Ph.D Thesis

Ph.D StudentBlank Lior
SubjectMultiscale Analysis of Species Distribution Pattern
DepartmentDepartment of Civil and Environmental Engineering
Supervisor PROF. Yohay Carmel
Full Thesis textFull thesis text - English Version


Understanding the factors regulating the distribution of species is one of the greatest challenges of ecology. Studies of species distribution patterns and of correlations between species and environmental factors overlooked woody vegetation as an important factor. In terms of their effects on species composition and richness, woody plants can be considered as dominant factors which extensively affect their environment, changing resource distribution in space and time. In this study I investigated the role of woody vegetation in affecting the distribution of herbaceous species .

There is an increasing recognition that different types of ecological processes are important drivers at different scales. Multi-scaled studies can provide important insights for conservation management. In order to study biodiversity at multiple scales, I planned a hierarchically nested sampling design that is balanced across scales. Using this sampling scheme I recorded vascular plants. In order to assess the relationships between species diversity and various environmental variables, I also conducted an extensive soil sampling and using remote sensing I characterized the spatial pattern of the woody vegetation. Using advanced statistical methods I was able to address the following questions :

The first research question focused on evaluating the role of fine scale effect of specific woody species patch types in determining herbaceous species distribution, community properties and the relative frequency of various functional groups. The second research question explored the effects of scale on the functioning of communities, and attempted to identify the environmental factors most highly correlated with species richness and composition at different scales . The third research question dealt with the effects of spatial configuration and landscape heterogeneity on species richness at different scales. It is important to know whether the processes that determine community structure are indifferent to the scale of observation.

            My finding revealed that viewing ecological systems as composed of woody and non-woody patches is rather simplistic. I believe that in heterogeneous ecosystems such as Mediterranean ecosystems, accounting for specific woody species patch types may largely enhance our understanding of plant community structure. In addition, I found that woody vegetation is an important element in controlling the spatial distribution of species across scales.

I present evidence for scale-dependence in the relations between woody vegetation and herbaceous species richness. I propose a mechanism that may explain most of the observed scale-dependent responses. Together, the three components of this work enhance our understanding of the study of species distribution and its scale dependence.