Ph.D Thesis

Ph.D StudentBar Massada Avi
SubjectMapping and Modeling the Dynamics of Mediterranean
Vegetation under Various Management Activities
DepartmentDepartment of Civil and Environmental Engineering
Supervisor PROF. Yohay Carmel
Full Thesis textFull thesis text - English Version


The eastern Mediterranean region has been subjected to intensive human disturbance in the past 10,000 years, mainly by grazing, shrub clearing, and burning. This disturbance history created highly heterogeneous landscapes, supporting high biodiversity. Recent changes in human activities decreased landscape heterogeneity, leading to decreasing biodiversity and increasing fire risk. To conserve heterogeneity, land managers apply disturbance based management practices, using the same activities that created and maintained it in the past. However, the long-term and large-scale outcomes of these disturbances are often unknown. In this research, the effects of disturbances on the spatio-temporal dynamics of vegetation in Mediterranean landscapes were studied.

The major component of the research was the development of a spatially explicit dynamic ecological model, in attempt to predict the outcome of management activities on the spatio-temporal dynamics of five Mediterranean vegetation types. The model uses a spatially explicit state-and transition formulation with continuous transition functions. Model simulations were conducted on two types of landscapes, random-generated and actual, and incorporating various disturbance practices. Simulation results highlight the potential of disturbance based management as a tool for conserving landscape heterogeneity, as well as the complex interactions between disturbances and the spatial structure of the landscape.

            Spatially explicit models require vegetation maps in order to be applied on actual landscapes. Mapping Mediterranean vegetation is complex, due to its fine scale heterogeneity, coupled with the high spectral similarity of many woody species. Here, a novel mapping approach was developed, based on data fusion of LiDAR and aerial photography. A continuous map of height and woody cover was created, and then categorized in order to generate the required vegetation map that serves as the input for the model.

            Another research component was empirical quantification of the effects of goat grazing and shrub clearing on the fine scale spatial structure of woody vegetation. The outcomes of a large scale field experiment were mapped using low altitude aerial photography. Landscape metrics were successfully employed here to quantify the very fine scale structure of vegetation following disturbances.

            Together, the three components of this work enhanced the understanding, methodology, and predictive capability of the outcomes of disturbance based management on the structure, configuration, and composition of a Mediterranean landscape at various spatial and temporal scales. This field of research is becoming increasingly important due to the wide-spread land-use and land-cover changes in the region, that can be moderated and controlled through disturbance based management.