| Ecotones and edges are of interest because they usually show particular properties such as increase of abundance, diversity, or primary productivity, which are attractive for management purposes and conservation biology. Recently, however, with the increase of forest fragmentation, the frequency of edges and ecotones has increased, causing a potential increase in predation, parasitism and species competition. The impacts of the increase in length of ecotones, their dynamics, and their impacts on biodiversity need to be identified.; Up to the present, however, only qualitative definitions of ecotones are available, such as "transition zones between communities". Indeed, although ecotones are found in terrestrial landscapes at several scales of observation, they remain not clearly defined both theoretically and operationally. Methodological studies are therefore needed to establish an operationally definition of ecotones.; After defining an ecotone quantitatively as contiguous locations of high rates of change, I investigated how edge detection methods and subgraph statistics can be employed to identify the locations of potential ecotones. These investigations were carried out using simulated data and actual tree vegetation data sets from two temperate areas: the Weld forest (New York), and the forest of the Haut-Saint-Laurent (Quebec). With these data sets, I tested whether the detection of ecotones is consistent when different scales of observation (quadrat sizes), different variable types (density, percent-coverage, and presence/absence data), and species assemblages (herbs, shrubs, and trees) are employed.; In static cases, the edge detection algorithms and significance tests based on subgraph statistics have been found useful to delimit potential ecotones. Given that significant rates of change can be identified, optimal sampling designs in the field can be established to study and monitor the functional properties of ecotones. |
