Changes in Soil Organic Carbon Fractions Across a Loess Toposequence

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ORIGINAL PAPER

Changes in Soil Organic Carbon Fractions Across a Loess Toposequence Arsalan Azam 1 & Mohammad Saleem Akhtar 1 & Shah Rukh 2 & Ayaz Mehmood 3 Ahmad Khan 1 & Abdul Qayyum 5 & Waseem Ahmad 6 & Ali Raza Gurmani 3

&

Muhammad Imran 4 &

Received: 3 October 2019 / Accepted: 20 February 2020 # Sociedad Chilena de la Ciencia del Suelo 2020

Abstract Soil organic carbon fractions may vary with soil development and soil genesis controls its vertical distribution. The objectives of this study were to determine organic carbon fractions in soil derived from loess parent material and the role of relief in its vertical distribution. Five soil pedons, i.e., Typic Ustorthents (Rajar), Typic Calciustepts (Missa), Udic Calciustepts (Basal), Udic Haplustalfs (Guliana), and Typic Hapludalfs (Mansehra), were selected along a loess toposequence and sampled at genetic horizon level. Soils were characterized for texture, pH, calcium carbonate (CaCO3), and organic carbon fractions including total organic carbon (TOC), dissolved organic carbon (DOC), particulate organic carbon (POC), HCl-insoluble organic carbon, and density fractions, i.e., heavy fraction (HF) and light fraction (LF). Total organic carbon content ranged from 0.03 to 0.98% in these soils and significantly differed with soil depth within each soil and soil type. Mansehra and Guliana had 0.04 and 0.031% POC, respectively, which was greater compared to remaining soils. Dissolved organic carbon was greater in the Basal followed by Mansehra, Rajar, Missa, and Guliana soil profiles, and distribution remains uniform throughout the profile’s depth. Insoluble C fraction was 0.214% in Mansehra profiles followed by 0.156% in Rajar, 0.078% in Basal, 0.063% in Guliana, and 0.091% in Missa soil profiles. The Mansehra soil profiles had the highest (0.008 and 0.30%) content of both light and heavy fractions. Total organic carbon had little correlation with clay. Particulate organic carbon, DOC, and HCl-insoluble organic carbon had a significant correlation with TOC. The HF had the strongest correlation with TOC, while LF had a negative correlation. The soil organic fractions significantly differed with soil type and soil genesis. The soils at gentle slopes are dominant in most of the organic carbon fractions due to higher development stage. Keywords Carbon fractions . Loess . Soil development . Carbon distribution

* Ayaz Mehmood [email protected] Arsalan Azam [email protected] Mohammad Saleem Akhtar [email protected] Shah Rukh [email protected] Muhammad Imran [email protected]

Ali Raza Gurmani [email protected] 1

Institute of Soil Science, PMAS Arid Agriculture University, Rawalpindi 46300, Pakistan

2

National Center of Excellence in Geology, University of Peshawar, Peshawar, Pakistan

3

Department of Soil Science, The University of Haripur, Haripur, Pakistan

4

Department of Soil and Environmental Sciences, Ghazi University, Dera Ghazi Khan, Pakistan

5

Department of Agronomy, The University of Haripur, Haripur, Pakistan

6

Department o