Dissertation Research: Tradeoff of Carbon and Water with Agricultural Conversion of Grasslands

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Climate change and water shortages are two serious global environmental issues that are projected to worsen in the near future. However, humans may be able to mitigate these problems by promoting certain ecosystem processes, a concept known as ecosystem services. Two examples are storing carbon from atmospheric carbon dioxide, one of the main contributors to climate change, into plants and soil, and recharging rainfall to groundwater. Vegetation controls these services because it stores carbon, but uses water to do so. Human activities, such as conversion of natural vegetation to agriculture, hence can alter the effectiveness of these services. Recognizing the tradeoff between vegetation's control over carbon and water, this research will address how agriculture changes grassland carbon and water storages. The U.S. Great Plains are particularly important because they store large amounts of carbon, occur in drier climates, and contain more than half of U.S. agriculture. Water inputs from irrigation and rain should enhance plant production, which form the basis for carbon storage, but plant production may decrease water availability and deep water storage. To establish a general relationship between water inputs and the services, the study is conducted at six sites along a rainfall gradient in the southern Great Plains in which irrigated and rain-fed agricultures, and grasslands are compared. Deep soil is sampled for carbon and tracer ions to estimate carbon and recharge to groundwater. The broader impacts include estimation of environmental benefits and costs of agricultural conversion in consideration of multiple ecosystem services. Undergraduate and Masters students will be mentored, and results will be shared with landowners, experimental agricultural stations and local Water Development Boards.