STAND AND TREE CHARACTERISTICS AND STOCKABILITY IN PINUS-TAEDA PLANTATIONS IN HAWAII AND SOUTH-CAROLINA

Stand structure and crown architecture of loblolly pine (Pinus taeda L .) spacing trials in Hawaii and South Carolina were examined for attri butes that would explain markedly different stockabilities (stand dens ity per mean stand DBH), respectively, 1740 and 850 trees/ha at a quad ratic mean stand DBH of 25 cm. In plots spaced at 2.4 X 2.4 m, these s tockabilities produced 604 m3/ha at age 25 in Hawaii, and 297 m3/ha in South Carolina. Data collected in these stands indicate that stockabi lity differences were associated with differences in tree size-class s tructure, crown length, and leaf area. Both stands were characterized by a two-tiered height structure, but the crown bases of trees in the subdominant class in Hawaii extended 1-2 m below the bases of the crow ns of the dominant height class. In the South Carolina stands the crow n bases of both height classes were at the same level. Green crown len gths in Hawaii were 4-7 m longer than in South Carolina, and the assoc iated crown leaf area of 63.9 m2 was five times greater. The differenc es in stockability was attributed to the Hawaiian site and climate, wh ich provide a long growing season, high solar radiation, high sun angl e, favorable temperatures, and a favorable soil moisture regime and fo liage nutrient status, and to a lack of significant insect and disease pests. The influence of genotype on stockability was not testable wit h these data.