Critical Zone Observatory Network for Intensively Managed Landscapes

Critical Zone Observatory Network for Intensively Managed Landscapes Neal Blair and Andy Jacobson, Northwestern University Statement of Work Agricultural intensification, artificial drainage, urbanization, deforestation, and the loss of wetlands in intensively managed landscapes in the US Midwest have dramatically altered the critical zone extending from the top of the plant canopy to the depth of mineral weathering. Better understanding and prediction of critical zone responses to anthropogenic influence is necessary to mitigate the impacts of human activities on both terrestrial and aquatic ecosystems and ultimately sustain food production and ecosystem services. The goal of the project is to establish a critical zone observatory (CZO) to understand and quantify the fluxes, forms, and interactions of water, carbon, nitrogen and sediment in the critical zone of a watershed that is intensively managed and understand how land use practices have altered the watershed's vulnerability and resilience to disturbance. Northwestern University will provide critical geochemical measurements for the hydrology portion of the project with a focus on constraining the paths of water flow and the residence time of water within specific subsurface environments. Samples will be obtained from streams, groundwater wells and tile drains in the Clear Creek (IA) and Upper Sangamon (IL) watersheds. Both base flow and storm events will be sampled for comparative purposes. Sampling will be done in collaboration with University of Illinois and University of Iowa researchers. Neal Blair will be responsible for nitrate δ15N and δ18O, and dissolved inorganic carbon (DIC) and organic C (OC) δ13C measurements. He will also characterize dissolved and particulate organic carbon using a thermochemolytic method employing tetramethylammonium hydroxide (TMAH) and FTIR. Andrew Jacobson will be responsible for major ion, alkalinity, and 87Sr/86Sr measurements.