Surface Thermal State, Antecedent Hydroclimate, and Post-Fire Vegetation–Water Response in the Zambezi River Basin: A Multi-Source Environmental Time-Series Analysis

Wildfire in African savannas reflects coupled surface thermal, hydroclimatic, vegetation, and disturbance processes, but basin-scale time-series analyses can overstate mechanisms when temporal dependence and spatial heterogeneity are ignored. We assembled a monthly 2003–2024 multi-source environmental dataset for the Zambezi River Basin ($n=263$) and nine Level-4 HydroBASINS units, using quality-controlled MODIS burned area, normalized difference vegetation index (NDVI), daytime land surface temperature (LST), and evapotranspiration (ET), together with CHIRPS precipitation and GLDAS-2.1 Noah 0–10 cm soil moisture. Primary inference used heteroskedasticity- and autocorrelation-consistent regressions, expanding-window Random Forest validation, false-discovery-rate-controlled distributed-lag tests, and sub-basin robustness; vector autoregression was retained as a secondary diagnostic. Current-month burned-area anomalies were positively associated with LST ($\beta =0.340$, $p=0.0015$) and negatively associated with near-surface soil moisture ($\beta =-0.326$, $p=0.0005$). Over 1–9 months, precipitation and soil-moisture histories were jointly supported after multiplicity correction, whereas basin-wide NDVI, ET, and LST histories were not. Burned-area history was followed by cumulative 0–6 month declines in NDVI ($\beta =-0.280$, 95% CI $[-0.452,-0.107]$) and ET ($\beta =-0.214$, 95% CI $[-0.419,-0.008]$). Directions were broadly consistent across sub-basins, although magnitudes varied. The evidence supports time-scale-specific conditional associations without structural-causal claims.