Relationships between climate, radial growth and wood properties of mature loblolly pine in Hawaii and a northern and southern site in the southeastern United States
Production rates of loblolly pine (Pinus taeda L.) in favorable exotic environments indicate that full biological expression of growth potential in loblolly pine has not yet been attained in its native range. In previous work, high productivity in a loblolly pine plantation in Hawaii (HI) was hypothesized to be related to a more favorable climate conducive to year round carbon gain. To better understand the role of climate in limiting loblolly pine growth, relationships between radial growth and climate were examined in mature loblolly pine grown on two sites representing the opposite latitudinal ends of its ecological niche, Mississippi (MS) and North Carolina (NC), and on a third site in Hawaii (HI) representing a more favorable exotic environment. Raw ring widths were detrended and chronologies built for each site. At the northernmost site, ring width index (RWI) was positively correlated to February, April and July temperatures, annual mean temperature of the current and previous year, and annual maximum temperature. In MS trees, the only significant correlation between growth and climate was a positive correlation between RWI and November temperature. Growth at the MS site was likely more impacted by frequent hurricanes. In HI trees, no significant correlations between growth and temperature were observed but RWI was significantly related to precipitation during the dry season, which occurred from May–September. Potential anatomical alterations in the earlywood and latewood transition zones and timing of earlywood and latewood formation were indicated and may account for low ring specific gravity and percent latewood in HI trees. The moderate temperatures at the HI site likely supported high productivity but sensitivity to precipitation in HI trees indicates that reductions in water availability may effect loblolly pine growth even under more moderate temperatures when evaporative demand is low.