Understanding the spatiotemporal variability of soil moisture is essential for advancing hydrological, ecological, and agricultural management practices. This study investigates soil moisture dynamics across three distinct hydroclimatic periods (wet, dry, and wet-dry transitions) in a headwater catchment in central Pennsylvania, USA, characterized by heterogeneous soils and variable topography. We aim to elucidate key influencing factors and optimize catchment-scale monitoring strategies. Using the Index of Temporal Stability (ITS), we assessed the temporal stability of soil moisture and identified representative locations. Redundancy Analysis (RDA) was applied to explore the impacts of influencing factors on soil moisture variability. Results revealed that dominant controls varied substantially across periods and soil horizons. The temporal stability of soil moisture was the highest during wet periods, primarily governed by topographic attributes, but decreased during dry and transitional periods. During dry periods, soil moisture dynamics were influenced by a combination of soil composition and slope characteristics, while transitional periods exhibited strong sensitivity to Preferential Flow Frequency (PFF) and slope attributes. Among time-variant factors, air temperature and evapotranspiration emerged as critical regulators of soil moisture dynamics. A single representative location, characterized by Topographic Wetness Index (TWI) values close to the catchment's mean and relatively low PFF, provided robust estimates of areal mean soil moisture across the study period (R-2 > 0.86). However, additional monitoring locations were needed to maintain accuracy during dry and transitional periods. These findings improve the understanding of soil moisture variability in forested catchments and offer insights for designing cost-effective monitoring networks to support hydrological modeling and management.