干旱区生态环境知识资源中心

Deep-rooted plants (phreatophytes) survive the Mediterranean dry season by utilizing rainfall accumulating belowground from past rainfall events. This adaptation potentially influences their moisture content when acting as living fuel for forest fires. Other shallow-rooted herbaceous plants (therophytes) survive drought as seeds, acting as very flammable fine fuel because their biomass totally desiccates in summer.

We investigated the effects that these ecological adaptations (functional-structural) may have in shaping the fire regime in the Mediterranean by: (a) separating precipitation (P) and temperature (T) to longer (entire hydrological year) and shorter (seasonal and monthly) temporal scales, (b) correlating the above with burnt area (BA) and number of fires (NF) from the thermo- and medio-Mediterranean vegetation belts (TMVB-MMVB; the most arid and flammable belts), (c) comparing correlations with those from regions of more moist climate and related vegetation. Spatial scales ranged from provinces of Greece and southern France, to combined data for Greece, Italy, France and Spain. We focused on 1985-2008 (and its sub periods); one of the driest periods for the Mediterranean, with large fire occurrence.

Clearly, where the TMVB-MMVB prevail P outweighs Tin determining BA, having a rather equal contribution in explaining NF. In the driest areas increased P accumulating from autumn, but mostly supplied in winter, suppressed BA the following summers, likely because it improved moisture content in pheatophytic vegetation (living fuel). This impact was reduced in more humid regions, where fires suppression was related to increased summer P that makes fuel damp. In contrast, increased late-spring P promoted BA and NF likely by increasing biomass accumulation from therophytic vegetation (fine fuel).

Indications for the resistance of pheatophytic plants to fire following wet winters are already evident in the recent fire regime of northern Mediterranean countries. This function may strengthen under a drier climate and could assist early fire-danger prognosis. (C) 2013 Elsevier B.V. All rights reserved.