Files and scripts to support manuscript Shuman et al 2023 FATES-SPITFIRE ecosystem assembly across tropics

Author(s): Shuman J

Site ID: XX-PTr

Site Name: Pantropical site

Variables: Model output

Date Range: Jan. 1, 1994 - Dec. 31, 2013

Description: The dataset includes the parameter and domain files, relevant output files, and scripts to generate simulations and perform analysis with Jupyter notebooks that support the manuscript Shuman, JK et al 2023 “Dynamic ecosystem assembly and escaping the “fire-trap” in the tropics: Insights from FATES_15.0.0”. We have adapted the fire-behavior and effects module, SPITFIRE, for use with the Functionally Assembled Terrestrial Ecosystem Simulator (FATES), a size-structured vegetation demographic model. We test how climate, fire regime and fire-tolerance plant traits interact to determine the biogeography of tropical forests and grasslands. We assign different fire-tolerance strategies based on crown, leaf and bark characteristics, which are key observed fire-tolerance traits across woody plants. For these simulations, three types of vegetation compete for resources: a fire-vulnerable tree with thin bark, a vulnerable deep crown and fire-intolerant foliage; a fire-tolerant tree with thick bark, a thin crown and fire-tolerant foliage; and a fire-promoting C4 grass. We explore the model sensitivity to a critical parameter governing fuel moisture, and show that drier fuels promote increased burning, an expansion of area for grass and fire-tolerant trees and a reduction of area for fire-vulnerable trees. This conversion to lower biomass or grass areas with increased fuel drying results in increased fire burned area and its effects, which could fee back to local climate variables. Simulated size-based fire mortality for trees less than 20 cm in diameter and those with fire-vulnerable traits is higher than that for larger and/or fire-tolerant trees, in agreement with observations. Fire-disturbed forests demonstrate reasonable productivity and capture observed patterns of aboveground biomass in areas dominated by natural vegetation for the recent historical period, but have a large bias in less disturbed areas. Though the model predicts a greater extent of burned fraction than observed in areas with grass dominance, the resulting biogeography of fire-tolerant, thick-bark trees and fire-vulnerable, thin-bark trees corresponds to observations across the tropics. In areas with more than 2500 mm of precipitation, simulated fire frequency and burned area are low, with fire intensities below 150 kW m-1, consistent with observed understory fire behavior across the Amazon. Areas drier than this demonstrate fire intensities consistent with those measured in savannas and grasslands, with high values up to 4000 kW m-1. The results support a positive grass-fire feedback across the region, and suggest that forests which have existed without frequent burning may be vulnerable at higher fire intensities, which is of greater concern under intensifying climate and land use pressures. The ability of FATES to capture the connection between fire disturbance and plant fire-tolerance strategies in determining biogeography provides a useful tool for assessing the vulnerability and resilience of these critical carbon storage areas under changing conditions across the tropics.

QA/QC: None

Methods Description: A total of five CLM-FATES simulations were completed with four at the 0.5° x 0.5° grid resolution for South America exploring a range of fuel drying ratio parameterizations and one pantropical simulation at the 0.9° x 1.25° grid resolution applying the intermediate fuel drying parameterization. Simulations used three generalized plant vegetation types (PFTs) to represent a fire-intolerant tree, a fire-tolerant tree, and a C4 grass. To explore model sensitivity to fuel drying connectivity to cliamte we modified the parameter for fuel drying using a low, intermediate and high fuel drying parameterization to investigate whether fuel drying acts as a factor in emergent vegetation biogeography across the tropics. Simulations results are analyzed in Python Jupyter notebooks and compared to observations.

Access Level: Public

Originating Institution(s): National Center for Atmospheric Research

Sponsor Organization(s): None

Contact: Shuman, Jacquelyn - National Center for Atmospheric Research (jkshuman@ucar.edu)

Version: 1.0

Dataset Citation: Shuman J (2023): Files and scripts to support manuscript Shuman et al 2023 FATES-SPITFIRE ecosystem assembly across tropics. 1.0. NGEE Tropics Data Collection. (dataset). https://doi.org/10.15486/ngt/1992487

Acknowledgement: Funding for NGEE-Tropics data resources was provided by the U.S. Department of Energy Office of Science, Office of Biological and Environmental Research. We would like to acknowledge high-performance computing support from Cheyenne (doi:10.5065/D6RX99HX) provided by NCAR's Computational and Information Systems Laboratory, sponsored by the National Science Foundation.

Data Link: Download Dataset

Shuman, J. K., Fisher, R. A., Koven, C. D., Knox, R. G., Kueppers, L. M., and Xu, C.: Dynamic ecosystem assembly and escaping the “fire-trap” in the tropics: Insights from FATES_15.0.0, Geosci. Model Dev. Discuss. [preprint], https://doi.org/10.5194/gmd-2023-191, in review, 2023.