Mediterranean -Type Ecosystem
15
1.2.5
Litter Production and Decomposition
It is generally accepted that the soils in Mediterranean-type ecosystems are
nutrient deprived (e.g. Specht and Moll 1983). Litter decomposition as well as
the dynamics of nutrient recycling are therefore of crucial importance for
their maintenance. The leaves of evergreen shrubs are small, hard and rigid,
containing tannins in their epidermis, while at the onset of the dry period, the
softer winter leaves of phryganic plants are replaced by smaller leaves rich in
sap content. In general, fallen litters are rich in non-easily decomposing
materials such as lignins and tannins (Read and Mitchell 1983; Iatrou 1989).
General information relevant to the composition of litter is supplied by Mooney (1977), while specific information is provided by Maggs and Pearson
(1977a), Mitchell et al. (1986), Tsiourlis (1990), and Papatheodorou (1996).
Dead leaves are most numerous among the contents of litter (over 60%), followed by dead wood (about 10%), while the proportion of fruits is almost
negligible.
Litter production is relatively high in relation to the total above-ground
biomass. In maquis it is continuous, displaying annual or 6 month periodicity (Margaris 1976; Lamotte and Bladin 1989; Tsiourlis 1990; Argyropoulou et
al. 1993). In some extreme Mediterranean environments, though, litter production is confined to short periods (Stamou et al. 1994). According to Tsiourlis (1990), a main peak of litterfall occurs in late spring/early summer and
characterises Mediterranean-type formations. In many cases the litterfall rate
has been correlated with soil water content, litter water content, evapotranspiration and photoperiodism (Specht and Rayson 1957; Maggs and Pearson
1977a; Nilsen and Muller 1981; Radea 1989).
Reabsorption of nutrients such as Nand P before litterfall is considered to
be an adaptation of Mediterranean plants growing in nutrient limited soils
(Maggs and Pearson 1977b; Fouseki and Margaris 1981; Read and Mitchell
1983; Papatheodorou 1996) resulting in an increasing C/N ratio. Increased
C/N ratio coupled with the increased lignin content of falling leaves results in
a reduced decomposition rate (Stamatiadis and Dindal 1990). In general,
annual decomposition rates range from 10 to 40% (Lossaint and Rapp 1971;
Yeilding 1977; Fouseki 1979; Tsiourlis 1990; Argyropoulou et al. 1993). Finally, it is noticeable that decomposition rates and soil microbial activities follow seasonal oscillations in temperature and humidity, thus synchronising
with plant growth demands (Fouseki 1979; Stamou et al. 1994).
15
1.2.5
Litter Production and Decomposition
It is generally accepted that the soils in Mediterranean-type ecosystems are
nutrient deprived (e.g. Specht and Moll 1983). Litter decomposition as well as
the dynamics of nutrient recycling are therefore of crucial importance for
their maintenance. The leaves of evergreen shrubs are small, hard and rigid,
containing tannins in their epidermis, while at the onset of the dry period, the
softer winter leaves of phryganic plants are replaced by smaller leaves rich in
sap content. In general, fallen litters are rich in non-easily decomposing
materials such as lignins and tannins (Read and Mitchell 1983; Iatrou 1989).
General information relevant to the composition of litter is supplied by Mooney (1977), while specific information is provided by Maggs and Pearson
(1977a), Mitchell et al. (1986), Tsiourlis (1990), and Papatheodorou (1996).
Dead leaves are most numerous among the contents of litter (over 60%), followed by dead wood (about 10%), while the proportion of fruits is almost
negligible.
Litter production is relatively high in relation to the total above-ground
biomass. In maquis it is continuous, displaying annual or 6 month periodicity (Margaris 1976; Lamotte and Bladin 1989; Tsiourlis 1990; Argyropoulou et
al. 1993). In some extreme Mediterranean environments, though, litter production is confined to short periods (Stamou et al. 1994). According to Tsiourlis (1990), a main peak of litterfall occurs in late spring/early summer and
characterises Mediterranean-type formations. In many cases the litterfall rate
has been correlated with soil water content, litter water content, evapotranspiration and photoperiodism (Specht and Rayson 1957; Maggs and Pearson
1977a; Nilsen and Muller 1981; Radea 1989).
Reabsorption of nutrients such as Nand P before litterfall is considered to
be an adaptation of Mediterranean plants growing in nutrient limited soils
(Maggs and Pearson 1977b; Fouseki and Margaris 1981; Read and Mitchell
1983; Papatheodorou 1996) resulting in an increasing C/N ratio. Increased
C/N ratio coupled with the increased lignin content of falling leaves results in
a reduced decomposition rate (Stamatiadis and Dindal 1990). In general,
annual decomposition rates range from 10 to 40% (Lossaint and Rapp 1971;
Yeilding 1977; Fouseki 1979; Tsiourlis 1990; Argyropoulou et al. 1993). Finally, it is noticeable that decomposition rates and soil microbial activities follow seasonal oscillations in temperature and humidity, thus synchronising
with plant growth demands (Fouseki 1979; Stamou et al. 1994).