Summary of the Article on FATES:

## FATES: The Functionally Assembled Terrestrial Ecosystem Simulator

FATES is an external module that can run within a "Host Land Model" (HLM) like the Community Land Model (CLM). It was derived from the CLM Ecosystem Demography model (CLM(ED)), which was documented in a 2015 study.

The Ecosystem Demography ('ED') concept within FATES is based on the work of Moorcroft et al. (2001). It is a cohort model that represents vegetation competition and co-existence, accounting for the division of the land surface into successional stages and the competition for light between height-structured cohorts of different plant functional types.

The implementation of the Ecosystem Demography concept in FATES links the surface flux and canopy physiology concepts in CLM with numerous additional developments, including:

1. A version of the SPITFIRE (Spread and InTensity of Fire) model from Thonicke et al. (2010).
2. The concept of Perfect Plasticity Approximation from Purves et al. (2008), Lichstein et al. (2011), and Weng et al. (2014), which accounts for the spatial arrangement of crowns.
3. Novel algorithms for the fragmentation of coarse woody debris, physiological optimization of canopy thickness, seed bank accumulation, multi-layer multi-PFT radiation transfer, drought-deciduous and cold-deciduous phenology, carbon storage allocation, and tree mortality under carbon stress.

Overall, FATES is a comprehensive ecosystem simulator that builds upon the CLM(ED) model to provide a more detailed and sophisticated representation of terrestrial ecosystems.