摘要：A noticeable decline of Quercus ithaburensis ssp. Macrolepis, a typical mediterranean species, has been recorded in the past few decades throughout Greece. The triggers were mostly human influences and specifically illegal cuttings, wildfires, and overgrazing. Regeneration and future management of this species is therefore questionable. To investigate the effect of companion plants on this decline as expressed by water availability and plant growth, a pot experiment was conducted and oak seedlings were planted with Bromus sterilis and a mixture of Trifolium repens and T. fragiferum as companion plants. Midday water potential from May to September and oak growth at the end of the experiment were measured as factors affecting oak physiology. The results suggest a different effect on the water potential of the oak seedlings depending on the companion plant species and the time of the year. The presence of a companion plant that has completed its life cycle by the end of spring may positively influence the water status of oaks during the summer months due to shading and lower soil water evaporation. On the contrary, when the companion plants continue their life cycle in the summer, the negative effect may be continued, specifically during the very dry months. The negative effect of grass on the growth of oaks may be attributed to their shading from the dense grass biomass. It can be concluded that control of competitive vegetation, especially of grasses, is crucial for Quercus ithaburensis ssp. macrolepis regeneration by natural (from acorns) or artificial (with up to one-year-old seedlings) methods. This control is necessary at least in the first year after establishment, when seedling height is less than that of the competitive vegetation. If the latter can not be removed by some ways (e.g. controlled grazing), then it is safer to use taller oak seedlings of an older age in the reforestation projects.
