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United States Department of Agriculture

Agricultural Research Service

Research Project: Management Practices to Mitigate Global Climate Change, Enhance Bio-Energy Production, Increase Soil-C Stocks & Sustain Soil Productivity...

Location: Soil Plant Nutrient Research (SPNR)

Title: Evaluation of angiosperm and fern contributions to soil organic matter using two methods of pyrolysis-gas chromatography-mass spectrometry

Author
item Stewart, Catherine

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 19, 2011
Publication Date: August 16, 2011
Repository URL: http://DOI 10.1007/s11104-011-0927-3
Citation: Stewart, C.E. 2011. Evaluation of angiosperm and fern contributions to soil organic matter using two methods of pyrolysis-gas chromatography-mass spectrometry. Plant and Soil. 351:31-46.

Interpretive Summary: Plant biochemical characteristics influence decomposition rates and subsequently the biochemical composition of soil organic matter. Ferns, in particular have biochemical characteristics that could influence the stability of soil organic matter (SOM), such as high concentrations of aliphatic compounds that are part of the plant cuticle as well as polyphenolics (lignins and tannins). We found distinct differences in lignin biomarkers between the ferns and angiosperms using both methods, although TMAH-py-GC/MS was necessary to observe intact p-coumaryl lignin acids of the ferns. Both py-GC/MS and TMAH-py-GC/MS are compound-specific methods to detect biomarker preservation in ecosystems, but most useful used in tandem for their complimentary results.

Technical Abstract: Plant biochemical characteristics influence decomposition rates and subsequently the biochemical composition of soil organic matter. Ferns, in particular have biochemical characteristics that could influence the stability of soil organic matter (SOM), such as high concentrations of aliphatic compounds that are part of the plant cuticle as well as polyphenolics (lignins and tannins). Despite being an important plant group in many biomes, little is known of whether there are specific biomarkers for ferns that may persist in terrestrial environments. Pyrolysis gas chromatography-mass spectrometry (py-GC/MS) is a method that analyzes biochemical fragments of samples and may be used to infer probable source molecules and structures (i.e. lignin, polysaccharides, lipids). Methylation combined with py-GC/MS improves detection of lignin-derived acids as well as fatty acid methyl esters from lipids. We used both methods (py-GC/MS and TMAH-py-GC/MS) to characterize three fern and two angiosperm species’ live tissues, litter and soils beneath each plant in the Kohala Mountains, Hawaii. Py-GC/MS provided a broad biochemical overview of the samples including lignin, polysaccharide, lipid, and N-bearing compound fragments while TMAH-py-GC/MS provided detailed lignin and lipid-derived fatty acids at the expense of the other categories. We found distinct differences in lignin biomarkers between the ferns and angiosperms using both methods, although TMAH-py-GC/MS was necessary to observe intact p-coumaryl lignin acids of the ferns. Despite known differences in polysaccharide composition between polypod and non-polypod fern clads and angiosperms, we observed no distinct differences in cellulose biomarkers. Large concentrations of plant-derived epicuticular waxes were evident in the live tissues of all samples yet we observed no selective preservation of these compounds in soils beneath the ferns. Polypod ferns as well as the angiosperms contained aromatic compounds that distinguished the species’ live tissue and litter, and some soils. Both py-GC/MS and TMAH-py-GC/MS are compound-specific methods to detect biomarker preservation in ecosystems, but most useful used in tandem for their complimentary results.

Last Modified: 12/19/2014
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