A moisture strain index for loblolly pine

Seedlings of Pinustaeda L. were planted in 1982 on a clear-cut site in the northeastern Piedmont of North Carolina. Two intensities of site preparation (chopping and shear–pile–disk) were applied in the previous year, and seedlings were maintained under three intensities of cultural practice (no treatment, application of herbicides, and hand weeding) for control of successional vegetation regrowth. Both site preparation and cultural practice significantly affected pine performance (relative growth rate) and predawn leaf water potentials. Soil water potentials showed no significant treatment effects, even during a severe drought in the summer of 1983. An index of moisture strain for the pine seedlings was developed by regressing predawn leaf water potentials of individual pines against the mean leaf water potentials of all pines using data collected on 5 days in the summer of 1983. This index accounted for 55% of the variation in pine performance. The predictive value of the index resulted from its integra...