Human-induced nitrogen input that has doubled biologically-available nitrogen on Earth
Organic carbon derived from sedimentary rocks that is often poorly quantified and influences soil organic carbon composition, age, and stability
Spatial variability in biogeochemical processes and solute sources within watersheds, particularly between shallow soil zones and deeper groundwater zones
Areas of disproportionately high biogeochemical activity or export relative to surrounding landscape
Geographic patterns in biodiversity and chemical diversity across latitudinal and environmental gradients
Spatial variations in oxidation-reduction conditions within floodplain environments that can form within microsites, along textural transitions, or along the capillary fringe