דעיכת הצומח המעוצה בחבל הים תיכוני בישראל בתגובה לתקופת יובש ממושכת: [מתוך המדור: חזית המחקר]

The climate in the Eastern Mediterranean is becoming increasingly dry due to rising temperatures, shortening of the rainy season, and, a prediction of further decreases in precipitation in the coming decades. Our study examined the impact of climatic changes on the cover and composition of woody perennial vegetation, the dominant component of the Mediterranean vegetation. We assessed changes in woody vegetation cover by comparing two field surveys conducted ten years apart at 71 natural sites across the Mediterranean region of Israel, from the mesic Upper Galilee to the dry Judean Foothills. We characterized the decade between the two surveys as a dry period. The average precipitation during the study period was lower compared to previous decades, particularly in the drier regions. We found a drying trend, which included a reduction in water availability and shortening of the rainy season, and was more severe in relatively dry areas compared to mesic areas. We observed that total woody cover decreased in most of the sites; in 51% of the survey sites, there was a significant reduction of more than 5% in cover, while woody cover increased in only 17% of the sites. We found that the decrease in cover was more severe in drier areas and diminished with increasing precipitation. Additionally, we found that species richness contributed to the stability of cover. Among the 51 plant species found in the survey, we identified seven dominant tree, shrub, and sub-shrub species. Of these, only Quercus coccifera, increased in cover. Phillyrea latifolia and Rhamnus lycioides had relatively stable cover, while the cover of four shrub species, Pistacia lentiscus, Calicotome villosa, Sarcopoterium spinosum and Cistus spp decreased significantly. We identified changes in perennial woody vegetation, which we attributed to the impact of climatic changes. Accordingly, we expect further degradation with continued drying. Conversely, species richness stabilized woody vegetation cover and contribute to the stability of Mediterranean vegetation during dry periods.