Effects of spring prescribed fire on short-term, leaf-level photosynthesis and water use efficiency in longleaf pineThis article is part of a larger document. View the larger document here.
Fire is a natural and important environmental disturbance influencing the structure, function, and composition of longleaf pine (Pinus palustris Mill.) ecosystems. However, recovery of young pines to leaf scorch may involve changes in leaf physiology, which could influence leaf water-use efficiency (WUE). This work is part of a larger seasonal burning study containing three treatments: spring burn, fall burn, and no burn. The study site is a 21.4-ha (53-acre) longleaf pine plantation planted in 2005 and located on the Winn Ranger District of the Kisatchie National Forest in central Louisiana. This work assessed changes in leaf gas exchange and their resultant WUE in 7-year-old longleaf pine among spring burned and no burn (control) treatments during the 2011 and 2012 growing seasons. Treatment effects on intrinsic WUE [carbon assimilation/ stomatal conductance (gs); iWUE] were assessed using an infrared gas analyzer. We hypothesized that leaf area loss resulting from scorch will: (1) increase photosynthesis, and (2) increase leaf-level iWUE as a result of increased photosynthesis. In the 3 months after the prescribed burn, we observed increases in photosynthesis (ASat) in the new foliage of scorched trees that decreased below control levels during the following growing season. During the 2012 growing season, 1 year after the burn, there were larger diurnal increases in iWUE in scorched trees than in controls that increased as temperature increased and water availability decreased. This response was due to greater diurnal reductions in gs in scorched trees.