Human-scale structural heterogeneity induced by grazing in a Mediterranean woodland landscape

A set of structural criteria to differentiate among types of a heterogeneous woodland landscape that are shaped by goat and cattle grazing was studied in northern Israel. The landscape was described with relation to the ‘‘human scale’’ of the observer, by mapping the dimensions, basic shapes, and distribution of gaps between individual plants on sites with various grazing management systems. The shapes of the trees and the bushes were drawn in situ and the ratio between plant height and the width of the adjacent open space was measured in order to define the various structural profiles of the vegetation. All the structural criteria clearly and significantly differentiated among grazing systems that created closed (no grazing), half-open (cattle and modern goat grazing) and open (traditional goat grazing) landscapes. The diversity of plant shapes was highest under the cattle and modern goat grazing management systems. In the ungrazed treatment, more than 60% of the gaps were defined as ‘inaccessible’ compared with only 10–15% under cattle grazing and modern goat grazing. The diversity of gap proportions was high, but their absolute number was low. Under traditional heavy goat grazing, there were only wide and open gaps. Under cattle grazing and modern goat-grazing management systems, a relatively large number of wide and open gaps were found, with small numbers of narrow and closed gaps. Overall, the various grazing systems were differentiated most clearly according to their transparency, accessibility, height of Quercus calliprinos, and gap distribution. We conclude that structural criteria provide an efficient and objective methodology for evaluating the effects of grazing on different components of Mediterranean woodland mosaic landscapes.