Root Diseases and Natural Disease Regimes in Forest of Western U.S.A. : Root and Butt Rots

Uppsala

International Union of Forest Research Organizations, Swedish University of Agricultural Sciences

1994

S. 606-617

9 Lit. Ang.

Bandaufführung

13462

73776

Armillaria and annosum root diseases are common on the Nez Perce National Forest in Idaho (Lockman 1993), U.S.A. The symptoms of root disease activity in conifer stands is observable in color infrared aerial photography. Root disease severity was evaluated in a stratified random sample of stands of all ages using ground survey and aerial photo interpretation. Ninety seven percent of all stands had root disease visible in the photographs. Root disease severity averaged 4.1 (scale 0-9). Subalpine fir, Douglas-fir and grand fir forest types had the highest average severities. Cedar habitat type with a Douglas-fir forest type was the highest overall with an average rating of 6, typified by at least 50 percent reduction in canopy below normal for a site without root disease. Replacement of ponderosa pine and western larch with Douglas-fir has resulted in an increase of root disease severity. Grand fir forest types are also severely affected by root pathogens but probably have a naturally high incidence of disease.