Carbon transformations during decomposition of different components of plant leaves in soil

• Published in: Soil biology & biochemistry 2000-03, Vol.32 (3), p.301-314
• Main Authors: Webster, E.A., Chudek, J.A., Hopkins, D.W.
• Format: Article
• Language: English
• Subjects: 13C solid-state NMR; Agronomy. Soil science and plant productions; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; Fundamental and applied biological sciences. Psychology; Lolium perenne; Organic matter; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Scanning electron microscopy; Soil science
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/S0038-0717(99)00153-4

We investigated the effect of lime addition to an upland organic soil on the decomposition of Lolium perenne leaves and isolated fractions of L. perenne leaves in a laboratory experiment lasting 75 d. The L. perenne plants were grown in a 13CO 2-enriched environment and some leaf material was pretreated with ethanol and detergent in order to remove some cell contents and soluble material. The ethanol- and detergent-treated leaves had less alkyl-C, as seen by solid-state 13C nuclear magnetic spectroscopy (NMR), and a greater proportion of cellulose and hemicellulose than the untreated leaves. Solid-state 13C NMR spectroscopy and scanning electron microscopy (SEM) were used to follow aspects of the C transformations during decomposition. C mineralization was estimated from total CO 2 production. The size and activity of the microbial community was greater in limed than in soils without lime, and microbial respiration was less in both soils amended with ethanol- and detergent-treated leaves compared to soils amended with untreated leaves. In both limed and unlimed soils, amendment with untreated leaves led to additional CO 2 production within 7 d of addition, whereas amendment with treated leaves led to a smaller increase in CO 2 production. The flush of CO 2 production was attributed to decomposition of the more accessible and soluble plant components that, in the ethanol- and detergent-treated leaves, had been removed during the ethanol and detergent treatment. The 13C NMR spectra recorded for plant material separated from soil 1 d after addition of ethanol- and detergent-treated leaves had larger alkyl-C (30 ppm) signals compared with spectra from untreated leaves. This was interpreted as representing an accumulation of residues from decomposition of plant structural components.