THE DECLINE OF A PINUS-NIGRA ARN. REFORESTATION STAND ON A LIMESTONE SUBSTRATE - THE ROLE OF NUTRITIONAL FACTORS EXAMINED BY MEANS OF FOLIAR DIAGNOSIS

The Austrian black pine reforestation projects on Monte Morello, near the heavily populated metropolitan area of Florence (Italy), have been affected for many years now by a severe decline consisting of widespr ead crown yellowing. To investigate the causes of this decline foliar diagnosis methods were used to monitor the nutritional status of ten t rees, sampling and analysing every year, between 1989 and 1992, the cu rrent year needles (c), needles from the previous year (c+1) and from the year before that (c+2). The parameters examined were both chemical (nitrogen, sulphur, magnesium, potassium, calcium, manganese, iron an d lead) and morphological (needle length, flat projection, dry weight, specific dry weight and water content). The findings show a considera ble calcium accumulation as the needles age, accompanied by an increas e in dry weight and specific dry weight, as well as a marked antagonis m to manganese. The influence of the nearby metropolitan area of Flore nce is suggested by the accumulation of lead. ((C) Inra/Elsevier, Pari s).