Can thinning and mulching help dryland forests withstand winter drought?

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Regional droughts are becoming more frequent and severe across the western US, and winter droughts can have important ecohydrological impacts throughout the year.

Researchers used a uniquely extensive sensor network across Arizona to examine soil matric potential during and after the 2024–2025 winter drought. They compared thinned sites, thinned and mulched sites, and adjacent non-thinned forest sites in three study areas spanning an elevation and climate gradient.

Winter drought prolonged soil drought at all sites throughout the following spring. Soil matric potential remained below critical thresholds, and plants experienced biologically important water stress for up to 293 days.

Thinning reduced these impacts and had significant interaction effects with winter drought. Mulching provided additional benefits, further enhancing the effects of thinning on soil matric potential during winter drought periods. Treatment benefits for soil matric potential were particularly significant during winter droughts, though they might not be apparent during periods of average precipitation. Together, the results indicate that thinning and mulching improve dryland forest resilience to winter drought.