single big leaf with an associated root system, and optimizes rooting depths, foliage cover, photosynthetic capacity and water use strategies. In this repository, the Vegetation Optimality Model is applied along the North-Australian Tropical Transect (NATT). The NATT consists of five study sites with an increasing rainfall amount from North to South. Long-term data on evaporation and CO2-measurements are available at these sites, which are used to validate the modelling results. In this study, we hypothesize that: 1. The optimality-based model is not substantially worse at capturing the seasonal amplitudes and mean annual values of observed carbon and water fluxes than conventional models analyzed by Whitley et al. (2016) along the NATT. 2. The plant hydraulic system has carbon costs that only depend on the plant size, represented by root depth and vegetation cover, and a constant independent of species and climate (i.e. the water transport cost parameter). 3. The optimality-based dynamic vegetation cover, as a result of maximizing NCP, reproduces the carbon and water fluxes better than a prescribed mean seasonal phenology in the VOM, derived from remote sensing data. 4. The optimality-based constant rooting depth at each site, as a result of maximizing NCP, reproduces the carbon and water fluxes better than a prescribed homogenous rooting depth across all sites in the VOM. How to use this project This project contains all pre- and post-processing scripts for the model runs of the VOM along the NATT. All final figures are in the notebooks, as well as the supplementary analysis. These scripts can be re-used for other VOM-applications. See also the README.md for more details about the contents of this repository. Related publications This repository is related to the following manuscripts: Nijzink, R. C., Beringer, J., Hutley, L. B., and Schymanski, S. J.: Step-wise modifications of the Vegetation Optimality Model, Geosci. Model Dev. Discuss. [preprint], https://doi.org/10.5194/gmd-2021-151, in review, 2021 Nijzink, R. C., Beringer, J., Hutley, L. B., and Schymanski, S. J.: Does maximization of net carbon profit enable the prediction of vegetation behaviour in savanna sites along a precipitation gradient?, Hydrol. Earth Syst. Sci. Discuss. [preprint], https://doi.org/10.5194/hess-2021-265, in review, 2021Funded by the Luxembourg National Research Fund, ATTRACT programme (A16/SR/11254288