Sheep and goat summer grazing impact on plant species composition and diversity of an open Kermes oak shrubland

Shrublands occupy an area of 3,1 million hectares in Greece and contribute substantially to feeding of grazing animals. One of the economically important evergreen shrublands is that of kermes oak (Quercus coccifera L). Kermes oak shrublands provide green and of relatively high quality foliage to grazing animals almost all year-round. They are mainly grazed by goats and secondly by sheep. The objective of the study was to evaluate the impact of 1) goat, 2) sheep and 3) mixed moderate summer grazing on species composition and plant diversity of an open kermes oak shrubland. The research was conducted in Chrysopigi, Serres, north Greece, at 650m altitude and a subhumid climate. The experimental area of 21 ha open kermes oak shrubland was divided into six 3,5 ha each, equal size plots. A completely randomized design was applied for the three treatments: 1) goat grazing, 2) sheep grazing and 3) mixed sheep and goat grazing. All treatments were repeated twice. Vegetation parameters were measured at the end of May for three consecutive years (1997, 1998 and 1999). Measurements of 1997 were considered as reference data. The number of grazing animals was equal to grazing capacity of every plot. Plant species composition was measured using the line point method. Species richness and species abundance were measured in 0,5x 0,5 m quadrates. Then, plant diversity was calculated using the Shannon-Wiener (H) diversity index. Species composition for all grazing treatments varied through the years according to precipitation’s fluctuation and to grazing treatment. Plant diversity increased but not significantly, by 33,8% for goats, 5,4% for sheep and 15,4% for the mixed treatment through the years (1997-1999).