|ABDELRAHMAN, HAMADA - Cairo University|
|Olk, Daniel - Dan|
|VENTRELLA, DOMENICO - Italian Agricultural Research Council|
|COCOZZA, CLAUDIO - Bari University|
Submitted to: Journal of Soils and Sediments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2016
Publication Date: 5/6/2016
Citation: Abdelrahman, H., Olk, D.C., Dinnes, D.L., Ventrella, D., Cocozza, C. 2016. Occurrence and abundance of carbohydrates and amino compounds in sequentially extracted labile soil organic matter fractions. Journal of Soils and Sediments. 16(10):2375-2384. doi: 10.1007/s11368-016-1437-y.
Interpretive Summary: Carbon in the soil plays important roles in soil performance, so measuring soil carbon can help identify better practices of land management. However, some carbon lasts in the soil for decades to centuries, while other carbon cycles over weeks to months. Therefore researchers should distinguish old carbon from young carbon when studying how land management affects soil carbon. Several methods have been proposed for separating soil carbon into younger and older fractions, but the compositions of these fractions have not been studied adequately to demonstrate which fractions are truly young or old. Here we found that two fractions claimed to be young were indeed composed of mostly plant-derived materials, supporting their young age. A third fraction was found to have greater proportions of materials from microbial origin, consistent with the belief that this fraction is slightly older and therefore slower in response to land management changes. These findings support further use of these three fractions to study the effect of land management on relatively active fractions of soil carbon that differ slightly in their ages. These results will benefit researchers who study the effects of land management on young fractions of soil carbon or who study the types of carbon found in soil.
Technical Abstract: This study aimed to investigate the content of carbohydrates and amino compounds in three labile fraction of soil organic matter (SOM). Soil samples were collected from two agricultural fields in southern Italy and the light fraction (LF), the 500–53-µm particulate organic matter (POM) and the mobile humic acid (MHA) fraction were sequentially extracted from each soil sample. Seven neutral sugars and 19 amino compounds were extracted and determined from the soil, the light fraction, 500–53 um POM and the MHA. The MHA contained less carbohydrate than the LF or the POM but its carbohydrates was rather of microbial origin, as revealed by the Man/Xyl ratio. The amino compounds in the labile fractions were less in the LF and the POM than in the MHA, while the fungal AAs (aspartic and serine) and bacterial AAs (Alanine and Glycine) were more abundant in the MHA than in the LF or the 500–53-µm POM, which confirms the microbial origin of the MHA. The changes in carbohydrate and amino compound contents in the SOM labile fractions depicted a segment of the decomposition continuum of SOM in soil and can help explain the cycling pattern of these fractions in response to land use and/or management.