VEGETATION STRESS IN RELATION TO ELEVATED DIFFUSE CO2 AREAS AT MAMMOTH MOUNTAIN, CA

Elevated diffuse soil CO₂ flux related to magmatic degassing processes has stressed vegetation in several areas at Mammoth Mountain in the Eastern Sierra region of California. At Horseshoe Lake, sustained elevated CO₂ release has produced large areas of dead trees which were first observed in 1990. In this study we assessed the relationship of vegetation health and elevated CO₂ by comparing the chlorophyll index (an indicator of chlorophyll concentration) in living pine trees in relation to CO₂ flux in the Horseshoe Lake tree kill area. Based on measured soil values, diffuse CO₂ flux continues to be elevated, even in areas where pine trees are still living. Trees on the edge of the tree kill area appeared healthy; however, our analysis has shown that the chlorophyll index for all of the trees was much lower compared to similar trees outside of the tree kill area. Past aerial photos of Horseshoe Lake and chlorophyll index readings were then used to specifically investigate how vegetation in the tree kill area has changed over the past 20 years. Overall, the Horseshoe Lake tree kill area provides a natural laboratory to observe how vegetation might respond to elevated CO₂ levels.