Investigation of the effects of Mount St. Helens tephra on soil gas composition and subsequent effects on root and mycorrhizal growth of Abies amabilis

It was hypothesized that tephra from the May 1980 eruption of Mount St. Helens would form an impervious layer, limiting gas exchange (oxygen and carbon dioxide) in the soil. Resulting limited oxygen and excessive carbon dioxide were predicted to affect root and mycorrhizal growth of Pacific silver fir (Abies amabilis) causing higher than normal foliage loss.


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