Mechanisms of soil organic matter stabilization across a phosphorus and land use gradient in carbonate lithologies.
EMSL Project ID
51893
Abstract
The belowground cycles of carbon (C), nitrogen (N), and phosphorus (P) are controlled by complex local soil forming processes, but the relationships between these cycles remain poorly defined. The belowground C cycle is strongly controlled by soil organic matter (SOM) dynamics, which is balanced by SOM stabilization on soil mineral surfaces and plant and microbial demand for biocritical nutrients. Destabilization of SOM for N is a key link between the belowground C and N cycles, but similar links between the belowground C and P cycles remain undefined, especially with regards to the role P in SOM stabilization. Human activities, such as fertilizer application and land use change, are rapidly altering belowground biogeochemical cycles, but the magnitude of these changes are unknown. Our overall goal is to determine the specific role of P in SOM stabilization and how human activities alter the relationship between the belowground C and P cycles in unmanaged and managed ecosystems. To accomplish this goal, the proposed work will sample soil profiles in two physiographic regions of Kentucky along a gradient of rock-derived P concentrations and land-use type. The study regions are underlain with similar carbonate lithologies that vary strongly in their P concentrations. The proposed work will accomplish two specific objectives: 1.) Determine the soil P speciation, mineralogical and bulk elemental compositions as a function of rock-derived P and land-use type; and 2.) Identify the locations of phosphate groups in soil organic matter coatings and films associated with soil mineral surfaces as a function of rock-derived P and land-use type. Using the requested EMSL resources, we will determine the P molecular composition within isolated SOM components and associated mineral and elemental compositions through the use of nuclear magnetic resonance spectroscopy, inductively coupled plasma mass spectroscopy, and quantitative X-ray diffraction (Objective 1). Additionally, requested resources will provide nano- to micron-scale quantification of the concentrations and location of P in SOM coatings and films in association with other biocritical elements and soil minerals using electron microscopy and X-ray fluorescence and time of flight secondary ion mass spectrometry (Objective 2). The requested EMSL resources are needed establish the importance of P in supporting SOM stabilization on soil mineral surfaces relative to other biocritical nutrients (e.g., N, S, and K), as well as the extent to which the relationship between the belowground C and P cycles is altered by human land use.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2021-10-01
End Date
2023-12-31
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)