Fire history along environmental gradients in the Sacramento Mountains, New Mexico: Influences of local patterns and regional processes

Patterning in fire regimes occurs at multiple spatiotemporal scales owing to differences in scaling of local and regional influences. Local fire occurrence and behavior may he controlled largely by site factors, while regional climate and changes in human land use can synchronize fire timing across large areas. We examined historical patterns in fires during the past five centuries across gradients in forest types and physiography and in relation to regional climate variability and land use change in the Sacramento Mountains in southern New Mexico. Forest stand-level chronologies of fires were reconstructed for 19 pinyon-juniper, ponderosa pine, and mixed-conifer stands using fire-scar records in crossdated tree-ring series. The fire history documents both local and regional factors effected fire occurrences in stands. Lower-elevation stands recorded more frequent fire than higher-elevation stands, although there were not significant differences between means of fire frequencies from clusters of ponderosa pine and mixed-conifer stands. Mean fire intervals ranged from approximately 3 to 11 years in ponderosa pine sites to 4 to 14 years in mixed-conifer sites. Sites on the steeper west side of the range, where fire spread more readily between forest types, recorded significantly more frequent fire than sites on the more physiographically heterogeneous east side. Fires were also synchronized by regional factors. Fire occurrences and fire-free years are related to variability in both annual Palmer Drought Severity Indices and El Nino-Southern Oscillation events. Fire regimes in the stands were also profoundly effected by changes in human land use patterns, with fire cessation in all sites following intensive Euro-American settlement beginning in the 1880s.