Table 1_Long-term tree mortality prediction following stem breakage in loblolly pine (Pinus taeda L.) plantations: implications for management in the southeastern United States.docx

IntroductionLoblolly pine (Pinus taeda L.) plantations in the southeastern United States are increasingly vulnerable to climate-driven disturbances that cause stem breakage and elevate tree mortality. Consequently, it is imperative to develop adaptive management strategies following stem breakage for forest managers and landowners to mitigate tree mortality and sustain forest productivity. However, predictive frameworks for post-breakage mortality remain underdeveloped, hampering adaptive management efforts.
MethodsWe conducted a split-plot experiment in four mid-rotation plantations, applying two whole-plot silvicultural treatments (no thinning vs. thinning) and five subplot treatments defined by the proportion of trees damaged (PTD: 0, 25, 50, 75, 100%). Stem breakage was simulated by rifle shooting of main stems, and individual trees were monitored for 12 years. We developed a multiple logistic regression model including thinning, plot-level damage (PTD), tree-level damage severity (PSD), diameter at breast height (DBH), total height (HT), and crown height (CRNHT), and used parametric bootstrapping (10,000 iterations) to quantify uncertainty.
ResultsOur findings highlight three key patterns: (1) Short-term mortality (<4 years) remained low but increased sharply over the long term following stem breakage; (2) Larger DBH and greater tree height reduced mortality risk; and (3) Plot-level damage proportion had a stronger influence on mortality than individual-tree damage severity.
DiscussionThese results highlight the dominant role of plot-level damage regimes and tree size in long-term survival after stem breakage. Incorporating these insights into adaptive thinning and disturbance management frameworks will help sustain productivity and resilience in loblolly pine plantations under escalating climate extremes.