Figure 4

Relationship between summer Palmer Drought Severity Index and relative fire extent between 1648 and 1893 in the Rincon Peak in southeastern Arizona. (a) Diamonds represent widespread fires (i.e., years when ≥70 % of recording plots were scarred), circles represent fire years that scarred plots in the northern part of the study area and squares represent fires years that scarred plots in the southern part. Superposed epoch analysis (SEA) revealed that (b) widespread fire years were significantly drier than normal and preceded by unusually wet conditions 2 yr to 3 yr prior while (c) local fire years were also dry, but were not preceded by wet conditions. Confidence intervals determined from Monte Carlo re-sampling procedure.