Variations in soil organic carbon and litter decomposition across different tropical vegetal covers

• Published in: Current science (Bangalore) 2010-10, Vol.99 (8), p.1051-1060
• Main Authors: Dinakaran, J., Krishnayya, N. S. R.
• Format: Article
• Language: English
• Subjects: Acid soils; Aromatics; Bamboos; Forest soils; Organic soils; Plant litter; Soil biochemistry; Soil depth; Soil organic carbon; Soil respiration; Tropical soils
• ISSN: 0011-3891

The present study shows variations in soil organic carbon (SOC) and litter decomposition across different vegetal covers. Tropical vegetal covers occupied by teak, bamboo and mixed species were used for the study. SOC was analysed in the soils up to a depth of 1.25 m at different intervals. Physical fractionation was done in the collected soil samples. Respiration was measured in the soils of the three types in summer, monsoon and winter. Litter-bag experiment was carried out to understand the process of decomposition in the three types of litter at three different depths, viz. top, 25 cm and 50 cm. SOC values from the three different types of vegetal cover showed significant differences. The annual fall of leaf-litter was maximum in mixed vegetal cover followed by teak and bamboo. Litter-bag experiment showed that the litter got decomposed within a year on storage. Higher soil respiration in all the three vegetal covers supports faster rates of decomposition. The decomposition was faster in bags kept at the top layers of the soil compared to the ones in the deeper layers. There was an increase in SOC of samples from the litter-bag study, indicating that tropical soils can absorb additional carbon. Physical fractionation of SOC showed uniformity in the proportions of mobile and recalcitrant pools across soil profiles of the three vegetal covers. A proton NMR study carried out to understand the chemical nature of SOC revealed complete absence of carboxyl group, whose presence is generally reported in the SOC of temperate soils. The groups observed were alkyl, O-alkyl and aromatic. Fluctuations were seen in the proportion of alkyl groups. Uniformity seen in the chemical composition of SOC from the proton NMR study revealed that barring initial steps, decomposition of organic matter would follow more or less the same path in tropical soils, irrespective of differences in plant litter.