What do you want to know exactly? The title of question is asking something and the description is telling something else.

Rakesh Subramanian Srirangarayan DGGE is a fingerprint technique to evaluate microbial structure, which can result in measures of diversity. In order to have a indirect idea of genes related to carbon stocks you could search for primers related to carbon cycling and then quantify the number of copies from those genes (via qPCR, for example). Another way to indirect evaluate that, is to excise the bands, perform cloning and sequence to see the relationship between then and C cycling. You can also perform NGS sequencing (e.g metagenomics) with further search for genes related to carbon cycling. A fourth approach could be the GeoChip technology (developed by Professor Zhou, University of Oklahoma), which will give you an idea about carbon and other cycles, through hybridisation.