Chaparral is a fire-prone shrubland ecosystem dominant throughout the mediterranean-climate region of California. Postfire recovery has been well studied in California but this shrubland occurs also in disjunct patches of central and southern Arizona, where it ranges from bimodal rainfall to largely summer rainfall. This study investigates the similarities and differences between postfire recovery in these two regions.

Results/Conclusions

Many of the major characteristis of postfire recovery are shared between California and Arizona. In particular, the recovery of dominant species through both seedlings and resprouts. Also, both regions have an ephemeral flora of species unique to the postfire environment. These regions are markedly different, however, in several important respects. The herbaceous floras are rather different with C4 perennial grasses forming an important part of the postfire response in Arizona but this growth form is lacking in California chaparral. Due to the bimodal rainfall pattern, Arizona chaparral has two growth periods, one following summer rains and one following winter rains. California only has a spring growing season. Diversity in California chaparral is extraordinarily high in the first spring following fire, largely from annuals that arise from dormant seed banks. Arizona has a rich annual flora that comes from a dormant seed bank but this region has two somewhat different annual floras, one in the fall and one in the spring. When the total annual diversity is considered, postfire Arizona chaparral has one of the most diverse floras on record. We conclude that although California and Arizona chaparral share many of the same dominant shrub species, they comprise very different plant communities. This should be of interest to paleoecologists, since most assessments of past climates and community similarity are based on degree of similarity in macrofossils, which are usually from woody plants.