The path back: oaks (Quercus spp.) facilitate longleaf pine (Pinus palustris) seedling establishment in xeric sites
Abstract
Understanding plant–plant facilitation is critical for predicting how plant community function will respond to changing disturbance and climate. In longleaf pine (Pinus palustris Mill.) ecosystems of the southeastern United States, understanding processes that affect pine reproduction is imperative for conservation efforts that aim to maintain ecosystem resilience across its wide geographic range and edaphic gradients. Variation in wildland fire and plant–plant interactions may be overlooked in “coarse filter” restoration management, where actions are often prescribed over a variety of ecological conditions with an assumed outcome. For example, hardwood reduction techniques are commonly deemed necessary for ecological restoration of longleaf pine ecosystems, as hardwoods are presumed competitors with longleaf pine seedlings. Natural regeneration dynamics are difficult to test experimentally given the infrequent and irregular mast seed events of the longleaf pine. Using a long‐term, large‐scale restoration experiment and a long‐term monitoring data site at Eglin Air Force Base, Florida (USA), this study explores the influence of native fire‐intolerant oaks on longleaf regeneration. We test for historical observations of hardwood facilitation against the null hypothesis of competitive exclusion. Our results provide evidence of hardwood facilitation on newly germinated longleaf pine seedlings (−1 were sufficient to facilitate seedling survival, but as many as 1400 stems ha−1 maintained facilitation without competitive exclusion of seedlings. We found that 1.5‐yr‐old pine seedlings were more moisture stressed under more open canopy conditions when compared to those immediately adjacent to a midstory oak canopy. Recognition that deciduous oaks are important facilitators of longleaf seedling establishment on xeric sites represents a significant departure from conventional wisdom and current management practices that has largely focused on competitive exclusion. This points to a critical role of a deciduous oak midstory of moderate densities for long‐term ecosystem resilience in xeric longleaf pine ecosystems in light of climate uncertainty.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jun 01, 2016
- Source ID
- 10.1002/ecs2.1361
Entities
People
- Analie Barnett
- E. Louise Loudermilk
- J. Kevin Hiers
- Joseph J. O'Brien
- Robert J Mitchell
- Scott Pokswinski
Organizations
- Strategic Environmental Research and Development Program
- The Jones Center at Ichauway
- The Nature Conservancy
- University of Nevada, Reno