Leaf shedding, crown condition and element return in two mixed holm oak forests in Tuscany, central Italy

Abstract

Litterfall (leaves, flowers, fruits, twigs) was collected every month in two mixed Mediterranean forests of Quercus ilex (holm oak) in central Italy differing for their ecological features: a mesic site (Colognole, CL) and a xeric one (Cala Violina, CV). The survey period lasted 8 years (1992–2000) at CL and 4 years at CV. Chemical analysis of the litterfall was performed in 1997 and 1998. In these 2 years living leaves were also collected for chemical analysis. The main findings were: (i) the litter production was lower and the leaf percentage in the total litterfall was smaller at CV than at CL; (ii) the phenological behavior differed in the two sites and the leaves had greater longevity at CV, whereas at CL trees renewed their crown almost completely each spring; (iii) the chemical composition of the living leaves reflected the edaphic differences between the two sites; (iv) the chemical composition of the senescent leaves and the litter in the two sites was very different; (v) crown transparency and defoliation followed the same pattern of the leaf shedding; (vi) transparency was greater at CL, where the litter production was higher, because of the different shape of the crowns. The differences between the two study areas have been discussed in the light of the different ecology of the two sites, since leaf lifespan is greater in dry and infertile soils.