Butt rot incidence, causal fungi, and related yield loss in Picea abies stands of Latvia

Root and butt rot is the most destructive disease of conifers in the Northern Hemisphere, but little is known about the dynamics of yield loss in stands of different ages, site types, and species composition. This study aimed to estimate butt rot incidence, causal fungi, and related wood yield loss in Picea abies (L.) H. Karst. stands in Latvia. A total of 24 745 stumps were examined on 318 forest sites, and 21.8% of them contained rot. There was a positive correlation between stand age and butt rot frequency. Proportion of other tree species in a stand had no influence on incidence of the rot, but significant differences were observed among different forest site types. The length of decay columns in 114 stems analysed was 6.6 +/- 2.6 m on average. Based on the observed butt rot frequencies in Latvian P. abies stands of different age classes, volumes of decay-degraded wood in a fully stocked stand would comprise about 19.7 m(3).ha(-1) at the age of 40 years, 57.4 m(3).ha(-1) at 60 years, 54.9 m(3).ha(-1) at 80 years, 63.1 m(3).ha(-1) at 100 years, and 91.8 m(3)-ha(-1) at 120 years, corresponding to 6%-16% of a total standing volume.