Simona Altieri

Traffic pollution affects tree-ring width and isotopic composition of Pinus pinea

This study presents new evidence that radiocarbon, combined with dendrochronological and stable isotopes analysis in tree rings and needles, can help to better understand the influence of pollution on trees. Pinus pinea individuals, adjacent to main roads in the urban area of Caserta (South Italy) and exposed to large amounts of traffic exhaust since 1980, were sampled and the time-related trend in the growth residuals was estimated. We found a consistent decrease in the ring width starting from 1980, with a slight increase in delta(13)C value, which was considered to be a consequence of environmental stress. No clear pattern was identified in delta(15)N, while an increasing effect of the fossil fuel dilution on the atmospheric bomb-enriched (14)C background was detected in tree rings, possibly as a consequence of the increase in traffic exhausts. Our findings suggested that radiocarbon is a very sensitive tool to investigate small-scale (i.e. traffic exhaust at the level crossing) and large-scale (urban area pollution) induced disturbances.

Tree-ring carbon and oxygen isotopes indicate different water use strategies in three Mediterranean shrubs at Capo Caccia (Sardinia, Italy)

Key messageVariations in stable carbon and oxygen isotope compositions of co-occurring plant species reflect their different water use strategies and indicate the importance of screening species’ WUEito plan climate change adaptation strategies.AbstractThe different abilities of plant species to cope with drought have been associated with structural and ecophysiological constraints. In this paper, we evaluate interspecific differences in intrinsic water use efficiency (WUEi) and the ratio of photosynthesis (A) to stomatal conductance (gs) in three co-occurring Mediterranean shrubs: two broad-leaved evergreen (Pistacia lentiscus and Phillyrea angustifolia) and one needle-like-leaved evergreen (Juniperus phoenicea). We used δ13C in rings to assess inter-annual changes in WUEi while the influence of the stomatal conductance was explored through δ18O. Our results indicate consistent differences in WUEi in the three species, largely determined by leaf traits and differences in stomatal conductance control. Juniperus phoenicea could be the most threatened by the current trend of increasing temperature and summers drought. Phillyrea angustifolia and P. lentiscus seem to be less affected by drought stress because of their tighter stomatal control and high survival rate under field conditions. Our study shows that shrubs with different leaf traits employ different plant ecophysiological strategies under drought stress.