ARS | Publication request: Microfungi and canopy biology: The distribution of an endemic foliar pathogen and its effects on carbon dioxide flux

Submitted to: Mycological Society of America
Publication Type: Abstract Only
Publication Acceptance Date: April 12, 2005
Publication Date: July 30, 2005
Citation: Kerrigan, J., Stone, J., Manter, D.K., Winton, L. 2005. Microfungi and canopy biology: The distribution of an endemic foliar pathogen and its effects on carbon dioxide flux. Mycological Society of America on CD-ROM.

Technical Abstract: Phaeocryptopus gaeumannii, causal organism of the foliar disease Swiss needle cast of Douglas-fir, is endemic to the Pacific Northwest and widely distributed throughout the natural range of its host. The fungus produces fruiting bodies, pseudothecia, which emerge through and occlude stomata. To contribute to an understanding of how canopy fungi influence canopy processes, we measured the distribution of P. gaeumannii, determined the identity of fungal lineages, and assessed the effects of different colonization levels on gas exchange in the Wind River Experimental Forest in Washington, USA. Incidence of P. gaeumannii in young stands averages approximately 2-5 times greater than in mature and old-growth stands. Population genetic studies have shown that P. gaeumannii is two genetically differentiated, non-recombining sympatric lineages. We found that both lineages are present in the Wind River stands sampled, and that both lineages may occur within the same tree and same needle. One lineage is widespread while the second lineage had only been found in western Oregon prior to this study. A positive linear relationship between the amount of pseudothecia present and a decline in carbon dioxide assimilation rates was recorded. Declines in whole-tree carbon dioxide assimilation rates, ranging from 5-45%, are attributed to colonization by this microscopic fungus.