Butt rot incidence, yield and growth pattern in a tree species experiment in southwestern Sweden

Abstract

Results from a tree species experiment on a fertile site in southwestern Sweden are presented at a stand age of 40–41 years. The previous generation was a Norway spruce ( Picea abies (L.) Karst.) stand heavily infected by Heterobasidion annosum (Fr.) Bref. The initial aim of the experiment was to evaluate the susceptibility of nine tree species to attacks by root and butt rot. The experiment was designed as a randomised block trial with three replicates. Five thinnings have been carried out in which the incidence of butt rot in removed trees has been recorded. In 1993, European larch ( Larix decidua Mill.), Japanese larch ( Larix kaempferi (Lamb.) Carr.) and Sitka spruce ( Picea sitchensis (Bong.) Carr.) exhibited the greatest incidence of butt rot with infections amounting to 95%, 72% and 69% respectively of removed trees. Grand fir ( Abies grandis Lindl.), Norway spruce and Serbian spruce ( Picea omorika (Pancic) Purkyne) showed moderate levels of attack of 29%, 21% and 16% respectively, while no butt rot was found in Scots pine ( Pinus sylvestris L.). It is possible that Scots pine trees might have been infected in the root system, but that the rot had not extended to the butt. Heterobasidion annosum was the main butt rot causing fungus. All isolates of H. annosum were of the P-group. Grand fir showed the greatest mean and current annual volume increments. Mean annual volume increment was still increasing for all species except for Japanese larch in which a culmination had been reached at the age of 40 years. It is concluded that caution should be taken before European larch, Japanese larch or Sitka spruce are recommended on sites where the previous generation consisted of Norway spruce heavily infected by the P-group of H. annosum.