Longleaf Pine Drought Resilience is More Sensitive Than Resistance to Competition Reduction but Influenced by Site Conditions

Abstract

Competition reduction is widely considered an effective strategy for mitigating drought impacts. Yet little is known about the efficacy of this strategy on drought-tolerant species, particularly across contrasting silvicultural treatments. We reconstructed annual growth of longleaf pine (Pinus palustris) from increment cores to evaluate whether silvicultural treatments consistently influenced drought response across three regional droughts (2000, 2006–2007, 2011) at three sites. Drought response was quantified using five indices (resistance, resilience, recovery, recovery rate, average growth reduction) Post-treatment density ranged from ~16–18 m² ha⁻¹ in control treatments to ~4.7–5.9 m² ha⁻¹ in shelterwood methods. Treatment effects were absent for resistance and average growth reduction but significant for resilience, recovery, and recovery rate. Plot-level net change in basal area emerged as the most consistent predictor of post-drought performance. The length of the growing season (as indicated by degree-day indices) was an important predictor of resistance, resilience, and recovery. Overall, resistance, resilience, and recovery were emergent, multidimensional outcomes that were not consistently improved by basal area reduction alone.