Enlargement of canopy gaps associated with a fungal pathogen in Yosemite Valley, California

• Published in: Canadian journal of forest research Vol. 30; no. 10; pp. 1501 - 1510
• Main Authors: Rizzo, D.M, Slaughter, G.W, Parmeter, J.R. Jr
• Format: Journal Article
• Language: English
• Published: Ottawa, Canada NRC Research Press 01.10.2000; National Research Council of Canada; Canadian Science Publishing NRC Research Press
• Subjects: Bark; basal area; Biological and medical sciences; Canopies; canopy gaps; Coniferous forests; Coniferous trees; Decay; diameter; Diseases & pests; Forests; Fundamental and applied biological sciences. Psychology; fungal diseases of plants; Fungal plant pathogens; Heterobasidion annosum; Karst; Mixed forests; monitoring; Mortality; Pathogens; Pathology, epidemiology, host-fungus relationships. Damages, economic importance; Phytopathology. Animal pests. Plant and forest protection; Pine trees; root rot; Roots; Roots (Botany); spatial distribution; stand density; stumps; California; United States; North America; America; Stand density; Forest stand; Plant pathogen; Heterobasidion annosum; Root; Mortality; Basidiomycetes; Vegetation dynamics; Epidemiology; Canopy gap; Time variation; Fungi; Infection; Basal area; Pinus ponderosa; Softwood forest tree; Wood destroying fungi; Gymnospermae; Coniferales; Spermatophyta; Vegetation structure; Thallophyta
• ISSN: 0045-5067; 1208-6037
• DOI: 10.1139/x00-073

The enlargement of 21 canopy gaps associated with the root pathogen Heterobasidion annosum (Fr.:Fr.) Bref. = Fomes annosus (Fr.) Karst.) in the mixed-conifer forest of Yosemite Valley was monitored between 1971 and 1998. Mean expanded gap area was 232 m 2 (range 38-802 m 2 ) in 1971 and 1455 m 2 (range 150-4216 m 2 ) in 1998. The pathogen is primarily spread among trees via root contacts; therefore, the spread and impact of H. annosum from the stump(s) where infection originated (gap makers) were characterized by describing the area of potential root contact as a variable-area plot. The potential root contact zone delineated the area that would be encompassed by mortality if all trees potentially in contact with the original gap makers had died. Of the 21 plots, the actual area of tree mortality exceeded the potential root contact zone in only two gaps. Enlargement rates around gap perimeters were uneven, ranging from 0 to 1.33 m/year. Incense-cedars (Calocedrus decurrens (Torr.) Florin) tended to die more slowly than ponderosa pines (Pinus ponderosa Dougl.), often 10-30 years after adjacent pines had died. Gap enlargement was not dependent on host density, basal area, or gap-maker diameter, and tended to stabilize over time, probably because of fungal competition in root wood and lack of sufficient suitable host material along gap margins.