Consequences of seasonal fires on the structure and function of eastern Mediterranean woodlands

Seasonal fires can have important consequences on forest dynamics, owing to their differential effects on soil microorganisms as well as on plant species adopting different regeneration strategies: vegetative growth (i.e., resprouters) versus seed germination (i.e., seeders). I report here the results of a large-scale field experiment, involving prescribed spring and autumn burns, conducted for the first time in a Mediterranean woodland in Israel. Although fire intensity and severity were consistent between the two seasonal fires, the community composition of both soil fungi and perennial plants differed between areas subjected to spring and autumn burns. Changes in the soil fungal community were driven mostly by modifications occurring within the saprotrophic fungal guild. Such alternations often directly influence both decomposition rate and carbon emission, thus having important implications for ecosystem functioning. Differential fire season effects were also detected among obligate seeders, which experienced stronger reductions in their abundances after spring than after autumn burns. The implications of these findings for conservation and management of eastern Mediterranean woodlands are as follows: 1) Maintaining biodiversity in this unique ecosystem requires promoting spatial variability in seasonal fires, i.e., increased pyrodiversity. 2) Since perennial seeders are more flammable than resprouters, spring burns can be used to effectively reduce the flammability of the live vegetation in fire breaks and buffer zones.