Biogeochemistry of the Critical Zone

Description

This book highlights recent advances in the discipline of biogeochemistry that have directly resulted from the development of critical zone (CZ) science. The earth's critical zone (CZ) is defined from the weathering front and lowest extent of freely circulating groundwater up through the regolith and to the top of the vegetative canopy. The structure and function of the CZ is shaped through tectonic, lithologic, hydrologic, climatic, and biological processes and is the result of processes occurring at multiple time scales from eons to seconds. The CZ is an open system in which energy and matter are both transported and transformed. Critical zone science provides a novel and unifying framework to consider those coupled interactions that control biogeochemical cycles and fluxes of energy and matter that are critical to sustaining a habitable planet.   Biogeochemical processes are at the heart of energy and matter fluxes through ecosystems and watersheds. They control the quantity and quality of carbon and nutrients available for living organisms, control the retention and export of nutrients affecting water quality and soil fertility, and influence the ability for ecosystems to sequester carbon. As the term implies, biogeochemical cycles, and the rates at which they occur, result from the interaction of biological, chemical, and physical processes. However, finding a unifying framework by which to study these interactions is challenging, and the different components of bio-geo-chemistry are often studied in isolation.   The authors provide both reviews and original research contributions with the requirement that the chapters incorporate a CZ framework to test biogeochemical theory and/or develop new and robust predictive models regarding elemental cycles. The book demonstrates how the CZ framework provides novel insights into biogeochemistry. Series Editor’s Preface Contents 1 An Introduction to Biogeochemistry of the Critical Zone References 2 Hot Spots and Hot Moments in the Critical Zone: Identification of and Incorporation into Reactive Transport Models 2.1 Introduction 2.1.1 Definition of Terms 2.1.2 Scope and Overall Impact 2.2 Capturing Scales and Complexity Using Models 2.2.1 Hot Spots Within the Hyporheic Zone—The Redox Microzone Concept 2.2.2 HSHMs at the Floodplain Scale 2.2.3 HSHMs Along River Corridors 2.3 Current Understanding and the Path Forward 2.3.1 A Conceptual Take on HSHMs Using a Trait-Based Framework 2.3.2 Improvements in Field-Scale Characterization of Hyporheic Zones 2.3.3 Recent Developments in Observation and Modeling of Hot Spots Featuring the Sediment Water Interface 2.4 How Can Models Contribute? 2.4.1 Scale Aware Modeling/Parameterization 2.4.2 A Preemptive Prioritization of HSHMs 2.5 Concluding Remarks References 3 Constraints of Climate and Age on Soil Development in Hawai‘i 3.1 Understanding Critical Zone Functioning Through State Factor Analysis 3.2 Physiographic Setting 3.3 Analytical Approach 3.4 Development of Critical Zone Properties Across the Hawaiian Islands 3.4.1 Weathering Depth and Chemical Denudation 3.4.2 Conditioning Lava Flows for Critical Zone Development 3.5 Biogeochemical Properties of Hawaiian Critical Zone 3.5.1 Weathering and Soil Properties 3.6 Soil Process Domains and Pedogenic Thresholds in Hawai‘i 3.6.1 Process Domains 3.6.2 Transitions Among Process Domains 3.7 Conclusions References 4 Biofilms in the Critical Zone: Distribution and Mediation of Processes 4.1 Introduction 4.2 Documenting Environmental Biofilms Using the Scanning Electron Microscope 4.3 Biofilms in the Critical Zone 4.3.1 Plant Hosted, Biofilms Above Ground: Phyllosphere and Endosphere 4.3.2 Biofilms in the Soil 4.3.3 Biofilms in the Deep Critical Zone 4.4 Biofilm Mediation of Critical Zone Processes 4.4.1 Biofilm Role in OM Stabilization, Biogenic Minerals 4.4.2 Biofilm Role in Mineral Weathering 4.4.3 Biofilm Strategies to Survive Drought 4.5 Summary References 5 Eroded Critical Zone Carbon and Where to Find It: Examples from the IML-CZO 5.1 Introduction 5.1.1 Field Site 5.2 Methods 5.2.1 Estimates of Post-settlement Sediment Accumulation 5.2.2 Organic Carbon Concentrations and C-Isotopic Compositions 5.2.3 Biomarkers 5.3 Results and Discussion 5.3.1 Sediment and OC Inventories 5.3.2 Organic C Sources and Composition 5.4 Conclusions References 6 Advances in Biogeochemical Modeling for Intensively Managed Landscapes 6.1 Introduction 6.2 Long-Term Carbon Dynamics 6.3 Event-Scale Biogeochemical Dynamics: The Impact of Microtopography and Artificial Drainage 6.4 Root Zone Biogeochemistry References 7 Hillslope Position and Land-Use History Influence P Distribution in the Critical Zone 7.1 Introduction 7.1.1 Effect of Ecosystem Development on P Distribution 7.1.2 Effect of Topography on P Distribution 7.1.3 Effect of Land Use on P Distribution 7.1.4 Topography and Land Use in the Calhoun CZO 7.2 Methods 7.2.1 Study Site 7.2.2 Sample Collection 7.2.3 Sample Analyses 7.2.4 Data Analyses 7.3 Results 7.3.1 Soil Analyses 7.3.2 Soil Solution Analyses 7.3.3 Resin Capsule Analyses 7.3.4 Stream Analyses 7.4 Discussion 7.4.1 Hillslope Effects 7.4.2 Effects of Land Use on Vertical Leaching 7.4.3 Soil Solution P 7.4.4 Effects of Land-Use History on P Fractions 7.5 Conclusion References