STRUCTURAL CHARACTERISTICS OF OLD-GROWTH AND 2ND-GROWTH STANDS OF LONGLEAF PINE (PINUS-PALUSTRIS) IN THE GULF COASTAL REGION OF THE USA

Comparisons of old- and second-growth stands of longleaf pine (Pinus p alustris) may be useful for setting long-term objectives for the resto ration and management of second-growth stands. We quantified structura l differences among (1) one xeric old-growth stand, (2) two xeric seco nd-growth stands, and (3) one seasonally flooded flatwoods second-grow th stand using quadrats ranging from 100 m(2) to 10,000 m(2). We estim ated the mean density and size of pines, the frequency and size of ope n spaces, and the scale of aggregation for each stand. The mean densit y of pines was higher in the two xeric second-growth stands than in th e old-growth stand, but variability at the old-growth stand was higher , suggesting discrete patches of densely stocked small trees, interspe rsed with larger trees and open spaces. This pattern was not present a t either xeric second-growth stand. In contrast, the density of trees at the flatwoods site was lower and the frequency of open areas higher than for any other stand. The size class distribution at the old-grow th stand was characterized by more small and large trees and fewer int ermediate-sized trees than at the second-growth stands. The mean size of all trees at the old-growth stand was larger than at the second-gro wth stands, but it decreased with increasing quadrat size, reflecting the inclusion of smaller trees in larger quadrats; this pattern was no t present in two of the three second-growth stands. The dynamics of ol d-growth stands can provide a framework for interpreting patterns obse rved in second-growth stands. In an old-growth stand, the death of old er, larger trees creates open patches allowing recruitment of juvenile s. Patches of suitable sie for recruitment were not present at the xer ic second-growth stands. Proactive management of xeric second-growth s tands by selective removal of small groups of overstory trees would al low a more uneven size distribution and would create open areas for re cruitment. The flatwoods site differed from the xeric second-growth si tes and thus is likely to require different management regimes.