Structural characteristics of old- and second-growth stands of longleaf pine (Pinus palustris) in the gulf coastal region of the U.S.A.

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Comparisons of old- and second-growth stands of longleaf pine (Pinus palustris) may be useful for setting long-term objectives for the restoration and management of second-growth stands. We quantified structural differences among (1) one xeric old-growth stand, (2) two xeric second-growth stands, and (3) one seasonally flooded flatwoods second-growth stand using quadrats ranging from 100 m2 to 10,000 m2. We estimated the mean density and size of pines, the frequency and size of open spaces, and the scale of aggregation for each stand. The mean density of pines was higher in the two xeric second-growth stands than in the old-growth stand, but variability at the old-growth stand was higher, suggesting discrete patches of densely stocked small trees, interspersed with larger trees and open spaces. This pattern was not present at 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-growth stand was characterized by more small and large trees and fewer intermediate-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-growth stands, but it decreased with increasing quadrat size, reflecting the inclusion of smaller trees in larger quadrats; this pattern was not present in two of the three second-growth stands. The dynamics of old-growth stands can provide a framework for interpreting patterns observed in second-growth stands. In an old-growth stand, the death of older, larger trees creates open patches allowing recruitment of juveniles. Patches of suitable size for recruitment were not present at the xeric second-growth stands. Proactive management of xeric second-growth stands by selective removal of small groups of overstory trees would allow a more uneven size distribution and would create open areas for recruitment. The flatwoods site differed from the xeric second-growth sites and thus is likely to require different management regimes.

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Conservation Biology

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