Post-Rainfall Dynamics and Hourly Prediction of Surface Fine Dead Fuel Moisture Across Contrasting Land-Cover Conditions in Northeast China

This study developed and validated hour-scale models for predicting surface fine dead fuel moisture content (FMC) during the first 24 h after rainfall across four land-cover types in the Qipanshan region, Northeast China. It further examined differences in moisture retention among fuelbeds, the ability of weighted least squares (WLS) to address heteroscedasticity relative to ordinary least squares (OLS), and the influence of canopy closure on the dominant controls of post-rainfall drying. Simulated rainfall of 9, 20, 40, and 70 mm was applied to 219 quadrats in Betula platyphylla Sukaczev, Larix gmelinii (Rupr.) Kuzen., and Pinus sylvestris var. Mongolica Litv. stands and on cutover land during autumn 2022 and spring 2024. FMC was monitored for 24 h together with 10-min microclimatic observations. Box–Cox transformation, all-subsets regression, OLS/WLS comparison, Breusch–Pagan tests, AIC, and relative-importance analysis were used. Drying exhibited a two-phase pattern, with rapid early moisture loss followed by marked attenuation, while moisture gain changed little above 40 mm rainfall. B. platyphylla had the highest peak and residual FMC, whereas cutover land had the lowest. WLS stabilized residual variance in all 12 models (Breusch–Pagan p = 0.40–0.99) and yielded lower AIC values than OLS. The models explained 50.3–95.8% of FMC variance. Beneath closed canopies, drying duration, initial FMC, and rainfall depth were the principal controls, whereas air temperature and wind speed were more influential on cutover land. These findings provide a quantitative basis for hour-scale assessment of post-rainfall fuel dryness and potential ignitability.