USGS - science for a changing world

Elevated CO2 in Forest and Soil Ecosystems (ECO2FASE)

Scientists working in an elevated CO2 landscape

Project Personnel:

Mark Waldrop, Jack McFarland, Margaret Mangan, Bill Evans, Monica Haw, Sabrina Sevilgen, Rob Klinger, Laurel Triatik, Carli Morgan, Lisamarie Windham-Meyers


John King (Lone Pine Research)


USGS Volcano Science Center


High concentrations of volcanic cold CO2 emanating from Mammoth Mountain by the Long Valley Caldera has resulted in several large zones of tree kill over the past two decades. The absence of plants among affected areas has negatively impacted microbial populations, resulting in decreased biomass and/or shift to unique assemblages better adapted to chronic energy stress. However, separating the direct impact of elevated CO2 from the effect of excluding vegetation (and associated C inputs) on soil microbial community structure is complicated. At the Horseshoe Lake tree kill, there is evidence that the effects of elevated CO2 have decreased enough in some areas to allow recolonization of plant-free zones by lodgepole pine. This study capitalizes on the resurgence of plant growth to examine how microbial communities restructure in response to the CO2 disturbance and how resilient they are to returning to pre-starvation levels with the reintroduction of plants. Our sampling sites span a gradient of CO2 ranging from aerobic, to microaerobic, to anaerobic zones completely devoid of plant life. Investigations along this gradient include measures of soil function (enzyme activities, respiration, decomposition) as well as analyses of the composition of broad soil functional groups (fungi, bacteria, and archaea), and specific microorganisms, (CO2-reductive acetogenic bacteria and methanogens), physiologically suited to microaerobic and anaerobic environments. In addition, we are conducting greenhouse trials to determine the influence of mycorrhizae on seedling survivorship and growth for possible future outplanting experiments in affected areas. Information gained from this study should enhance our understanding of the impact of large-scale disturbances on plant-microbial interactions and belowground processes in forested ecosystems, and prove insightful to industries concerned with the effects of accidental release of CO2 from geologic reservoirs.


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