Longleaf Pine Pyrogenicity and Turkey Oak Mortality in Florida Xeric Sandhills

Logistic multiple regression models were constructed for turkey oak crown survival and resprouting in two experimental fires. Crown survival patterns were similar in the mild and the more intense fire. Crown survival was positively related to "turkey oak diameter at breast height (dbh)," and "distance to the nearest large longleaf pine"; it was inversely related to the "dbh of the nearest pine." The crowns of small turkey oaks (2.5—5.5 cm dbh) rarely survived the intense fires fueled by needle litter in the vicinity of longleaf pines, while large turkey ocaks (>10 cm dbh) had high crown survival regardless of location. In the mild fire, pines affected the survival of small turkey oaks within a distance of at least 10 m, while in the hotter fire pines appeared to affect the survival of small turkey oaks within at least 25 m. In the mild fire, 68% of the crown—killed oaks resprouted, and the probability of resprouting was inversely related to both "turkey oak dbh," and "distance to the nearest pine." Most trees that failed to resprout had delayed crown mortality. In the hotter fire, 95% of crown—killed oaks resprouted, and resprouting was inversely related to "turkey oak dbh." Although the pyrogenicity of longleaf pine also leads to segregation of adult pines and their seedlings, most oaks are adversely affected by fires within the zone of maximum pine seedling recruitment. Thus, reduced competition from oaks may increase the fitness of longleaf pines and favor selection for pyrogenicity.