The effect of layered lithology on soil formation and landscape evolution A case study in the Flint Hills, Kansas, USA Marte Stoorvogel March, 2019 The effect of layered lithology on soil formation and landscape evolution A case study in the Flint Hills, Kansas, USA M.M. (Marte) Stoorvogel 951113808060 Master thesis Earth and Environment: Soil Geography and Earth Surface Dynamics March, 2019 Wageningen, The Netherlands Soil Geography and Landscape group Wageningen UR Supervisors: W.M. (Marijn) van der Meij MSc Soil Geography and Landscape group Wageningen UR, Netherlands Dr. A.J.A.M (Arnaud) Temme Department of Geography Kansas State University, USA ii Abstract Soil-landscape relations originate from interactions between pedogenic and geomorphic processes. These relations can especially be strong in systems with a layered bedrock lithology as a result of the strong influence of parent material on soil formation. However, previous research has not yet focused on feedbacks between soil and landscape evolution in layered bedrock systems. Therefore, the objective of this research was to get a better understanding of the influence of lithology on soil formation and landscape evolution across hillslopes on layered bedrock. This study was conducted at the Konza Prairie ecological research station in Kansas, USA, where layers of limestone and shale alternate. A field survey, laboratory analysis and model study were performed to reach the objective. Results show that soil properties vary strongly across hillslopes on layered bedrock and that differences in elevation, slope steepness, profile curvature and parent material affect these properties. Especially soil depth, surface stoniness and vegetation coverage follow a clear pattern across the hillslopes, with thin soils, high surface stoniness and low vegetation coverage at convex positions and steep slopes. The most important processes occurring at Konza Prairie appear to be creep, aeolian deposition, bedrock weathering, physical and chemical weathering, clay translocation, bioturbation and organic matter dynamics. Model results of most soil properties show patterns similar to the ones that were found in the field. The evolution of soil properties is strongly dependent on landscape position and an equilibrium situation of the system is not yet reached at the end of the simulation. Given the model performance, the model outcomes gave us insight in the effect of pedogenic and geomorphic processes on layered hillslopes and how these interact. In conclusion, lithology of layered landscapes strongly affects pedogenic and geomorphic processes and the corresponding soil and landscape evolution. iii Acknowledgements First, I would like to thank Marijn van der Meij and Arnaud Temme for their supervision and all their help, advice and useful comments. Moreover, I thank Michael Stumpff for all the days he joined to Konza Prairie for the field work and that he was able to drive us there. Advice and tips given by the Geomorphology group at Kansas State University, including Colleen Gura, Abigail Langston, Abbey Marcotte, Marijn van der Meij, Michael Stumpff and Arnaud Temme, have been a great help during my thesis process. Finally, I would like to thank Jennifer Roozeboom for her help to come up with the laboratory methods and her help during the laboratory work itself. Moreover, I am grateful that I was able to make use of the Paleoenvironmental Lab at Kansas State University and all its equipment. iv Table of Contents 1. Introduction .................................................................................................................................... 1 2. Study area ....................................................................................................................................... 3 2.1 Introduction ............................................................................................................................ 3 2.2 Climate .................................................................................................................................... 3 2.3 Geomorphology ...................................................................................................................... 3 2.4 Watershed K1A ....................................................................................................................... 5 3. Methods .......................................................................................................................................... 6 3.1 Field research .......................................................................................................................... 6 3.1.1 Field survey ..................................................................................................................... 6 3.1.2 Ground-penetrating radar .............................................................................................. 8 3.1.3 Laboratory analysis ......................................................................................................... 9 3.1.4 Data analyses and conceptual figures........................................................................... 10 3.2 LORICA modelling .................................................................................................................. 10 3.2.1 Model structure and processes .................................................................................... 11 3.2.2 Model input and calibration ......................................................................................... 12 3.2.3 Model output and comparison with the field results ................................................... 13 4. Results ........................................................................................................................................... 15 4.1 Field results ........................................................................................................................... 15 4.1.1 Lithology ........................................................................................................................ 15 4.1.2 Soil horizons and classifications .................................................................................... 18 4.1.3 Soil horizon properties .................................................................................................. 20 4.1.4 Study site properties and soil-landscape relations ....................................................... 22 4.1.5 Simplified overview of soil-landscape patterns ............................................................ 28 4.1.6 Conceptual model of soil-landscape feedbacks ............................................................ 29 4.2 Model results ........................................................................................................................ 31 4.2.1 Patterns of soil properties............................................................................................. 31 4.2.2 Statistics of soil properties ............................................................................................ 33 4.2.3 Evolution of soil and landscape properties ................................................................... 35 5. Discussion ...................................................................................................................................... 38 5.1 The spatial distribution of soil properties and feedbacks between geomorphic and pedogenic processes ......................................................................................................................... 38 5.2 The performance of LORICA to simulate soil and landscape properties and temporal soil- landscape dynamics .......................................................................................................................... 43 6. Conclusions ................................................................................................................................... 46 7. References .................................................................................................................................... 47 v Appendix A: Field form ......................................................................................................................... 52 Appendix B: GPR (PulseEkko PRO) settings .......................................................................................... 53 Appendix C: Measurement programme settings of the Malvern Mastersizer 3000 ............................ 54 Appendix D: Adapted bedrock weathering script in LORICA ................................................................ 55 Appendix E: Cross-correlation matrix between soil and landscape properties .................................... 57 Appendix F: Spatial distribution of soil properties at the surface and in the top soil layer ................. 58 vi List of figures Figure 1 Location of Konza Prairie and the Flint Hills in the USA (A) and in Kansas (B) (data from Konza Prairie Long Term Ecological Research Program, 2010; United States Census Bureau Geography Division, 2018; United States Environmental Protection Agency, 2016) ........................ 3 Figure 2 Digital Elevation Model of Konza Prairie (A) and the studied hillslope in watershed K1A (B). Slope steepness at Konza Prairie (C) and the studied hillslope in watershed K1A (D). ..................... 4 Figure 3 Konza Prairie cross-section showing bedrock units and associated benches and slopes (Smith, 1991) .....................................................................................................................................