Redox Heterogeneity Entangles Soil and Climate Interactions

Abstract

Interactions between soils and climate impact wider environmental sustainability. Soil heterogeneity intricately regulates these interactions over short spatiotemporal scales and therefore needs to be more finely examined. This paper examines how redox heterogeneity at the level of minerals, microbial cells, organic matter, and the rhizosphere entangles biogeochemical cycles in soil with climate change. Redox heterogeneity is used to develop a conceptual framework that encompasses soil microsites (anaerobic and aerobic) and cryptic biogeochemical cycling, helping to explain poorly understood processes such as methanogenesis in oxygenated soils. This framework is further shown to disentangle global carbon (C) and nitrogen (N) pathways that include CO2, CH4, and N2O. Climate-driven redox perturbations are discussed using wetlands and tropical forests as model systems. Powerful analytical methods are proposed to be combined and used more extensively to study coupled abiotic and biotic reactions that are affected by redox heterogeneity. A core view is that emerging and future research will benefit substantially from developing multifaceted analyses of redox heterogeneity over short spatiotemporal scales in soil. Taking a leap in our understanding of soil and climate interactions and their evolving influence on environmental sustainability then depends on greater collaborative efforts to comprehensively investigate redox heterogeneity spanning the domain of microscopic soil interfaces.

Towards Understanding Factors Affecting Arsenic, Chromium, and Vanadium Mobility in the Subsurface

“…Oxic and anoxic groundwater can be separated by centimeters to tens of meters vertically—capable of mixing across the scale of a well screen—and meters to hundreds of meters along a flow path (although key microscale redox variation may occur at the pore scale [ 37 , 38 ]). Groundwater evolves toward redox interfaces both vertically where groundwater flows predominantly downward (e.g., hilltop areas) and laterally where groundwater predominantly flows toward local stream valleys.…”

Consider the Anoxic Microsite: Acknowledging and Appreciating Spatiotemporal Redox Heterogeneity in Soils and Sediments

“…Years later, microelectrode measurements confirmed localized anoxia at the interior of both saturated and unsaturated aggregates. Evidence of anoxic microsites has been observed in soils across multiple ecosystems, such as tropical and temperate forests, agricultural lands, deserts, and floodplains. − Increasingly, anoxic microsites are recognized as an important but ill-defined control on soil greenhouse gas emissions − and contaminant transport. , Yet, despite their prevalence, long-known presence, and presumed importance, our understanding of anoxic microsites remains incomplete. The soil properties and processes that shape anoxic microsite dynamics have only been partially characterized, and the influence of anoxic microsites on various biogeochemical cycles is still undefined.…”

“…Evidence of anoxic microsites has been observed in soils across multiple ecosystems, such as tropical and temperate forests, agricultural lands, deserts, and floodplains. 37 − 41 Increasingly, anoxic microsites are recognized as an important but ill-defined control on soil greenhouse gas emissions 42 − 44 and contaminant transport. 45 , 46 Yet, despite their prevalence, long-known presence, and presumed importance, our understanding of anoxic microsites remains incomplete.…”

Optical chemical sensors for soil analysis: possibilities and challenges of visualising NH3 concentrations as well as pH and O2 microscale heterogeneity

“…These sites are involved in important soil processes, including both nutrient cycling and gas formation, as they are highly inuenced by soil heterogeneity. [4][5][6][7] Hence, the pedosphere is impacted by a mosaic of microenvironments and distinct chemical conditions on a small scale, which in turn impacts the other spheres on a large scale.…”