Healthy soils support the production of food, store rainfall, transmit and filter groundwater, and provide habitat for plants, animals, and microbes. Much of the volume of these soils is comprised of aggregates that represent the binding of particles (e.g., clay) and organic matter (generated by plants and microbes) into larger units. How these larger aggregate units are arranged controls the shapes of pores between aggregates, and thus the characteristics of the pore network. As a result, aggregate arrangement governs how water flows through soil. Interestingly, aggregates have a life-cycle: they form, persist for largely unknown time periods, and then degrade. Several recent studies suggest that the speed at which aggregates move through this life-cycle is controlled by changes in rainfall, temperature, and land-use patterns. This research aims to make explicit linkages between environmental drivers and aggregate life-cycles across various scales: from very small individual aggregates, to their arrangements and effects on water flow through a soil profile, and, finally, how they influence water flow at hillslope, regional, and continental scales. At these broader scales, this study will uncover the role that these aggregate life-cycles and arrangements have on influencing soil moisture, vegetation and climate. Findings from this work will reveal how soils respond to changing climate and how those responses can in turn influence climate, facilitate model development for forecasting the impacts of climate change on water resources, food production and ecosystems, and promote the development of strategies to adapt to future environmental realities.
The goal of this research is to mechanistically link soil aggregate life-cycles and arrangements to water flow, carbon cycling, and biogeochemical fluxes from soil particles to continental scales. Aggregate soil organic carbon (SOC) is a key structural component that gives rise to the soil pore and hydraulic properties observed at broader soil horizon and pedon scales. Thus, by examining both biotic and abiotic mechanisms governing rates of formation and collapse of soil aggregates, investigators can quantify and project the structural response of the soil fabric to changing climate and land use—features largely overlooked in current modeling frameworks. To accomplish this goal, our multi-disciplinary team will leverage soil samples and data from existing environmental observatories (e.g., United States Department of Agriculture, NSF-funded long-term research sites) and National Ecological Observatory Network sites, as well as ancillary data (e.g., Natural Resources Conservation Service Soil Climate Analysis Network and remotely sensed products), that represent gradients of climate, land use, and soil texture to: 1) investigate biotic and abiotic drivers of soil aggregate formation and collapse, arrangement, and pore geometry through manipulative experiments that quantify the influence of binding agent abundance, mineral surface area, and overburden pressure, which varies with soil depth, on these trajectories; 2) relate gross rates of aggregate formation and collapse to rates of microbial activity and SOC mineralization; 3) quantify how and to what degree aggregate arrangements influence porosity and, thus, water and C fluxes with depth; 4) develop new tools that leverage remotely-sensed soil moisture and vegetation properties at the soil surface to predict depth distributions of soil aggregate and related properties; 5) integrate a mechanistic understanding of empirically quantified soil processes from the individual aggregate to the pedon scale into hillslope- to watershed-scale models to project soil biogeochemical responses to changes in soil pore development; and, 6) model the continental-scale effects of changing aggregate life-cycles and arrangements on the biogeochemistry of soil systems and resulting feedbacks to climate. Advances from this research will improve understanding of soil capacity to perform ecosystem services now and in the future, elucidating physical, chemical, and biogeochemical processes affecting fluxes, transformation, and storage of water and C in ecosystems.
This award was made through the Signals in the Soil (SitS)' solicitation, a collaborative partnership between the National Science Foundation and the United States Department of Agriculture National Institute of Food and Agriculture (USDA NIFA).
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
|Effective start/end date||1/15/21 → 12/31/24|
- National Science Foundation: $233,042.00