Tree regeneration dynamics under a range of restoration treatments in Northeast pitch pine (Pinus rigida) barrens

Abstract

Fire suppression and disconnection from historic fire regimes has a distinct and significant impact on fire-dependent natural communities, including regeneration of characteristic species, whose restoration may be further complicated by climate change. Pitch pine (Pinus rigida) barrens are a globally rare, fire-dependent natural community found primarily in the Northeast United States. We analyzed pitch pine regeneration response across 47 sites treated with 1) harvest (n = 6), 2) fall prescribed fire (n = 9), 3) spring prescribed fire (n = 9), 4) mowing followed by prescribed fire (n = 12), and 5) controls (n = 11), in barrens across the Northeast, to measure the impacts of regionally common restoration treatments on desired regeneration success. Leaf litter depth, mineral soil exposure, overstory basal area and composition, understory plant cover, and tree regeneration in three size classes across these five treatment types were compared. Pitch pine small seedling abundance was adversely impacted by greater litter depth, understory cover, and abundance of shrub oak (Quercus ilicifolia and Quercus prinoides) seedlings. All treatment types had significantly more small seedlings than untreated control units. Large seedling abundance was also negatively associated with increased litter depth. Pitch pine sapling abundance increased with pitch pine overstory proportional abundance and decreased as shrub oak saplings increased. This study represents the first multi-region assessment of pitch pine restoration treatments, confirming necessary conditions for pitch pine regeneration established by previous site-level work. While no single management strategy emerged as most effective, conditions resulting from higher severity disturbances appear more conducive to pitch pine regeneration establishment and provide managers with several options to maintain these ecosystems.