Radial changes in wood specific gravity of tropical trees: inter- and intra-specific variation during secondary succession

Variation in wood specific gravity (WSG) within and across species of tropical trees is poorly studied in relation to vegetation change during tropical forest succession. We investigated WSG of 91 species in eight long-term plots along a successional chronosequence in northeastern Costa Rica. Radial changes in WSG were described by the rate of change (slope) along the stem radius. Significant radial changes were found in 42 of 74 species, with 37 species exhibiting increases from inner to outer wood, and 5 exhibiting decreases. Radial increases were commonly observed in species with inner WSG below 0.5, whereas radial decreases were observed in species with inner WSG above 0.7. Wood specific gravity weighted by cross-sectional area (wWSG) varied four-fold among species. Species classified as second-growth specialists had lower wWSG, lower inner and outer WSG, and higher slopes than old-growth specialists; successional generalists showed intermediate trait values. Among 18 species sample...