The relationship between microbial carbon and the resource quality of soilcarbon

The biological health of soil is an important aspect of soil quality becaus e of the many critical functions performed by organisms in soil. Various in dicators of soil quality have been proposed, but measurements of microbial biomass are most commonly used. During decomposition of plant residues in s oil the relative intensities of the O-alkyl-C signal decreases and the alky l-C signal increases in nuclear magnetic resonance (NMR) spectra This leads to the suggestion that the alkyl-C to O-alkyl-C ratio of a soil may indica te the degree of decomposition. Consequently, the overall resource quality of soil C as a substrate for heterotrophic microorganisms may be inversely related to the alkyl-C to O-alkyl-C ratio. Our hypothesis is that a relatio nship exists between the size of the soil microbial community (microbial bi omass) and the quality of soil carbon as a resource for microorganisms. New data have been combined with previously published data to show that there was a significant, negative correlation between the biomass C to total C (C -mic to C-org) ratio and the alkyl-C to O-alkyl-C ratio (p < 0.01), which s upports our hypothesis.