Peatlands transformation in Indonesia has caused immense ecological and environmental degradation. Land use conversion has changed this natural carbon sink to a drought- and fire-prone ecosystem. Public awareness to tackle the drought and fire risk in peatlands has led to the development of drought-fire index. Current knowledge states that both climate and hydrology have a strong influence on drought-induced fire in tropical peatlands, yet the role of soil hydraulic properties in controlling the drying of peats remains unclear. This study develops an improved drought-fire index for tropical peatlands, called the Peat Fire Vulnerability Index, by incorporating groundwater and soil water retention information. We tested the new index on two peatland regions in Kubu Raya and Batanghari, Indonesia, to assess fire danger. We monitored daily rainfall, groundwater tables, and soil moisture from 2018 to 2019 on eight stations in the peatlands. Our model was calibrated against the observed drought index of two stations, and the results were verified with actual fire events through daily fire hotspots and fire burned areas in the other six stations. Results showed that soil-hydrological properties influenced the moistening and drying of peats through capillarity. Our model showed good performance in assessing fire danger during the calibration period, as indicated by three employed statistical metrics: the RMSE-standard deviation ratio (RSR = 0.57), Kling-Gupta Efficiency (KGE = 0.81), and percent bias (PBIAS = 1%). For verification, all observed fire events fell in high and extreme fire danger classes predicted by PFVI. Further, our findings revealed the importance of the groundwater table as a threshold of fire events. The high fire danger class was mostly found when groundwater table dropped below 40 cm, and burned areas only occurred when the groundwater table was below 60 cm. These findings suggest that our drought-fire index can be used as a peat fire risk management tool, and its application may minimize fire risks in tropical peatlands.

印度尼西亚的泥炭地改造造成了巨大的生态和环境退化。土地利用转换已将这种天然碳汇转变为易受干旱和火灾影响的生态系统。公众对解决泥炭地干旱和火灾风险的认识导致了干旱火灾指数的发展。目前的知识表明，气候和水文对热带泥炭地干旱引起的火灾有很大影响，但土壤水力特性在控制泥炭干燥方面的作用仍不清楚。本研究通过结合地下水和土壤保水信息，开发了一种改进的热带泥炭地干旱火灾指数，称为泥炭火灾脆弱性指数。我们在印度尼西亚 Kubu Raya 和 Batanghari 的两个泥炭地地区测试了新指数，以评估火灾危险。我们监测了每日降雨量，2018 年至 2019 年泥炭地八个站点的地下水位和土壤湿度。我们的模型根据两个站点的观测干旱指数进行了校准，结果通过其他六个站点的日常火灾热点和火灾燃烧区域的实际火灾事件进行了验证。结果表明，土壤水文特性通过毛细作用影响泥炭的润湿和干燥。我们的模型在校准期间在评估火灾危险方面表现出良好的性能，如三个采用的统计指标所示：RMSE 标准偏差比 (RSR = 0.57)、Kling-Gupta 效率 (KGE = 0.81) 和百分比偏差 (PBIAS = 1%）。为了验证，所有观察到的火灾事件都属于 PFVI 预测的高度和极端火灾危险等级。更远，我们的研究结果揭示了地下水位作为火灾事件阈值的重要性。高火灾危险等级多发生在地下水位低于40 cm 时，仅在地下水位低于60 cm 时发生火灾。这些发现表明，我们的干旱火灾指数可以用作泥炭火灾风险管理工具，其应用可以最大限度地减少热带泥炭地的火灾风险。