Vegetation structure and biodiversity in Mediterranean ecosystems: A comparative study from Lebanon and California.
Atallah, Youssef*,1, Bocker, Reinhard1, 1 University of Hohenheim, Stuttgart, Germany
ABSTRACT- The Mediterranean type ecosystems in Lebanon and California were compared to investigate the distribution of plant communities along the altitudinal gradient. Comparable climates and nutrient poor soils appear to produce similar ecosystems in both regions. The Mediterranean plant growth forms and vegetation formations are thought to be the result of convergent evolution. Meanwhile the physiognomies of various herbs, shrubs and trees dominated vegetation are similar in both regions, whereas the underlying floras are quite distinct. There is little evidence supporting the convergent evolution theory at community level on different continents. Life form spectra of the two mediterranean floras also show large differences. California has significantly smaller fractions of therophytes and geophytes but larger fractions of chamaephytes, shrubs and trees. Shrubs multistem trees with evergreen sclerophyllous leaves dominate California chaparral and Lebanese maquis, however, the details of canopy structure are different. Chaparral is generally 1-3 m tall with a closed canopy; it is essentially one-stratum vegetation with an absence of herbaceous elements beneath the evergreen canopy. On the other hand the maquis canopy generally averages 4-5 m in height and is frequently open. There is a spring peak in community flowering in both Mediterranean regions. There are no obvious differences in flowering patterns between communities on different elevations and soil nutrient contents, and this can perhaps be attributed to predominance of insect pollinated species in Lebanon and California. Disturbance has not only contributed to biological diversity of Mediterranean plant communities but also to their composition, structure and niche differentiation.
Key words: Mediterranean ecosystem comparison, Plant community change with elevation, Disturbance, Plant survey, California, Lebanon
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