Growth and physiology of loblolly pine in response to long-term resource management: defining growth potential in the southern United States
Leaf physiology and stem growth were assessed in loblolly pine (Pinus taeda L.) in response to 10 to 11 years of treatment with weed control (W), weed control plus irrigation (WI), weed control plus irrigation and fertigation (WIF), or weed control plus irrigation, fertigation, and pest control (WIFP) to determine whether increased resource availability can push productivity of loblolly pine closer to its biological growth potential expressed in favorable, exotic environments. Maximum basal area and stem biomass were 41 m2ha-1 and 172 Mg ha-1, respectively, in response to fertigation. Stem-wood biomass production was positively and linearly related to basal area. Belowground woody biomass was highest in the WIF and WIFP treatments averaged 50 Mg ha-1, but the W and WI treatments exploited a greater area of soil with low-density coarse roots. Fertigation increased foliar nitrogen concentration with foliage biomass, but treatment had no effect on leaf physiological parameters or growth efficiency. Comparison with growth rates reported for loblolly pine in Hawaii revealed that loblolly pine grown in its native range can produce high yields observed in exotic environments when stands are below maximum carrying capacity.