J. Ruiz del Castillo et al. / Invest Agrar: Sist Recur For (2006) Fuera de serie, 24-39
cover compared to the optimal state that the environ- ment allows: the most mature community according to site conditions. Thus, the EL is maturity degree as well. It has a positive correlation with the hydrological protection role of the plant cover, with stability and with biomass accumulation.
A combination of structural and floristic criteria make possible to assess the EL of a certain patch of vegetation, assigning a number according to its dis- tance from a theoretical desert. The numeric value increase from 0 (desert or complete absence of vegeta- tion) until 9 (highest complexity). CST involving the most severe climatic conditions (High Mountain and Hyperxerophile) have a lower width of variation, between
and 7; intrazonal vegetation can fluctuate between 0
and 6. An indicative outline of the EL according to examples of vegetation units is shown in Figure 7.
The characterization of most mature plant commu- nities has been carried out taking into account more than just theoretical considerations, but also a collec- tion of examples of relict patches. In CST where forests can occur, the highest EL corresponds to multispecific, dense forests with several layers (except for the peninsular Hyperxerophile, better simbolized by sparse pine forests of Pinus halepensis). In intrazonal types, scenarios are more diverse and complex, i.e. Glicohi- drophile most developed patches are multispecific forest along riverbanks whilst monospecific grasslands
Dense multispecific forest
Dense oligospecific forest
Dense monospecific forest
Dense high mixed coppice forest Pine forest with dense understorey
Dense small mixed coppice forest Oligospecific thorn scrub Pine forest with dense understorey, etc.
Dense scrub Monospecific thorn scrub Young reforested woodsstands
Clear scrub, Incipient reafforestation, etc.
Dward scrub, generally communities dominated by Labiatae, Compositae, etc.
Figure 7. Scale of relationships between evolution levels and examples of plant communities.