Thumbnail Photographs of Ectomycorrhiza Types

Mycorrhizae are long-lived symbioses between fungi and the roots of higher plants. The fungi extend the nutrient-absorbing surface area of the roots; produce extracellular enzymes which increase phosphorous and nitrogen availability; increase host drought tolerance; and protect against pathogens. In return, the fungi receive host photosynthate as their main source of carbon. Ectomycorrhizal fungi (EMF) are essential for host plant nutrient uptake and play important roles in nutrient cycling in many forests. For example, an estimated 50 to 70 percent of the net annual productivity may be translocated to roots and associated mycorrhizal fungi.

Exudates and hyphae of EMF form a major link between above-ground producers and soil food webs, providing carbon for a wide range of bacteria, protozoa, arthropods and microfungi. Mycorrhizal fungi are also important in above?ground food webs. EMF, with few exceptions, produce macroscopic sporocarps (mushrooms and truffles) that are important in the diets of animals, especially small mammals. Some rodents such as the California red-backed vole (Clethrionomys californicus) and northern flying squirrels (Glaucomys sabrinus) rely on these sporocarps for over 90% of their food supply and are primary prey for species such as the Northern Spotted Owl.

These ectomycorrhizae are from soil cores taken at the Siskiyou Intergrated Research Site in southwest Oregon. Photos by D.L. Luoma.

Click on thumbnail to load enLARGEment. Last modified January 16, 2001.

C6unknown fungus

D6Truncocolumella citrina on Pseudotsuga menziesii

E2Lactarius rubrilacteus on Pseudotsuga menziesii

F8Leucogaster rubescens on Pseudotsuga menziesii

I6Hysterangium sp. on Lithocarpus densiflorus

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