Modelling the effects of human activity on the vegetation of a northeast Mediterranean island

Question: Which factors affect the spatial variation of maquis and phryganic vegetation and how can the role of human activities be estimated through degradation models.

Location: Island of Sifnos, Cyclades, Greece.

Methods: Data on woody vegetation, environmental conditions and intensity of human activity were collected by field survey. The vegetation data were analysed using TWINSPAN. Models based on the combination of Canonical Variate Analysis and logistic regressions were used in order to examine and describe the different pathways of maquis degradation.

Results: The spatial variation of maquis and phryganic vegetation was related to both environmental and disturbance factors. The replacement of maquis by phryganic vegetation can follow two different pathways which reflect differences on the environmental conditions. However, the pathways themselves are determined by the combinations and levels of disturbance only.

Conclusion: Degradation models can provide essential information on the effects of human activities on the vegetation. Maquis vegetation is relatively tolerant of disturbance, however. if disturbance exceeds certain critical thresholds, maquis is replaced by phryganic vegetation. The presence of phryganic vegetation is not always the result of maquis degradation.