Thinning and mulching reduce winter drought impacts on dryland forest soil moisture

Abstract

Abstract Regional drought events are becoming more frequent and severe across the western US. In particular, winter droughts have important ecohydrological impacts that last across the entire year. Using a uniquely extensive sensor network across Arizona, we examined soil matric potential during and after 2024–2025 winter drought in thinned, thinned and mulched, and adjacent non-thinned forest sites from three study areas across an elevation and climate gradient. Our results consistently indicate that the winter drought prolonged soil drought at all sites throughout the subsequent spring, when soil matric potential remained below critical thresholds and plants sustained biologically important water stress for up to 293 days. Importantly, thinning treatments reduced these impacts and had significant interaction effects with winter drought. Our results also demonstrate the added benefits of mulching that further enhanced thinning effects on soil matric potential during winter drought periods. Treatment benefits for soil matric potential become particularly significant during winter droughts, although they might not be apparent during periods of average precipitation. Taken together, our results demonstrate that dryland forest thinning and mulching treatments improve winter drought resiliency.