Persistence of a pine tree with mixed fire-adapted life history strategy in subtropical spring fire-prone habitats

Abstract

Whether pines can cope with fire depends on either species persistence or individual survival. Pinus yunnanensis is the most widely distributed endemic species in Southwest China, and is well adapted to fire with a mixed fire-adapted strategy of post-fire regeneration and fire resistance. However, whether its regeneration depends on fire disturbances is unclear. We reconstructed the fire history of a P. yunnanensis forest in Yunlong Tianchi National Nature Reserve over the past 100 years using fire scars and forest age structures to determine relationships between historical fires and recruitments. Additionally, post-fire regeneration processes of three burned patches were examined to explore P. yunnanensis dynamics after fires. The P. yunnanensis population in the Reserve had a “discontinuous multi-cohort” structure. There was a 6–16 year gap between cohorts, and each cohort comprised individuals that differed by 1–7 years. The study area experienced seven fires in the past 100 years, with an average interval of about 12 years, with surviving individuals in every fire. These historical fires align with P. yunnanensis cohorts emergence. Post-fire P. yunnanensis regeneration in the burned patches mainly occurred in the first two rainy seasons after the fire, then the number of new individuals significantly dropped and remained very low from the fourth year onward. P. yunnanensis population structure has undergone a shift following the enforcement of a fire suppression policy. Some P. yunnanensis adults appear able to survive low to moderate severity fires, and the population could achieve post fire functional recruitment, thus maintaining a “discontinuous multi-cohort” structure in fire-prone habitats as a result of a mixed fire-adapted strategy. Recurrent fire is the key driving factor in maintaining the long-term persistence of pure P. yunnanensis forests.