Influence of soil properties on the mortality of silver fir in Tuscany, Italy

With regard to the high mortality of silver fir (Abies alba Mill.) in Italy , pathological and climatic causes are considered crucial, while soil prope rties are usually neglected. Two of the largest Tuscan forests of this spec ies, the one of Vallombrosa and the other of Mount Amiata, are seriously af fected by Heter obasidion annosum, a fungus causing root rot. However, in s pite of the same provenance of firs and intersterile group of the fungus, t he tree death is different at the two sites. In one case, firs quickly died standing, while in the other they were uprooted after a slow course of the illness. A study Nas conducted on the two localities to perceive the role of soil properties in this connection. In the light of our results, pedolog ical conditions are important, negatively affecting the plants either "dire ctly" - limiting deep rooting and preventing the trees to achieve sufficien t anchorage in the ground - and "indirectly" - favouring the sp read and th e virulence of H. annosum.