Diverse Soil Carbon Dynamics Expressed at the Molecular Level. Issue 23 (5th December 2017)

• Record Type: Journal Article
• Authors: van der Voort, T. S.; Zell, C. I.; Hagedorn, F.; Feng, X.; McIntyre, C. P.; Haghipour, N.; Graf Pannatier, E.; Eglinton, T. I.
• Is Part Of: Geophysical research letters. Volume 44:Issue 23(2017)
• Page Start: 11, 840
• Page End: 11, 850
• Publication Date: 2017-12-05
• Subjects: soil organic matter (SOM) -- radiocarbon -- biomarker -- compound‐specific -- dissolved organic carbon (DOC); Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2017GL076188
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: The stability and potential vulnerability of soil organic matter (SOM) to global change remain incompletely understood due to the complex processes involved in its formation and turnover. Here we combine compound‐specific radiocarbon analysis with fraction‐specific and bulk‐level radiocarbon measurements in order to further elucidate controls on SOM dynamics in a temperate and subalpine forested ecosystem. Radiocarbon contents of individual organic compounds isolated from the same soil interval generally exhibit greater variation than those among corresponding operationally defined fractions. Notably, markedly older ages of long‐chain plant leaf wax lipids ( n ‐alkanoic acids) imply that they reflect a highly stable carbon pool. Furthermore, marked 14 C variations among shorter‐ and longer‐chain n ‐alkanoic acid homologues suggest that they track different SOM pools. Extremes in SOM dynamics thus manifest themselves within a single compound class. This exploratory study highlights the potential of compound‐specific radiocarbon analysis for understanding SOM dynamics in ecosystems potentially vulnerable to global change. Plain Language Summary: Soil carbon forms the largest amount of organic carbon stored on land. In the context of climate change, it is important to know how stable the carbon in this large reservoir is. In this paper we try to attain a better understanding of the stability of soil carbon in a warm and cold area by looking at specific molecules (soil lipids). By measuring the age of these molecules (using radiocarbon) and comparing it to all environmental information, we attain more insight into the soil carbon stability. We found that the molecules show a wide range of ages, indicating they reflect a wide range of sources. These molecular markers may constitute a cleaner method to assess carbon stability than methods that were used previously. They can also indicate the contribution of extremely old (fossil) carbon derived from carbon‐holding rocks. Altogether, this paper presents a new approach to tackle soil carbon stability and showcases new insights gained from this approach. Key Points: Lipid biomarkers exhibit a larger spread in radiocarbon signatures than observed across operationally defined soil organic matter pools Specific compounds reflect inputs from specific biological sources (microbial, plant derived) Biomarker isotopic signatures reveal geogenic and biogenic carbon contributions to soil organic matter