Foliar nutrient dynamics and nutrient-use efficiency in Castanea sativa coppice stands of southern Europe

Chemical and biological aspects of above-ground leaf biomass and nutrient content, redistribution of leaf litter and nutrient return to the soil, seasonal foliar dynamics and nutrient-use efficiency were studied in four Castanea sativa Mill. forests of varying ages near Salamanca (Spain), Montpellier (France) and Catania (Italy). From 49 felled, measured and weighed trees, leaf biomass was determined for each tree relative to their diameter at breast height (d.b.h,). It was possible to establish a single regression equation: Biomass = a(d.b.h.)(b). Young stands had much lower leaf biomass values: (1600 kg ha(-1) and 1500 kg ha(-1)) than the two older stands, (3900 kg ha(-1) and 4100 kg ha(-1) respectively). The amounts of the nutrients immobilized in leaf biomass followed the order: N > K > Ca > Mg > P. The amounts of immobilized N, P, K and Mg were less in young stands than old stands; whereas the amounts of Ca were greater in the young stands. N and P translocation to perennial parts followed the same relationship as nutrient immobilization in above-ground leaf biomass, the K translocation differed in the French stand, whereas for Ca, the pattern differed for the two Italian stands. Magnesium does not follow any pattern. The Spanish plot reabsorbed greater amounts of the nutrients considered, except for P, where the greatest amount occurred in an Italian stand. The French site resorbed similar proportions of N as the Italian stands and considerably lower proportions of Mg and K than the other three stands. The two Italian stands resorbed the same proportions of K and Mg, Fossa la Nave greater proportions of Ca, and Piano Porcheria of P.