ARE DESERT EPHEMERAL BODIES OF WATER SOURCES OR SINKS OF CARBON?

Climate change models for the Chihuahuan Desert suggest increased intensity and variability of precipitation events. Small water bodies, used historically as watering tanks for cattle, fill with precipitation and provide ecologically interesting playa-wetland. These provide a fresh water source for neighboring flora and fauna. Soil microbial activity is extremely important in soil ecological functionality, as they regulate various nutrient cycling and decompose organic matter. The production of CO₂ and CH₄ through soil respiration (SR) can be dependent on hydroperiod length; where drier ponds may have increased CO₂ production over CH₄ and ponds with prominent hydroperiod may release more CH₄ over CO₂. Most microbial metabolic activity is dependent on water availability; therefore, their CO₂ and CH₄ contributions are reliant on precipitation patterns. Biolog Ecoplates are used to assess functional diversity from eight individual playa-wetlands at the Indio Mountains Research Station, located within northern Chihuahuan Desert landscapes. Soil monolith cores from the top 20 cm will be taken from the ponds during dry season and placed in small closed incubated chambers, forming mesocosms, which will be exposed to simulated temperatures and drying and wetting events of varying frequencies. Emission of CO₂ and CH₄ will be measured hourly until soils return to dry conditions using an INNOVA gas analyzer.  Preliminary data suggests differences in soil microbial functional diversity are dependent on soil moisture availability. Said diversity can imply different carbon emissions with varying moisture gradients. Continued research will provide insight on if these ponds are sinks or sources of carbon into the atmosphere.