Document: AND-3-68-21
Arizona pine stand dynamics: Local and regional factors in a fire-prone Madrean gallery forest.
BARTON, A.M.* 1, T.W.SWETNAM 2 and C.H.BAISAN 2
University of Maine at Farmington, Farmington, ME 04938 USA 1
University of Arizona, Tucson, AZ USA 2
Abstract:
In southwest North America, large-scale synoptic climate patterns exert control on moisture availability, fire occurrence, and tree demography, raising the compelling possibility of regional synchronization of forest dynamics. Such regional signals may, however, be obscured by local, site-specific factors. We examined Arizona pine (Pinus arizonica) in lower and middle Rhyolite Canyon, Arizona, contiguous sites with similar physical environment. Fire history was similar in the two sites from 1660-1801, but then diverged, possibly as a result of a local flood. We related stand dynamics to fire history and drought severity and compared the two sites before and after the divergence in fire frequency. Arizona pine exhibited three age structure peaks: two (1810-1830 and 1870-1900) shared by the two sites and one (1610-1640) only in middle Rhyolite. The latter two peaks occurred during periods of unusually low fire frequency, suggesting that fire-induced mortality shapes age structure. Evidence was mixed for the role of favorable moisture availability in age structure. Moisture availability had a prominent positive effect on radial growth, whereas the effect of fire was largely neutral. The two sites differed only moderately in stand dynamics during the period of divergence, exhibiting subtle age structure contrasts and, in middle Rhyolite only, reduced growth during a 49-year fire hiatus followed by fire-induced release. These results suggest that, despite local differences in disturbance history, forest responses to regional processes persist.
Keywords: Arizona pine, fire, drought severity, stand dynamics, age structure, radial growth, dendrochronology
This abstract is being presented at: 1:15 PM in session:
Oral Session #35: Fire Ecology.