SEASONAL DIAGENESIS OF ORGANIC MATTER IN POREWATER OF A POOR FEN

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: MCINTIRE-STENNIS
• Reporting Frequency: Annual
• Accession No.: 1014920
• Project Start Date: Jan 8, 2018
• Project End Date: Sep 30, 2020
• Program Code: [(N/A)]- (N/A)

Recipient Organization
MICHIGAN TECHNOLOGICAL UNIV
1400 Townsend Drive
HOUGHTON,MI 49931

Performing Department
College of Forest Resources and Environmental Science

Non Technical Summary
Peatland ecosystems in cold regions of the Earth are rich in organic matter. As global temperatures rise, the variety of plants inhabiting these regions will change, which will affect the decomposition of organic matter and likely accelerate emissions of carbon dioxide and methane from the surface. Increasing emissions of carbon dioxide and methane from peatlands will lead to additional global warming. Thus, it is essential to measure the rates of organic matter decomposition in peatlands and relate decomposition rates to emissions of carbon dioxide and methane from the surface. The results of the study will be disseminated to the scientific community through presentations at meetings and publication of results in the peer-reviewed literature. The findings will be incorporated into classroom materials.

Animal Health Component

40%

Research Effort Categories

Basic

60%

Applied

40%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
102	0330	2000	100%

Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships;

Subject Of Investigation
0330 - Wetland and riparian systems;

Field Of Science
2000 - Chemistry;

Keywords

peatland ecosystems

dissolved organic matter decomposition

carbon dioxide and methane emissions

Goals / Objectives
The principal objective of the proposed study is to advance understanding of the seasonal transformations of dissolved organic matter (DOM) in porewater of peatland ecosystems. Peatlands in high-latitude regions are rich in OM and contain ~19% of global soil OM. As global temperatures rise, water tables of peatlands are expected to descend with concomitant changes in the relative abundance of plant functional types. For example, sedges are expected to be replaced by ericaceous shrubs as global temperatures increase. Plant functional type affects DOM decomposition and gaseous emissions of carbon dioxide and methane by regulating litter quality, rhizosphere oxygen availability, nutrient acquisition pathways, and root symbiosis. Carbon dioxide and methane contribute to global warming. Thus, examining rates of DOM decomposition in peatland plots dominated by various plant functional types is required to predict changes in carbon dioxide and methane emissions from peatland ecosystems under a warming scenario.

Project Methods
The study will be conducted at an extensive poor fen in Nestoria, Michigan, USA (46.34?N 88.16?W). The poor fen has been manipulated to produce several sedge- and ericaceae-only plots. Porewater will be collected from slotted sections of piezometers at depths of 20 and 40 cm bi-monthly immediately after snowmelt and monthly into the fall to study seasonal variations of DOM composition. Seasonal variations of carbon dioxide and methane emissions will be determined by the chamber technique. Porewater samples will be analyzed for inorganic species that catalyze abiotic transformations of DOM and inorganic and organic nitrogen species that regulate biotic transformations of DOM. Ultra-high-resolution mass spectrometry will be used for comprehensive molecular characterization of the DOM. Three-dimensional van Krevelen diagrams will be constructed to visualize biotic and abiotic transformations.

Progress 01/08/18 to 09/30/20

Outputs
Target Audience:The manuscripts developed form the Ph.D. thesis dissertation are directed to the scientific community that is interested in effects of climate change on wetlands, particularly those at high latitudes. Findings from the research will also be incorporated into biogeochemistry courses to provide students with the latest developments in wetland biogeochemistry. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The project has provided training and professional development of a graduate student in environmental biogeochemistry. How have the results been disseminated to communities of interest?The results will be disseminated to communities of interest through publication of the results in the peer-reviewed literature. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Strong seasonal variations of dissolved organic matter (DOM)composition and interactions between day-of-the-year (DOY)and plant functional group (PFG) were observed. The composition of the DOM was regulated on a seasonal time scale by fresh inputs from sedge and Ericaceae, microbial decomposition of labile OM, and accumulation of refractory organic compounds. There appeared to be some evidence of the early stages of humification on the seasonal time scale, i.e., reaction of phenolic moieties of lignin species with amino sugars and complexation of proteinaceous substances by tannin-like species. Concentrations of total dissolved organic carbon (TDOC) were a minimum in May when melting snow flushed DOM characterized by a low average MW and high aromaticity through the fen. Late in the season unique molecular species were likely contributed by root exudates and leaf fall that produced DOM with little aromaticity. Contributions of tannin- and lignin-like compounds to the plot-type indicators in the Ericaceae-only plots were high and likely attributed to inputs of the woody biomass of Ericaceae. Refractory compounds that persisted in the Ericaceae rhizosphere may arise from a combination of anoxia and suppression of free-living saprotroph activity by the ERM fungi. Sedge-only plots exhibited the highest concentrations of TDOC and proteinaceous species throughout the field experiment. The abundance of total phenolic hydrocarbons in sedge-only plots are likely attributed to rapid decomposition of labile compounds in the O2-rich microenvironment surrounding sedge roots, which allowed more refractory compounds like lignin and tannin to accumulate.

Publications

• Type: Journal Articles Status: Submitted Year Published: 2021 Citation: Molecular biogeochemistry of a poor fen. I. Seasonal effects of plant functional groups on dissolved organic matter in porewater, to be published in Biogeochemistry. Molecular biogeochemistry of a poor fen. II. Seasonal effects of plant functional groups on dissolved nitrogen species composition in porewater, to be published in Biogeochemistry. Molecular biogeochemistry of a poor fen. III. Organic matter composition of peat, to be published in Biogeochemistry.

Progress 10/01/18 to 09/30/19

Outputs
Target Audience:The manuscripts developed from the thesis dissertation are directed to the scientific community that is interested in the effects of climate change on wetlands, particularly those at high latitudes. The findings will also be important to scientists interested in sustaining our wetland resources. Findings from the research will also be incorporated in biogeochemistry courses to provide students with the latest developments in wetland biogeochemistry. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The project has provided training and professional development of a graduate student in environmental biogeochemistry. How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?Two more manuscripts will be developed from the thesis dissertation, which will allow dissemation of the data to the scientific community. The second paper will discuss the fixation of nitrogen into the dissolved organic matter of the porewater. The third manuscript will discuss variations in the molecular composition of organic matter with depth in the peat as an indicator of humification on decadal scales.

Impacts
What was accomplished under these goals? The first manuscript from the dissertation is in the final stages of preparation and is nearly ready for submission. The manuscript details observations of humification in porewater on a seasonal time scale. Humification is a process that sequesters carbon in refractory compounds. The trend was much stronger in sedge-only plots.

Publications

• Type: Journal Articles Status: Other Year Published: 2020 Citation: Molecular Biogeochemistry of a Poor Fen. I. Seasonal Effects of Plant Functional Groups on Composition of Dissolved Organic Matter in Porewater

Progress 01/08/18 to 09/30/18

Outputs
Target Audience:The manuscripts developed from the thesis dissertation are directed to the scientific community that is interested in the effects of climate change on wetlands, particularly those at high lattitudes. Findings from the research will also be incorporated in biogeochemisty courses to provide students with the latest developments in wetland biogeochemistry. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Development of the project has provided training and professional development of a graduate student in environmental biogeochemistry. How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?More in-depth interprepretation of the data will continue as the thesis is developed into 3 manuscripts for publication, which will allow dissemination of the data to the scientific community. Information from the project will be incorporated into a graduate course in soil biogeochemistry.

Impacts
What was accomplished under these goals? The molecular composiiton of dissolved organic matter collected during an entire growing season was determined. Some evidence of humification, which acts to sequester carbon in refractory compounds,was observed on a seasonal time scale. Considerable fixation of nitrogen into organic forms was observed throughout the growing season. The trend was much stronger for the sedge-only plots.

Publications

• Type: Theses/Dissertations Status: Submitted Year Published: 2018 Citation: Song, Z., Molecular Biogeochemistry of a Poor Fen, Michigan Technological University, Houghton, Michigan, 2018.