Dynamics of Labile Dissolved Organic Matter under Forest Harvest Operation
EMSL Project ID
60518
Abstract
US Forest Service Southern Research Station are implementing a new watershed-scale experiment on the Santee Experimental Forest in South Carolina focusing on longleaf pine restoration. An outbreak of Aphanomyces invadans, which causes epizootic ulcerative syndrome in freshwater fish, was detected in a first-order, freshwater stream that drains an experimental watershed being harvested as the first phase of the longleaf pine restoration. We hypothesize that incidence of fish infection was triggered by poor water quality with significant levels of biodegradable dissolved organic matter (DOM) leaching from debris remained in forest floor after clear-cut operations. In coordinating with the current effort of DOE-Environmental System Science (DOE-EES) Program determining carbon and mercury biogeochemical processes under intensive forest management, we are submitting this limited scope proposal to request instrument time in FT-ICR-MS (24 samples) and 1H-NMR (8 samples) to characterize dissolved organic matter (DOM) in the perturbed watershed. We propose to apply electrospray ionization (ESI) and atmospheric pressure photo ionization (APPI) coupled with 15T FT-ICR MS to determine the molecular composition of DOM. Identified DOM formula will be grouped into amino sugar, carbohydrates, lignin, lipids, etc. based on relative abundance values of counts in C, H, and O. Number of labile compounds using molecular lability boundary (i.e., H/C > 1.5) will also be determined. Selected 8 samples will be further characterized by 1H-NMR using 600 Hz NMR. 1H NMR spectra will be collected with solvent suppression using a modified version of the WATERGATE-W5 or other solvent suppression sequence. Fractional abundances (%) of four major types of DOM components including material derived from linear terpenoids (MDLT), carboxyl-rich alicyclic molecules (CRAM), carbohydrates and peptides, and aromatic will be determined.
Identification of the specific DOM compounds derived from debris in hummock or hollow microtopography and exported from the perturbed watershed after clear-cut operation will advance the understanding of the interrelationships between substrates and anoxia on carbon and mercury cycling. Using EMSL’s state of the art instrumentation for the characterization of these water samples and leveraging EMSL’s expertise we can explain and understand: 1) Does a forest clear-cut operation cause the pulse of biodegradable DOM, deteriorating water quality and triggering the outbreak of Aphanomyces invadans? 2) How long will the changes in DOM chemistry last after a forest operation?
Project Details
Project type
Limited Scope
Start Date
2023-03-20
End Date
2023-06-18
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)