Forest Demography and Ecohydrological Dynamics Incorporating in the T&C (Tethys-Chloris) model

Forest ecosystems play a crucial role in regulating large-scale hydrological and biological cycles on the land surface. They currently store approximately 45% of the total carbon on land, sequester around 80 Pg of carbon annually, responsible to 70–80% of total terrestrial evapotranspiration. Modeling the coupled carbon and water dynamics of forests remains a significant challenge due to their structural complexity. Approximately 25% of forests are rejuvenating, short-stature forests recovering from recent disturbances, while older forests are typically highly diverse, with multiple species competing for resources. To effectively model these dynamics, advancements in representing structural complexity are essential. These models need to adopt parsimonious approaches that account for the limited availability of data while maintaining accuracy and scalability.

Among the various simulation approaches, we have selected the Tethys-Chloris (T&C) model in this study. The T&C model offers several advantages, such as highly customizable parameters for representing multiple species and detailed soil carbon pools to simulate soil carbon dynamics and soil biogeochemistry. These features make the T&C model a promising tool for accurately simulating and predicting forest ecosystem behaviour. However, its forest demography component is currently simplified, assuming uniform tree heights and properties within the same plant functional type (PFT). While this assumption works well for fully mature forests, it is inadequate for forests undergoing large-scale recruitment, growth, or mortality. These dynamic forests are increasingly common due to anthropogenic activities and climate change.

To address this limitation, we propose changing the original cohort-based forest demography in the T&C model. We plan to develop a new parsimonious forest demography scheme to represent the dynamics of forest ecosystems transportable to other land surface models. This scheme will utilize a tiling approach to represent species in the forest. In this scheme, we will redistribute research forests to a cohort-based allocation of tree species to represent the ecosystem's diversity and dynamics. The perfect plasticity approximation will represent the canopy's movement and closure. The interspecies competition for light, water and nutrients between cohorts of different heights and densities will be used to make simulations closer to reality.

To validate these enhancements to the T&C model, we are utilizing regional forest data from diverse climates, including flux data collected from observatories in North American, European and Amazon forests. Incorporating more diverse and precise datasets will further enhance the accuracy of forest ecosystem simulations and predictions.