Insights into Event-based Critical-Zone Connectivity in an Intensively Managed Agricultural Landscape in the U.S Midwest

Connectivity among the atmosphere, surface water, groundwater, soil, and sediments at different spatial scales during weather-related events is key to the operation of the critical zone but is poorly delineated. Connectivity, or the lack thereof, produces spatial and temporal variability in runoff, constituent transport, and water storage. Typical research efforts focus on quantifying functional connections between one or two landscape processes, potentially missing important feedbacks or thresholds that may vary with event magnitude, duration, frequency, spatial extent, and antecedent conditions. This is particularly important when events occur in environmental settings in which human modification of landscape form and processes impede or enhance connectivity. This research examines how gases, sediments, and solutes respond to specific events, such as droughts, wet periods, and seasonal variations in weather conditions, in intensively managed landscapes of Illinois and Nebraska. We analyze data collected for the Critical Interface Network (CINET) project, which is part of the NSF-funded Critical-Zone Collaborative Network (CZCN). These data consist of critical-zone observations from an eddy covariance tower, a RiverLab facility taking high-frequency river-chemistry measurements, automated river-suspended sediment samplers, and “management-induced reactive zone” monitoring systems.  We explore how systems respond differently among events and among constituents with modeling and data-driven analyses, and show how natural and anthropogenic factors control connections and disconnections in different parts of the landscape. Through this case study, we illustrate how interfaces between different components of the landscape are important loci for regulating event-scale connectivity across the entire landscape. We also lay out a framework of crucial considerations when quantifying responses of the critical zone to events.