Structural composition of organic matter in particle-size fractions of soils along a climo-biosequence in the main range of Peninsular Malaysia

Abstract

Information on structural composition of organic matter (OM) in particle-size fractions of soils along a climo-biosequence is sparse. The objective of this study was to examine structural composition and morphological characteristics of OM in particle-size fractions of soils along a climo-biosequence in order to better understand the factors and processes a ecting structural composition of soil organic matter. To explore changes in structural composition of OM in soils with di erent pedogenesis, the A-horizon was considered for further analyses including particle-size fractionation, solid-state C nuclear magnetic resonance (NMR) spectroscopy and scanning electron microscopy (SEM). Due to the increase in the thickness of organic layer with increasing elevation, the A-horizon was situated at greater depth in soils of higher elevation. The relationship between relative abundances of carbon (C) structures and particle-size fractions was examined using principal component analysis (PCA). It was found that alkyl C (20.1-73.4%) and O-alkyl C (16.8-67.7%) dominated particle-size fractions. The proportion of alkyl C increased with increasing elevation, while Oalkyl C showed an opposite trend. Results of PCA conrmed this nding and showed the relative enrichment of alkyl C in soils of higher elevation. Increase in the proportion of alkyl C in 250-2000 µm fraction is linked to selective preservation of aliphatic compounds derived from root litter. SEM results showed an increase in root contribution to the 250-2000 µm fraction with increasing elevation. For the <53 µm fraction, pedogenic process of podzolization is responsible for the relative enrichment of alkyl C. This study demonstrates that changes in structural composition of OM in particle-size fractions of soils along the studied climo-biosequence are attributed to site-speci c di erences in pedogenesis as a function of climate and vegetation.

Chemical and Spectroscopic Investigation of Different Soil Fractions as Affected by Soil Management

“…This was in line with other papers [38][39][40][41] showing that phyllosilicates (kaolinite, chlorite, smectite, illite) are the main components of the clay fraction of soils. The peak at 2927 cm −1 , ascribed to the stretching of the aliphatic C-H group, was evident only in the A fraction, and could be due to the signal of organic matter consisting of labile plant residues [42]. Additionally, in this case, this peak can be highlighted by removing minerals through HF treatment [43].…”

Distribution of nitrogen storage in density and size fractions varied with tillage practices and cropping systems with residue return in black soil of Northeast China

“…As newly incorporated and partially decomposed plant debris of soil, LF is the most sensitive fraction to agricultural management (Ramnarine et al., 2014). The LF together with sand‐size fraction of SOM was often considered as particulate organic matter (POM) (Jafarzadeh‐Haghighi et al., 2016). Tillage practice under MP can destroy soil aggregate structure and release physically protected N (Fernández‐Ugalde et al., 2009), thereby accelerating the decomposition of relatively labile N pool.…”

Nitrogen storage in density and size fractions varied with tillage practices and cropping systems under residue return

“…As newly incorporated and partially decomposed plant debris of soil, LF is the most sensitive fraction to agricultural management (Whalen et al, 2000;Ramnarine et al, 2015). LF together with sand-size fraction was often considered as particulate organic matter (POM) which was derived from plant residues (Jafarzadeh-Haghighi et al, 2016). Tillage practice under MP, like ploughing, can disrupt soil aggregate structure and release physically protected N (Fernandez-Ugalde et al, 2009), thereby accelerating the decomposition of relatively labile N pool.…”