| Scope and Method of Study: I studied the resprouting response from basal crooks of shortleaf pine (Pinus echinata Mill) seedlings top-killed after an early spring prescribed fire in northwestern, AR. The variables measured were pre-fire seedling height, ground line diameter, basal crook diameter, basal crook depth, percent crown scorch, surface fire maximum temperature, and basal crook maximum temperature. These seedlings were monitored over the growing season for survival, sprout count, and sprout size. The scope was to determine the purpose of the basal crook morphology, and define parameters that increase the likelihood of shortleaf pine survival following fire management activities. In the second study I compared growth rate, needle morphology, basal crooking, resproutting capacity, first-year establishment and survival, and gas exchange and physiological measurements (Anet, Ci, g s, delta13C, Psi) of young seedlings of shortleaf pine, loblolly pine (Pinus taeda L.), and their F1 hybrid. The study was performed in a raised bed nursery over the course of three growing seasons. The scope was to determine which characteristics parent species pass on to their hybrid offspring that have helped the hybrids increase in frequency over the past 60 years.;Findings and Conclusions: In the first experiment, 40% of seedlings did not resprout and died following fire. Over the course of the growing season 40% of the resprouted seedlings died. Resprouted seedlings that survived the growing season had similar size and soil depth to crook as seedlings that initially died, which were smaller and shallower than those that resprouted and died. Crook temperature and crown scorch values were similar for those that resprouted and survived the growing season compared to those that initially died, suggesting that the ability of top-killed seedlings to resprout following fire is more sensitive to fire and heat damage, while the ability of a resprouted seedling to survive is more sensitive to seedling size. In the second study, hybrids were intermediate for most needle morphology traits, resprouting capacity, and water use efficiency, but were similar to loblolly pine in growth rate, early establishment and survival (both higher than shortleaf pine), and strong basal crooking (lower than shortleaf pine). These traits likely helped hybrids out-compete parent species in the absence of fire which favors shortleaf pine establishment. |
