Mediterranean-Type Ecosystem
2.0
1.6
~ ....
~
.... 1.2
;<;::
~ _ 0.8
r:
i
Vl 0.4
3
O.OL-------~------~------~------~------~-0.0
0.1
0.2
0.3
0.4
0.5
Frequency (cycles/a)
Fig. 1.2. Periodogram analysis of Emberger's pluviometric index estimated for the period
1946-1984 (Data from Iatrou 1989)
matoral (Chile), chaparral (California), fynbos (South Africa), and mallee
(Australia). The dry end point of the Mediterranean humidity gradient is
occupied by formations dominated by seasonally dimorphic, drought deciduous shrubs. These formations are known in Greece as phrygana, in Israel as
batha, in Spain as tomillares, in California as coastal sages, and in South
Africa as renosterbos (Margaris 1981).
Mediterranean-type ecosystems appear to be highly heterogeneous in the
course of time and spatially fragmented, which and this is considered highly
characteristic. Periodic heterogeneity stems from interannual, seasonal and
diurnal sources of variability in temperature and humidity. Figure 1.2 shows
the results of a periodogram analysis applied to data concerning temperature and precipitation combined in Eberger's pluviometric quotient. Data were
gathered over a period of 40 years in the city of Thessaloniki. The graph displays a clear-cut peak at a frequency of 0.25, meaning interannual periodicity of 4 years. Analogous interannual patterns have also been reported for
most other Mediterranean regions (e.g. Petanidou 1991). In addition to regular interannual climatic fluctuations, broad seasonal fluctuations in climatic
variables is another characteristic of Mediterranean climates. For example,
seasonal fluctuations of temperature exceeding 55°C coupled with water content variations in the range of 10-60% are commonly recorded in the upper
soil layers. Quite frequently, the seasonal variation in air temperature exceeds
55°C, and the dry period persists for more than half a year. Figure 1.3 shows
the ombrothermic graph for an asphodel desert in Thessaly. Air temperature
varied from 0 to 50°C, while the dry period lasted for 6 months in the first
year and 8 months in the second. Pronounced oscillations in solar radiation
2.0
1.6
~ ....
~
.... 1.2
;<;::
~ _ 0.8
r:
i
Vl 0.4
3
O.OL-------~------~------~------~------~-0.0
0.1
0.2
0.3
0.4
0.5
Frequency (cycles/a)
Fig. 1.2. Periodogram analysis of Emberger's pluviometric index estimated for the period
1946-1984 (Data from Iatrou 1989)
matoral (Chile), chaparral (California), fynbos (South Africa), and mallee
(Australia). The dry end point of the Mediterranean humidity gradient is
occupied by formations dominated by seasonally dimorphic, drought deciduous shrubs. These formations are known in Greece as phrygana, in Israel as
batha, in Spain as tomillares, in California as coastal sages, and in South
Africa as renosterbos (Margaris 1981).
Mediterranean-type ecosystems appear to be highly heterogeneous in the
course of time and spatially fragmented, which and this is considered highly
characteristic. Periodic heterogeneity stems from interannual, seasonal and
diurnal sources of variability in temperature and humidity. Figure 1.2 shows
the results of a periodogram analysis applied to data concerning temperature and precipitation combined in Eberger's pluviometric quotient. Data were
gathered over a period of 40 years in the city of Thessaloniki. The graph displays a clear-cut peak at a frequency of 0.25, meaning interannual periodicity of 4 years. Analogous interannual patterns have also been reported for
most other Mediterranean regions (e.g. Petanidou 1991). In addition to regular interannual climatic fluctuations, broad seasonal fluctuations in climatic
variables is another characteristic of Mediterranean climates. For example,
seasonal fluctuations of temperature exceeding 55°C coupled with water content variations in the range of 10-60% are commonly recorded in the upper
soil layers. Quite frequently, the seasonal variation in air temperature exceeds
55°C, and the dry period persists for more than half a year. Figure 1.3 shows
the ombrothermic graph for an asphodel desert in Thessaly. Air temperature
varied from 0 to 50°C, while the dry period lasted for 6 months in the first
year and 8 months in the second. Pronounced oscillations in solar radiation