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

气候变化和水资源短缺是两个严重的全球环境问题，预计在不久的将来会恶化。然而，人类也许能够通过促进某些生态系统过程来缓解这些问题，这一概念被称为生态系统服务。两个例子是将大气中的二氧化碳（气候变化的主要原因之一）中的碳储存到植物和土壤中，以及将降雨补充到地下水中。植被控制着这些功能，因为它储存碳，但需要水来储存碳。因此，人类活动，例如将自然植被转化为农业，可以改变这些服务的效力。认识到植被对碳和水的控制之间的权衡，本研究将解决农业如何改变草地碳和水的储存。美国大平原尤其重要，因为它们储存了大量的碳，气候干燥，占美国农业的一半以上。灌溉水和雨水的输入应该提高植物产量，这是碳储存的基础，但植物生产可能会降低水的有效性和深层水的储存。为了建立水投入和服务之间的一般关系，研究在大平原南部沿降雨梯度的六个地点进行，比较了灌溉农业和雨养农业以及草地。对深层土壤进行碳和示踪离子取样，以估计碳和地下水的补给。更广泛的影响包括在考虑多种生态系统服务的情况下对农业转化的环境效益和成本进行估计。本科生和硕士生将接受指导，研究结果将与土地所有者、农业实验站和当地水资源开发委员会分享。

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.