Transformation of <i>n</i>-alkanes from plant to soil: a review

Abstract

Abstract. Despite the importance of soil organic matter (SOM) in the global carbon cycle, there remain many open questions regarding its formation and preservation. The study of individual organic compound classes that make up SOM, such as lipid biomarkers including n-alkanes, can provide insight into the cycling of bulk SOM. While studies of lipid biomarkers, particularly n-alkanes, have increased in number in the past few decades, only a limited number have focused on the transformation of these compounds following deposition in soil archives. We performed a systematic review to consolidate the available information on plant-derived n-alkanes and their transformation from plant to soil. Our major findings were (1) a nearly ubiquitous trend of decreased total concentration of n-alkanes either with time in litterbag experiments or with depth in open plant–soil systems and (2) preferential degradation of odd-chain length and shorter chain length n-alkanes represented by a decrease in either carbon preference index (CPI) or odd-over-even predominance (OEP) with depth, indicating degradation of the n-alkane signal or a shift in vegetation composition over time. The review also highlighted a lack of data transparency and standardization across studies of lipid biomarkers, making analysis and synthesis of published data time-consuming and difficult. We recommend that the community move towards more uniform and systematic reporting of biomarker data. Furthermore, as the number of studies examining the complete leaf–litter–soil continuum is very limited as well as unevenly distributed over geographical regions, climate zones, and soil types, future data collection should focus on underrepresented areas as well as quantifying the transformation of n-alkanes through the complete continuum from plant to soil.

Validating the accuracy of multiple sediment fingerprinting methods

“…This may be due to the change of concentration in the process of long‐chain and short‐chain n‐alkanes transport, resulting in lower prediction accuracy of source contributions. Some studies have proposed that n‐alkanes can be degraded by soil microorganisms (De Pasquale et al, 2012; Schäfer et al, 2016; Thomas et al, 2021). The enrichment or depletion of sediment in the process of transport may also lead to a change in the concentration of n‐alkanes (Li et al, 2020).…”

Biomarker proxies for reconstructing Quaternary climate and environmental change

“…As organic molecules, biomarkers are subject to degradation processes during transport and deposition (e.g. Madureira et al ., 1997; Wakeham et al ., 1997; Thomas et al ., 2001). However, different classes of organic compounds have varying rates of degradation (Arndt et al ., 2013).…”

Changes in organic molecular marker signatures in soils amended with biochar during a three-year experiment with maize on a Fluvisol

“…Fatty acids, and especially phospholipid fatty acids (PLFA) analysis have long been used to study soil microbial community structure and responses to various agricultural management. In studies with anthropogenic soils and or matrices that contain burnt (pyrolyzed) organic matter, however, it has been shown that alkanes distribution brings about detailed and complex view of sources and origin of soil organic matter (SOM), because of their higher hydrophobicity and stability to degradation, and also their use as a proxy to determine past vegetation environments (Atanassova et al, 2012;Eckmeier and Wiesenberg, 2009;Thomas et al, 2021).…”