Effects of drought-induced holm oak dieback on BVOCs emissions in a Mediterranean forest

Climate change is impairing tree physiology and growth, causing an increase in tree dieback in many Mediterranean forests. These desiccation phenomena are leading to changes in land cover and plant community composition. Medi-terranean plants are capable to emit large amount of Biogenic Volatile Organic Compounds (BVOCs), whose emission and biosynthesis is strongly affected by environmental conditions. This study evaluates the seasonal changes in under -story species composition in two forest stands in Southern Tuscany characterized by different levels of Quercus ilex L. crown defoliation (low and high defoliation, LD and HD) and the relationship with BVOCs emissions over three years. We found significant changes in the understory plant community following Q. ilex crown defoliation and mortality, observing an increment in the number of shrubs both in HD and LD stands. The environmental sampling of BVOCs fully reflected the changes in vegetation cover and composition, with a reduction in the amount of monoter-pene emissions due to the increasing rates of defoliation and mortality of Q. ilex trees. Our results suggest that terpene emissions from Mediterranean forests would be modified by an increase of Q. ilex dieback, with important conse-quences for functioning of this forest ecosystem and its atmospheric chemistry.

Automated summary

Climate change is causing tree dieback in Mediterranean forests, leading to changes in land cover and plant community composition. This study examines the relationship between crown defoliation of Quercus ilex trees and understory plant composition, as well as the emissions of Biogenic Volatile Organic Compounds (BVOCs) over three years. The results show that crown defoliation and mortality of Q. ilex trees lead to changes in the understory plant community and a reduction in terpene emissions. This has important implications for the functioning of Mediterranean forest ecosystems and atmospheric chemistry.