Sanpisa Sritrairat - Biogeochemistry Lab

Rensselaer Polytechnic Institute, Troy, NY




Effect of Different Drought Frequencies on Soil Microbial Metabolic Pathways at SERC's Beaver Meadow


In freshwater system, the three major anaerobic metabolic pathways are Fe(III) reduction, sulfate reduction, and methane production, with the methanogenesis yielding the least energy. Wetlands are a major source of methane, a strong greenhouse gas, as a result of this anaerobic methane production in the saturated soil. Thus, understanding the methanogenesis and related anaerobic metabolism pathways in the wetland is a key factor in understanding the trend of future climate. At the same time, the effects of climate change on methane production will be important. The future climate will change the amount of precipitation, which can alter the water table in wetlands. While many researchers found that the higher water table increased methane production, the effect of drought frequency on the Fe(III) reduction and iron cylcing is not well known. Using a new beaver pond, which is a subject to frequent drought, as a study site, poorly crystalline iron content at various elevations and reduction rate of the three pathways in the pond were quantified. We expected to see lower methane production at higher elevation, where drought should occur at the highest frequency. Nevertheless, we found that the amount of oxidized poorly crystalline iron. Nevertheless, we did not found an accumulation of Fe(III) at higher elevation. From our result, we suspected that there might be chemical reduction of iron and sulfate, forming iron sulfides and creating sulfate cycle during drought year. This is related with the depletion of Fe(III). Thus, the methane production might not be lower in higher drought frequency

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