Evaluation of Compression Wood Incidence Under Different Thinning Regimes in Late Rotation of Pinus taeda

Compression wood (CW) negatively affects the industrial quality of Pinus taeda by causing distortion in sawn boards and is visually characterized by a darker reddish colour. Thinning is considered a key factor influencing its formation, but the reported effects have been inconsistent. This study evaluated CW incidence at final rotation under five thinning regimes: 500-200, 500-325, 800-600-400, 700-450, and 1000-650 trees.ha−1. The defect was assessed on log ends, basal discs, and sawn boards. Although overall CW severity was low, regimes differed significantly. The 500-325 trees.ha−1 regime showed the highest stain and board defects, while the 500-200 trees.ha−1 regime of similar intensity had lower values, indicating that intensity alone does not explain the occurrence of defects. After thinning, CW in growth rings increased and was positively associated with ring width and negatively with stand density index, indicating that reduced competition and accelerated radial growth are linked to higher formation levels. Visible CW staining on log ends was moderately correlated with board defects, indicating its potential as a practical, low-cost indicator of log quality. Thinning affects compression wood through its impact on growth and stand structure. In addition to intensity, timing and the effect of the wind must also be considered. Moderately intensive regimes help minimize defects, although their practical adoption may be limited by commercial priorities.