Assessment of Grazing Effect on Two Sub-Shrubs (Astragalus schottianus and Thymus sipyleus) Dominated Mountain Bozoğlan Grasslands in the Semi-Arid Central-Southern Anatolian Region of Turkey

摘要

In the central-southern Anatolian region of Turkey, vegetation of Mountain Bozoğlan grasslands has severely deteriorated, and two sub-shrubs (Astragalus schottianus and Thymus sipyleus) have become dominant species. We hypothesized that the spatial distribution of these dominant shrubs is closely associated with a long history of grazing, and these species might cause alteration of the grassland plant community. Therefore, our objectives were to determine: (1) the patterns in grassland vegetation; (2) how the dominant species contribute to these patterns; and (3) the differences of patterns between ungrazed and protected grassland areas. Plant cover in ungrazed plots was 6% higher than that of grazed plots. Total sub-shrub cover did not differ significantly, but grazing considerably reduced forbs (5% less) and grass cover (5% less). Though A. schottianus and T. sipyleus did not change between the treatments, Festuca valesiaca had greater cover in ungrazed areas (6%) than in that of grazed plots (3%). Grazing effect, soil properties and bare ground appeared to account for most of the variation on the established gradients. Even after 23 years, grazing and protection had little influence on pattern formation, and grazing have expanded dwarf-shrubs at the expense of forbs and grasses. Grazing neither increased nor decreased spatial heterogeneity, so the patterns in both treatments are similar to one another, and relatively stable assemblages of species were likely derived by high grazing pressure experienced before the exclosure establishment.