Climate Change Impacts On Soil Water Dynamics, Plant Growth, and GHG Fluxes in Rangeland.

Climate change can have opposing impacts on key ecosystem processes that control carbon and nitrogen cycling. For example, warming associated with elevated greenhouse gas levels tends to dry soils due to increased potential evapotranspiration but elevated CO₂ can counter this by decreasing stomatal conductance and transpiration.  Water impacts are particularly important in water limited rangelands which account for  approximately 30% of Earth’s land area. We used observations from the Prairie Heating and CO₂ Enrichment (PHACE) experiment in southern Wyoming to test the ability of the DayCent ecosystem model to represent the impacts of warming and elevated atmospheric CO₂ on ecosystem dynamics for semiarid grassland ecosystems. Both the model and measurements showed increased soil water content and plant growth under elevated CO₂, decreased soil water contents with warming, and variable effects of warming on plant growth. The DayCent model was then applied to project the long term consequences of climate change on trace gas (N₂O, NO_x, CH₄) fluxes, plant growth, and soil carbon stocks.