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

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. This dataset was originally published on the NGEE Tropics Archive and is being mirrored on ESS-DIVE for long-term archival 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.

本数据集包含参数与域文件、相关输出文件，以及用于生成模拟与开展分析的Jupyter笔记本（Jupyter notebooks）脚本，配套支持Shuman等人2023年发表的论文《动态生态系统组装与逃离热带“火陷阱”：来自FATES_15.0.0的见解》。我们对火灾行为与影响模块（SPITFIRE）进行了适配，使其可与功能组装陆地生态系统模拟器（Functionally Assembled Terrestrial Ecosystem Simulator, FATES）联用——后者是一种基于个体大小结构的植被人口统计模型。我们探究了气候、火灾制度与植物耐火性状如何相互作用，共同决定热带森林与草原的生物地理学分布。我们基于冠层、叶片与树皮特征划分了不同的耐火策略，这些特征是木本植物中已被观测到的关键耐火性状。在本模拟实验中，三类植被将竞争资源：一是树皮较薄、冠层较深且叶片耐火性较差的易受火灾危害的乔木；二是树皮较厚、冠层较薄且叶片耐火性较强的耐火乔木；三是会促进火灾发生的C4草本植物。我们探究了模型对调控燃料湿度的关键参数的敏感性，结果显示更干燥的燃料会加剧燃烧，扩大草本与耐火乔木的分布范围，同时缩减易受火灾危害的乔木的分布面积。这种向低生物量区域或草本主导区域的转化，伴随燃料干燥程度提升，会导致过火面积及其影响增加，进而可反馈至局地气候变量。针对直径小于20cm的乔木以及具备易受火灾危害性状的乔木，模拟得到的基于个体大小的火灾死亡率，高于更大尺寸或/且具备耐火性状的乔木，这与观测结果一致。受火灾干扰的森林展现出合理的生产力，且在近期历史时期的天然植被主导区域中，能够匹配观测到的地上生物量分布模式，但在受干扰较少的区域存在较大偏差。尽管模型预测的过火比例高于草本主导区域的观测值，但最终得到的耐火厚皮乔木与易受火灾危害的薄皮乔木的生物地理学分布，与整个热带地区的观测结果相符。在年降水量超过2500mm的区域，模拟得到的火灾频率与过火面积均较低，火灾强度低于150 kW·m⁻¹，这与整个亚马逊地区观测到的林下火灾行为一致。降水低于该阈值的区域，火灾强度与稀树草原及草原中测得的数值相符，最高可达4000 kW·m⁻¹。研究结果支持整个区域存在正向的草-火反馈机制，同时表明长期未经历频繁火灾的森林在更高火灾强度下可能会变得脆弱，在气候与土地利用压力加剧的背景下，这一问题更令人担忧。FATES能够捕捉火灾干扰与植物耐火策略在决定生物地理学分布中的关联，这为评估热带地区不断变化的环境下这些关键碳存储区域的脆弱性与恢复力提供了实用工具。本数据集最初发布于NGEE热带地区档案馆（NGEE Tropics Archive），目前已镜像至ESS-DIVE以实现长期归档。致谢：NGEE-Tropics数据资源的资助由美国能源部科学办公室生物与环境研究局提供。我们感谢由美国国家科学基金会资助的NCAR计算与信息系统实验室提供的Cheyenne高性能计算支持（doi:10.5065/D6RX99HX）。