Leaf morphology and macronutrients in broadleaved trees in central Italy

As part of an intensive monitoring programme (MON.I.TO, Intensive Monitorin g of Forests in Tuscany), a 3-year survey was carried out, which included t hree tree species (beech, Fagus sylvatica L.; Turkey oak, Quercus cerris L. ; holm-oak, Quercus ilex L.) located at six different sites. Leaves were sa mpled annually and analysed for nutrient concentrations (nitrogen, sulphur, phosphorus, magnesium, calcium, potassium and sodium) and morphological pa rameters (leaf area, dry weight, leaf mass per area, leaf thickness and lea f density). Results indicated considerable interannual variation of all the parameters. Differences between sampling sites indicated that, of all para meters measured, leaf mass per area could explain best the differences in f ield performance under conditions of stress. In fact, leaf mass per area wa s greater in the drier sites or when sea salt deposition occurred. Neverthe less, the variation of leaf mass per area over the 3 years did not reflect the differences in rainfall. Higher leaf mass per area was accompanied by l ower concentrations of phosphorus and nitrogen, which could be a dilution e ffect due to an increase of structural carbon compounds in sclerophyllous l eaves, as revealed by the total foliar content of these elements. Leaf mass per area as a measure of sclerophylly reached very high values among mesop hile vegetation. Long-range transport of sea salt from coastal areas to mou ntain areas was mirrored in sodium concentrations of leaves.