Linking Soil Structure, Hydraulic Properties, and Organic Carbon Dynamics: A Holistic Framework to Study the Impact of Climate Change and Land Management

Abstract

Climate change and unsustainable land management practices have resulted in extensive soil degradation, including alteration of soil structure (i.e., aggregate and pore size distributions), loss of soil organic carbon, and reduction of water and nutrient holding capacities. Although soil structure, hydrologic processes, and biogeochemical fluxes are tightly linked, their interaction is often unaccounted for in current ecohydrological, hydrological and terrestrial biosphere models. For more holistic predictions of soil hydrological and biogeochemical cycles, models need to incorporate soil structure and macroporosity dynamics, whether in a natural or agricultural ecosystem. Here, we present a theoretical framework that couples soil hydrologic processes and soil microbial activity to soil organic carbon dynamics through the dynamics of soil structure. In particular, we link the Millennial model for soil carbon dynamics, which explicitly models the formation and breakdown of soil aggregates, to a recent parameterization of the soil water retention and hydraulic conductivity curves and to solute and O2 diffusivities to soil microsites based on soil macroporosity. To illustrate the significance of incorporating the dynamics of soil structure, we apply the framework to a case study in which soil and vegetation recover over time from agricultural practices. The new framework enables more holistic predictions of the effects of climate change and land management practices on coupled soil hydrological and biogeochemical cycles.

Response of maize yield to changes in soil organic matter in a Swedish long‐term experiment

“…Already small increases in SOC at a global scale have been estimated to enhance farmers' output during drought years while reducing global temperature warming (Iizumi & Wagai, 2019). The mechanisms through which SOC affects crop biomass production are numerous (Jha et al, 2023;Johnston et al, 2009;Meurer, Barron, et al, 2020;Rubio et al, 2021;Schjønning et al, 2012). They include biogeochemical processes such as increased turnover and supply of nutrients to plants from the mineralization of soil organic matter, and enhanced retention of nutrients through increased cation exchange capacity, as well as physical processes such as better water infiltration, soil structure and structural stability due to stronger aggregation leading to less soil erosion, alleviation of compaction, facilitation of root growth, increased water storage and diffusivity of gases.…”

Integrated Land-Use Systems Contribute to Restoring Water Cycles in the Brazilian Cerrado Biome

“…As the most important species of any pasture component, Brachiaria brizantha, mainly roots in the upper 30 cm of the soil [15]; the dynamic of moisture in the topsoil largely affects the productivity of the pasture and, thus, in addition to seasonal variability, dynamics of vertical-spatial variability of soil moisture within seasons needs to be taken into account when evaluating the effects of land-use change on water availability and -productivity. The soil moisture dynamics depend to a large extent on the concentration of soil organic matter in any soil layer, which, in turn, has been shown to be strongly affected by land-use change [16].…”