Current-year flush and needle development in longleaf pine saplings after a dormant season prescribed fire

A longleaf pine (Pinus palustris Mill.) field performance study was established in central Louisiana in 2004. The study has received three prescribed burns (February 2006, May 2009, and February 2012) since establishment. In late April 2012, 35 saplings were selected and classified based on ocular estimates of needle mass scorch percentages. Mean needle scorch percentages for the lightly (LS), moderately (MS), and severely scorched (SS) saplings were 17, 50, and 99 percent, respectively. The prescribed fire did not change the temporal development of all flushes and their needles. However, the first three flushes of the SS saplings were significantly shorter than those of the LS saplings. The fourth and fifth flushes did not differ in lengths among scorch classes. Compared to flushes developed in 2011, which was a severe drought year, flush growth in the SS saplings was less in the fire year. Needles from the first SS flushes extended faster than those from the LS and MS saplings in May. Final needle lengths for the first and fourth flushes were not different among scorch classes whereas needles of the second and third SS flushes were shorter than those of less-scorched saplings. The physiological parameters, such as photosynthesis, stomatal conductance, and chlorophyll content, generally did not vary among scorch classes in August and September. However, these parameters were greater for the first SS flush needles than those of less-scorched saplings. The possibility of residual impact from prescribed fire on sapling growth in a subsequent year is discussed.