Soil Functions in Earth's Critical Zone

Abstract

This chapter summarises the methods, results and conclusions of a 5-year research project (SoilTrEC: soil transformations in European catchments) on experimentation, process modelling and computational simulation of soil functions and soil threats across a network of European, Chinese and USA Critical Zone Observatories (CZOs). The study focussed on the soil functions of biomass production, carbon storage, water storage and transmission, water filtration, transformation of nutrients and maintaining habitat and genetic diversity.The principal results demonstrated that soil functions can be quantified as biophysical flows and transformations of material and energy and simulated with mathematical models of soil processes within the soil profile and at the critical zone interfaces with vegetation and atmosphere, surface waters and the below-ground vadose zone and groundwater. A new dynamic model for soil structure development, together with data sets from the CZOs, demonstrate both seasonal fluctuations in soil structure dynamics related to vegetation dynamics and soil carbon inputs, and long-term trends (decade) trends in soil carbon storage and soil structure development.Cross-site comparison for 20 soil profiles at 7 field sites with variation in soil type, lithology, land cover, land use and climate demonstrated that sites can be classified using model parameter values for soil aggregation processes together with climatic conditions and soil physical properties, along a trajectory of soil structure development from incipient soil formation through productive land use to overly-intensive land use with soil degradation.A new modelling code, the Integrated Critical Zone Model, was applied with parameter sets developed from the CZO site data to simulate the biophysical flows and transformations that quantify multiple soil functions. Process simulations coupled the new model for soil structure dynamics with existing modelling approaches for soil carbon dynamics, nutrient transformations, vegetation dynamics, hydrological flow and transport, and geochemical equilibria and mineral weathering reactions. Successful calibration, testing and application of the model with data sets from horticulture plot manipulation experiments demonstrate the potential to apply modelling and simulation to the scoping and design of new practices and policy options to enhance soil functions and reduce soil threats worldwide.

Critical Zone Services: Expanding Context, Constraints, and Currency beyond Ecosystem Services

“…1). Services include conversion of minerals and nutrients from unavailable lithic forms to biologically available forms, weathering‐induced carbon sequestration, flood attenuation, and attenuation of pollutants (Banwart et al, 2013). Critical zone development occurs over longer time scales than ecosystem succession (Chadwick et al, 1999; Vitousek et al, 2003).…”

“…Energy that does work in developing the structure of the critical zone (as quantified, e.g., by Rasmussen et al, 2011; Kleidon et al, 2012) is effectively stabilizing services into the future as opposed to energy that flows through the system quickly, providing limited services. For example, carbon storage or water storage in the critical zone is a valued service, but carbon in the atmosphere provides limited services and is in most cases considered undesirable (Banwart et al, 2013). Recently, a method was developed for quantifying the energy and mass flowing into the critical zone from effective precipitation and primary production into a simple collapsed metric, enabling an expanded approach for valuing ecosystem services (Fig.…”

“…Therefore, an improved bridge is needed between ecosystem services and the constraints thereon associated with critical zone processes. Because subsurface critical zone processes affect society, an expanded perspective of ecosystem services that encompasses the critical zone— critical zone services (Banwart et al, 2011, 2013; see also NSF Program Solicitation 12‐575; http://www.nsf.gov/pubs/2012/nsf12575/nsf12575.htm, accessed 5 Dec. 2014)—would allow a more comprehensive valuation of services that benefit societal needs.…”

Soil Organic Carbon Across Mexico and the Conterminous United States (1991–2010)

“…Previous studies suggest that the greatest source of discrepancy across regional to global carbon cycling estimates is associated with the SOC pool (Crowther et al, 2016;Jones et al, 2005;Jones & Falloon, 2009;Murray-Tortarolo et al, 2016;Tifafi et al, 2017). Arguably, current scientific challenges associated with the discrepancy of the soil carbon pool are to quantify (1) the size and distribution of local to regional SOC stocks at scales relevant to inform land management decisions (FAO, 2017, Banwart et al, 2017; (2) the amount of carbon losses from soils due to heterotrophic respiration (Bond-Lamberty et al, 2018), the amount of carbon removed from erosion (Naipal et al, 2018) or aquatic export (Tank et al, 2018), or changes in land use and land cover (Sanderman et al, 2017); and (3) the carbon emissions from impacts of past and future climate conditions (Crowther et al, 2016;Delgado-Baquerizo et al, 2017;Walsh et al, 2017). Solving these scientific challenges around carbon cycling requires a good understanding of different uncertainty sources around SOC datasets and SOC modeling efforts.…”

Qualitative and quantitative soil organic matter estimation for sustainable soil management

“…biological habitat and gene pool, source of raw materials, climate regulations, physical and cultural heritage, platform for man-made structure (Blum 2005;Dominati et al 2010;Banwart et al 2017). Soil is extremely important as a filter removing pollution from water and helping to regulate the flow of water through the landscape (Rawls et al 2003;Keesstra et al 2012).…”