Altitudinal variation of trace elements deposition in forest ecosystems along the NW side of Mt. Amiata (central Italy): evidence from topsoil, mosses and epiphytic lichens

Mt. Amiata (1738 m) is a volcanic peak in central Italy, completely covered with native oak, chestnut and beech forests. In this Natura 2000 site of Community Importance overlying a large shallow aquifer, climate change and the long-range transport of nutrients and contaminants might have negative impacts on relict plants populations and spring water chemistry. To evaluate the atmospheric deposition of trace elements in Mt. Amiata forest ecosystems, we analyzed the elemental composition of topsoils, epiphytic lichens (Parmelia species) and epigeic moss (Hypnum cupressiforme) between 120 and 1730 m a.s.l. along the NW side of the mountain, which is scarcely affected by natural and anthropogenic sources of metals. The elemental composition of the topsoil is mainly influenced by the different lithologies of the study area (calcareous up to an elevation of 700 m, volcanic up to the summit) and only Pb concentrations increased significantly with the altitude. The total element concentrations in cryptogams, particularly net of the possible contribution from soil particles, showed an enhanced accumulation of Pb, Cd, Hg and Zn in samples collected at altitudes above 1300 m, where beech forest are frequently shrouded in clouds and fog and receive more snow and rain than the lower chestnut and oak woods. Interestingly, the older and metabolically inactive tissues at the base of moss shoots, which are usually overlooked in biomonitoring surveys, appeared to behave as long-term accumulators of Pb. The possible mechanisms involved in the increased bioaccumulation of Mn in cryptogams inhabiting chestnut woods are discussed.