University of California

Past forest management promoted root disease in Yosemite Valley


Garey W. Slaughter
David M. Rizzo

Authors Affiliations

G.W. Slaughter is Staff Research Associate, Department of Plant Pathology, UC Davis; D.M. Rizzo is Assistant Professor, Department of Plant Pathology, UC Davis.

Publication Information

Hilgardia 53(3):17-24. DOI:10.3733/ca.v053n03p17. May 1999.

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Root disease is one of the most important vegetation-management considerations in Yosemite Valley. Large trees with root decay have fallen in the valley causing human fatalities and property damage. Many of the problems associated with root disease in Yosemite Valley can be traced back to the area's history of vegetation management. Wildfire suppression and meadow draining were implemented after the arrival of Euroamericans in the mid-19th century. These practices created conditions that encouraged the development of a dense conifer forest within the valley. Tree removals for vista clearance, campground and lodging construction, and bark beetle control projects created thousands of stumps. Many of these stumps have been infected with spores of Heter-obasidion annosum, a fungal pathogen that causes root decay in conifers. The fungus has since spread from initial infection sites into the surrounding forest, creating hundreds of enlarging tree mortality gaps. Park resource managers have established a program of hazardous-tree removal, but efforts to restore natural ecosystem processes must be continuously reconciled with public safety.


Felix LS, Parmeter JR, Uhrenhoidt B., Kuhlman EG. Fomes annosus as a factor in the management of recreational forests. Proceedings of the Fourth International Conference on Fomes annosus. USDA Forest Service, Asheville, North Carolina 1974. 6.

Gibbens RP, Heady HF. The influence of modern man on the vegetation of Yosemite Valley. California Agricultural Experiment Station Manual. 1964. 36:44-

Heady HF, Zinke PJ. Vegetational changes in Yosemite Valley. National Park Service Occasional Paper Number Five 1978. p.25.

Marosy M, Parmeter JR, Otrosina WJ, Scharf RF. The incidence and impact of Heterobasidion annosum on pine and incense cedar in California forests. Proceedings of the symposium on research and management of annosus root disease (Heterobasidion annosum) in western North America. USDA Forest Serv. Gen. Tech. Rpt. PSW-116 1989. 81.

Miller JM, Keen FP. Biology and control of the western pine beetle. USDA Misc. Publication 800 1960. p.381.

National Park Service. Vegetation Management Plan, Yosemite National Park. USDI National Park Service 1997. p.254.

Parmeter JR, MacGregor NJ, Smith RS. An evaluation of Fomes annosus in Yosemite National Park. USDA Forest Service FIDM Report No. 78–2 1978. p.11.

Parmeter JR, Srago M, MacGregor NJ, FW Cobb, Linn RM. Root disease, hazard and forest protection in Yosemite Valley. Proceedings of the First Conference on Scientific Research in the National Parks. Nat. Park Serv. Trans. Procs. Series No. 5 1979. 100.

Slaughter GW, Parmeter JR. Enlargement of mortality centers surrounding pine stumps infected by Heterobasidion annosum in northeastern California. Canad J For Res. 1995. 25:244-52.

Srago M, Parmeter JR, Johnson J, West L. Determining early failure of root-diseased incense-cedars in Yosemite Valley. USDA Forest Service, in cooperation with USDI National Park Service 1978. p.39.

West L., Otrosina WJ, Scharf RF. Management of annosus root disease caused by Heterobasidion annosum in coniferous trees in Yosemite National Park. Proceedings of the symposium on research and management of annosus root disease (Heterobasidion annosum) in western North America. USDA Forest Service Gen. Tech. Rpt. PSW-116 1989. 70.

Slaughter G, Rizzo D. 1999. Past forest management promoted root disease in Yosemite Valley. Hilgardia 53(3):17-24. DOI:10.3733/ca.v053n03p17
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