POPULATION-STRUCTURE AND SPATIAL PATTERN OF 2 COASTAL POPULATIONS OF OCALA SAND PINE (PINUS-CLAUSA (CHAPM EX ENGELM) VASEY EX SARG VAR CLAUSA WARD,D.B.)

Two coastal populations of Ocala sand pine (Pinus clausa (Chapm. ex En gelm.) Vasey ex Sarg. var. clausa D. B. Ward) in southeastern Florida were compared for effects of disturbances occurring at different scale s on spatial dispersion and age structure. Fire has been excluded from the older population (JDO) since at least 1947; the younger populatio n (JDY) experienced a wildfire in 1971. The two populations differed m arkedly in size and age structure and spatial dispersion. Density was greater and basal area was lower in JDY than in JDO. Ages in JDY were bimodally distributed, with a primary peak from 11-20 years old (delay ed recruitment after the 1971 fire) and a secondary peak from 41-45 ye ars old (earlier post-fire recruits that survived the 1971 fire). Stem s in JDY were aggregated, with a positive association between seedling s and small trees. JDO had experienced more wind damage, heart rot, an d mortality than JDY. Ages were unimodally distributed in JDO, with th e peak from 61-70 years old; and stem distribution was random to regul ar. Although others have reported regeneration in canopy gaps in senes cent Ocala sand pine populations in the absence of fire, JDO has shown no recruitment since 1950. With continued fire suppression and mortal ity of sand pine in JDO, xeric hardwoods in the understory will likely become increasingly dominant.