PARENT SESSION
Oral Session 8: Forest Ecology I: Dynamics and Succession.
Presiding: A Fiala and D Kashian
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room B 117.

Applicability of boundary-line release criteria to North American tree species.

Black, Bryan¹, Abrams, Marc², ¹ Hatfield Marine Science Center, Newport, OR² Penn State University, University Park, PA

ABSTRACT- Identifying releases from suppression represents one of the most fundamental dendroecological procedures for estimating forest disturbance histories. We demonstrate the potentially widespread application of new release criteria that incorporate the effects of prior growth on percent-growth change pulses following a disturbance. Prior growth is defined as average ring width over the past ten years, and percent growth change is defined as percent difference between prior and subsequent 10-yr ring-width means. We show that in Pinus strobus, Pinus echinata, Pinus ponderosa, Picea glauca, Picea mariana, Quercus prinus, Quercus alba, Quercus macrocarpa, Quercus stellata, Tsuga canadensis and Pseudotsuga menziesii, maximum percent-growth change declines at a negative exponential rate as prior growth levels increase. This negative exponential boundary represents the maximum percent-growth change that is physiologically possible at a given level of prior growth. Prior-growth boundary lines are unique for each species, indicating species-specific differences in the magnitude of radial growth pulses following disturbance. We then use these boundary lines to scale each growth pulse as a percentage of its maximum possible value, given the tree species and rate of prior-growth. Scaling each growth pulse to the boundary line compensates for species-specific differences in release response and the effects of prior growth. If all releases are expressed in terms of their maximum potential, direct comparisons could be more readily made within and between stands to estimate landscape-level patterns of disturbance.

Key words: release criteria, dendroecology, disturbance history