Playa Wetlands: Ecosystem Functions and Potential Risks in a Changing Climate.

Playas are shallow, recharge wetlands located throughout the High Plains region and entirely dependent on precipitation and runoff for inundation. Playas provide many essential ecosystem functions, including nutrient filtration, groundwater recharge, and wildlife habitat. Regional climate models for the High Plains predict increased temperatures and precipitation intensity in the next thirty years. Changes in playa hydroperiod (frequency, duration and depth of inundation) may affect soil function, which will impact human and wildlife populations throughout the High Plains region. In order to assess potential risks to playas in a changing climate, we are conducting experiments to quantify the effects of changing climatic conditions on playa plant production, soil chemistry and biogeochemical cycling, and ecological tipping point in playa ecosystems. A six-month greenhouse experiment is being conducted to quantify treatment effects (based on predicted climate changes) on seed bank plant production, soil chemical properties, and ion speciation. Soil mesocosm containers are being subjected to four hydroperiod treatments, representing historic and future climate conditions. Local weather station data were used to create the current climatic simulation and CMIP5 – BCCA downscaled atmosphere ocean general circulation models (AOGCMs) for the RCP 4.5 emission scenarios (years 2071-2099) correlated with a geographic location in the playa regions of Nebraska and Texas were used to develop future climatic simulations. Aboveground and belowground plant production, as well as seed biomass will be measured by dry weight at the end of the experiment. Plant species composition is measured monthly using the Simpson’s Diversity Index. Plant physiological response is measured monthly using chlorophyll content and photosynthetic rate of the dominant species. Soil moisture is measured daily. Soil moisture readings are being used to track treatment conditions and deionized water is added as needed to maintain treatment appropriate conditions. Soil temperature and redox potential are measured continuously using a data logger and sensors. Soil solution samples are collected following heavy rainfall events (defined by soil moisture conditions exceeding field capacity moisture content) using suction lysimeters and bulk soil samples are collected biweekly throughout the experiment. Results of this experiment will identify vegetation and soil properties most sensitive to hydroperiod alteration and identify the greatest potential risks to playa soils, allowing scientists to better understand and conserve playa soil functions in a changing climate.