Climate and hydrology - Mediterranean Mountain Environments - page 86

Figure 5.1 Mediterranean mountain river basins (including mountain ranges on mainland and
islands) of pilot sites corresponding to Table 5.2. ( A full colour version of this figure appears in
the colour plate section )

river regimes. Depending on altitude, some of these are dominated by snowmelt,
others are purely rainfed. Snowmelt discharge regimes are generally more reliable,
in particular where snow acts as a buffer and releases run-off with a delay in spring-
time. Nevertheless, snowmelt volumes are influenced by temperature (Cazori and
Dalla Fontana, 1996) and can be restricted by sublimation. Relationships between
rainfall run-off regimes are not always simple either, especially at the catchment
level, where evapotranspiration can have important influences (Latron et al., 2008).
The seasonal temperature evolution in Mediterranean regions has a direct effect on
evapotranspiration dynamics, which, in combination with the seasonal dynamics of
rainfall, cause the succession of wet and dry or very dry periods during the year
(Latron et al., 2009). This seasonality of the Mediterranean mountain climate has a

Table 5.1 Classification of Mediterranean vegetation levels and equivalent thermal thresholds.
After Akman and Daget (1971), Ozenda (1975), Quezel (1976), Peyre (1979), and Rhanem
(2008)

Thermal limits ( ◦ C)

Vegetation and thermal thresholds Classification

Oro-Mediterranean

− 15

Glacial

− 15 to − 12 Extremely cold

− 12 to − 9
− 9to − 6

Mountain Mediterranean − 6to − 3 Very cold

Superior and supra-Mediterranean − 3to0 Cold

Meso-Mediterranean 0 3 Cool

Thermo-Mediterranean 3 to 7 Temperate

7to10 Hot

10 Very hot