Comparison of post-®re seedling establishment between scrub communities in mediterranean and non- mediterranean climate ecosystems

1 Both ®re regimes and the conditions under which ®res occur vary widely. Abiotic conditions (such as climate) in combination with ®re season, frequency and intensity could in ̄uence vegetation responses to ®re. A variety of adaptations facilitate post-®re recruitment in mediterranean climate ecosystems, but responses of other communities are less well known. We evaluated the importance of climate by comparing sites with mediterranean and subtropical climates. 2 We used paired burned and mature sites in chamise chaparral, mixed chaparral and coastal sage scrub (California), and rosemary scrub, sand pine scrub and sandhill (Florida), to test whether (i) patterns of pre-®re and post-®re seedling recruitment are more similar between communities within a region than between regions, and (ii) post-®re stimulation of seedling establishment is greater in regions with marked ®re-induced contrasts in abiotic site characteristics. 3 Post-®re seedling densities were more similar among sites within climatic regions than between regions. Both seedling densities and proportions of species represented by seedlings after ®res were generally higher in California. 4 The only site characteristic showing a pre-®re±post-®re contrast was percentage open canopy, and the e€ect was greater in California than in Florida. Soil properties were una€ected by ®re. 5 Mediterranean climate ecosystems in other regions have nutrient-poor soils similar to our subtropical Florida sites, but show post-®re seedling recruitment patterns more similar to the nutrient-rich sites in California. Climate therefore appears to play a more major role than soil characteristics.