Organic matter, carbon, and humic acids in rehabilitated and secondary forest soils

Lee, Yit Leng (2008) Organic matter, carbon, and humic acids in rehabilitated and secondary forest soils. [Project Paper]

Text lp FSPM 2008 26.pdf Download (4MB)

Abstract

Tropical rainforests cover about 19.37 million ha (60%) of Malaysia's total area and about 8.71 million ha can be found in Sarawak, Malaysia. Excessive logging, mining, and shifting cultivation contribute to deforestation in Sarawak. The objectives of this study were to: (i) Quantify soil organic matter (SOM), soil organic carbon (SOC), and humic acids (HA) in rehabilitated and secondary forest soils, and (ii) Compare SOM, SOC, and HA sequestrations of both forests nt 0-15 cm and 15-30 cm depths. Soil samples were taken at 0-15 cm and 15-30 cm depths from rehabilitated and secondary forests located at Universiti Putra Malaysia, Bintulu Campus. Standard procedures were used to analyze the soil samples for bulk density, pH, texture, C (%), OM (%), N (%}, C/N ratio, yield of HA (%). E4/E6, carboxylic-COOH, phenolic-OH, and total acidity. Carbon sequestered in the stated depths were quantified using standard procedures. Generally, the soil pH (1 M KCI and water) of the rehabilitated and secondary forests were similar regardless of depth. The texture of the rehabilitated forest soil was clayey (clay loam) compared to secondary forest soil (sandy clay loam). The bulk densities of the two forest soiIs increased down the soil profile but no significant difference were observed between these forest soils. Regardless of forest soil type and depth, the C (%) were similar and the fact that except for 15-30 cm of the sccondary forest soil whereby the quantity of C sequestered was significantly lower than that of the rehabilitated forest soil, C sequestration was similar irrespective of forest type and depth. Nevertheless, stable C sequestered in HA were generally higher in the rehabilitated forest soil compared to the secondary forest soil. This was attributed to higher yield of HA in the rehabilitated forest soil, The C/N ratios of the forest soils increased with increasing depth suggesting more humification at 0-15 cm than 15-30 cm. The humification level of the two forest soils at 0-15 cm were similar but that of the rehabilitated forest soil was much humified at 15-30 cm compared to the secondary forest soiI. The E4/E6, carboxylic-COOH. phenolic-OH, and total acidity of both forest soils were generally within the ranges reported by other authors. The SOM and amount of unstable C sequestered in the rehabilitated and secondary forest soils were similar but the stable C sequestered by HA was significantly higher in the rehabilitated forest soil compared to the secondary forest soil irrespective of depth. Hence, the finding suggest that the stability of C in HA realistically reflects C sequestration. This is partly because quantity of stable C depends on the amount of HA.

Item Type:	Project Paper
Subjects:	Q Science > QD Chemistry S Agriculture > S Agriculture (General) S Agriculture > SD Forestry
Faculty:	Faculty of Agriculture and Food Sciences
Depositing User:	Ms. Hairoon Juhaili
Date Deposited:	11 May 2026 01:31
Last Modified:	11 May 2026 01:31
URI:	http://psaspb.upm.edu.my/id/eprint/2746

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