Longleaf pine adaptation to fire: is early height growth pattern critical to fire survival?This article is part of a larger document. View the larger document here.
Longleaf pine (Pinus palustris Mill.) forests are fire-dependent ecosystems because frequent surface fires prevent other species from being recruited into the canopy. The successful recruitment of longleaf pine has been attributed mainly to its unique fire adaptation – the grass stage. It is commonly believed that, while in the grass stage, longleaf pine seedlings build carbon reserves in the taproot, and this reserve is then mobilized to support fast height growth so that the apical meristem can quickly elevate above flame height. Based on this perception, we hypothesize that when longleaf pine emerges out of grass stage, (H1) height growth is a sudden process so that a critical threshold height can be reached quickly, and (H2) longleaf pine has faster height growth than its fire-susceptible co-genera, loblolly pine (P. taeda L.). To test H1, we examined early height growth patterns of planted longleaf pine seedlings. We found that height growth was a gradual rather than a “sudden” process, and there is no evidence for reaching a critical threshold value. To test H2, we conducted stem analysis for young longleaf and loblolly pine trees growing on the same sites. We found that longleaf pine, despite years in grass stage, did not grow any faster than loblolly pines when young. Our results suggest that the pattern and rate of height growth may not give longleaf pine any advantage for fire survival.