Analysis of soil, roots and mycorrhizae in a Norway spruce declining forest

Decline symptoms have been detected in a Norway spruce (Picea abies (L.) Karst.) stand in Vigo di Ton on the Northeastern Italian Alps. Studies were carried out in two close areas which were chosen because of their similar stand age and soil type but differences in crown conditions. The two areas didnʹt show marked differences in the chemical and physical soil parameters investigated but varied in volume and thickness of main horizons. The density of roots was significantly higher in H (healthy) compared to D (damaged) areas considering roots of all diameters. The percentage of mycorrhization was very high and similar in H and D, showing in D a higher frequency of types with less complex ramification and a more marked decrease of diversity of types with depth. However, it is concluded that the symptoms of decline didnʹt have their main origin in the belowground conditions which we investigated, because of the lack of statistically significant differences between the two areas.