Elements dynamics, from leaf to stable leaf litter residue and soil, for two functional types of tree planted on volcanic deposits.

Purposes: The aim of this paper was to characterize elements dynamics, including resorption before leaf shedding and accumulation/release during decomposition, of two functionally different tree species, the N-fixing, broadleaf, deciduous black locust (Robinia pseudoacacia L.), and the Mediterranean black pine (Pinus nigra Arn.), planted on recent unconsolidated volcanic deposits. Methods: In two paired, 40 years old stands, we investigated the stoichiometry of thirteen elements in green leaves, newly shed leaf litter, stable litter residue and soil. Results: Black locust leaves were richer in N, P, K, Mg and Mn; black pine needles were richer in Na, Fe, Zn, Cr, and Pb. Resorption efficiency was Pb > Zn > Fe ~ N ~ Mn ~ Mg > Cd ~ K > P in black locust, and Pb ~ Cu > Zn ~ Na > Mn > K ~ Cr in black pine. Compared to black pine, black locust newly shed litter was richer in K, Na, Mn, Cu, and Ni. During decomposition, black locust leaf litter released N, K, Mg, Na, Mn, Zn, Cu and Cd, and accumulated Fe, Ni, Cr and Pb, whilst black pine needles released N, Zn and Cd, and accumulated all the other elements. Compared to black locust black pine had a stable needle litter residue richer in all elements but N, whilst the mineral soil was poorer in all elements but Pb. Conclusions: The two functionally different tree species have distinct element dynamics from leaf to far decomposed litter. Element sequestration in the stable residue of black pine litter, likely prevents their release in the mineral soil that is thus poorer in nutrients and minor elements compared to the soil of black locust. [ABSTRACT FROM AUTHOR]