Abstract Soil moisture regulates plant water supply and drought sensitivity in tropical forests, yet its vertical and topographic variation remains poorly characterized. We combined high‐frequency time‐domain reflectometry measurements from 5 to 100 cm across plateau, slope, and valley landforms at the Zona Florestal 2 research site north of Manaus, Central Amazonia, to quantify how soil moisture memory, timing of responses to rainfall, dry‐down rates ( τ ), and soil–water depletion vary across these contrasting landforms. Landform‐specific soil moisture calibration curves ensured accurate volumetric water content estimates in these highly weathered soils. During the 2023 dry‐to‐wet transition (August–November), soil moisture memory showed strong topographic contrasts, with valley profiles increasing from ∼47 h at 5 cm to ∼154 h at 100 cm, while plateaus exhibited higher near‐surface persistence (∼124 h at 5 cm) but weaker memory at depth. Dry‐down behavior reinforced these differences as valley soils exhibited τ values exceeding ∼200 h, more than double the characteristic τ of plateau soils (∼90 h). Rainfall–soil moisture correlations indicated immediate responses at shallow depths in valleys and progressively longer lags with depth on plateaus and slopes. These hydrologic patterns were mirrored in depletion profiles, which declined sharply below 30 cm on plateaus but remained high and sustained throughout the upper meter in slopes and valleys. Together, these findings provide the first depth‐resolved field measurements of soil moisture memory, rainfall coupling, dry‐down constants, and depletion dynamics across major upland landforms in Central Amazonia and offer clear observational benchmarks for improving land‐surface and ecosystem model representations of soil–water processes.
Negrón‐Juárez et al. (Sun,) studied this question.
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