Abstract:
Global climate change has put an increased focus on enhancing adaptation potential of forest ecosystems. It is hypothesized that structurally complex stands exhibit greater resistance and resilience to stresses. An underutilized component of structural complexity is the spatial arrangement of trees within a stand. In ecosystems where tree species diversity is low, such as longleaf pine (Pinus palustris Mill.) ecosystems, it is critical to maximize spatial heterogeneity to increase structural complexity. These ecosystems cover less than 1 million ha of their previous 37 million ha range and are among the most endangered in the U.S. To increase the effectiveness of management plans within P. palustris ecosystems, we examined spatial patterns within a P. palustris woodland stand within the Oakmulgee Ranger District of the Talladega National Forest, Hale County, Alabama. We specifically asked (1) how were trees distributed in this stand? (2) Are trees clumped, dispersed, or randomly distributed? (3) What spatial relationships exist between mature trees and P. palustris saplings? Using an individuals, clumps, and openings method, we determined most trees existed in clumps beginning at an intertree distance threshold of 3 m. At an intertree distance of 6 m, half of all trees were in clumps of 10 or more. Trees were significantly (p < 0.05) clustered by age and diameter (up to 20 cm diameter at breast height). Pinus palustris saplings were clustered around canopy P. palustris beginning at a distance of 16 m and around Quercus laevis trees beginning at a distance of 7 m. Managers can increase structural complexity (and therefore ecosystem resistance and resilience) by modeling silvicultural prescriptions after the effects of natural disturbance with concrete reference spatial patterns.
