Molecular characterization of soil organic matter along a soil chronosequence of Midtre Lovenbreen foreland in Svalbard

Abstract

Glacier forelands give an opportunity to study the successional processes in the terrestrial ecosystem along the chronosequence at a time. The newly exposed ground gives chances for plants and microorganisms to be established, and these organisms have contributed in building up soil organic matter (SOM) in this area. To investigate a shift in molecular compositions of newly added SOM along the soil chronosequence, surface soil from nine sites in Midtre Lovenbreen foreland in Svalbard were sampled, representing soil ages of 4, 9, 37, 58, 65, 71, and 78 years (site 1？7, respectively). Two sites outside the moraine (site 8, 9) were selected as a reference site. To obtain a clear picture of newly added SOM's composition, free light fraction (FLF) was separated by density fractionation with sodium polytungstate (1.55 g cm-3). The molecular compositions of FLF were analyzed through pyrolysis-Gas Chromatography/Mass Spectrometry (py-GC/MS) and TMAH (tetramethylammonium hydroxide)-py-GC/MS at two pyrolysis temperatures (350 and 600 °C). In both analyses, SOM characteristics between inside and outside moraine were distinctly separated. However, we could not find clear trend of newly input SOM structure along the chronosequence inside glacier moraine in this study. Our results would help for better understanding of SOM formation and successional processes in a newly exposed soil and investigation of the relationships between SOM composition and vegetation.