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Tuesday, April 10 • 11:00am - 11:15am
DISTURBANCE LEGACIES AND RESILIENCE: Spatial Variability in Tree Regeneration and Potential Fire-Driven Range Shifts at a Dry Forest Ecotone

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AUTHORS: Lucas Harris, Alan H. Taylor – Pennsylvania State University

ABSTRACT: Future change in dry forest systems is likely to be abrupt and nonlinear, with severe disturbancepotentially causing persistent changes in vegetation types. A gridded network of field plots spaced 90 m apart (n = 439) was surveyed at five sites at the lower-elevation forest ecotone on the east side of the Sierra Nevada, California, in areas burned between 2002 and 2008 to evaluate post-fire tree regeneration and to characterize the influence of local topography, water balance and vegetation on post-fire forest recovery. Each site encompassed the elevational range of Jeffrey pine (Pinus jeffreyi) forest from shrub steppe and pinyon pine-dominated (Pinus monophylla) woodland at the downslope end to mixed-conifer forest at the upslope end, with areas of Cercocarpus ledifolius interspersed. Plots where all trees were killed by the fire and no seedlings or saplings were present were characterized by lower actual evapotranspiration, more southwesterly aspects, more gradual slopes, less leaf litter and lower shrub cover than in corresponding areas where tree regeneration was present. Statistical modeling of tree regeneration presence by individual tree species and for all species combined revealed that the relative influence of topography, water balance and vegetation on tree regeneration varied by species, but that high actual evapotranspiration and nearby (< 15 m away) live trees were common factors that were critical for regeneration of each species. These results suggest that variability in water balance and local climate generated by complex terrain and vegetation structure affect post-fire tree regeneration, and that forest loss is likely to occur in drier and sparsely vegetated portions of the sites.

Tuesday April 10, 2018 11:00am - 11:15am CDT
Water Tower Parlor