However, a number of reports have observed a decrease in the S/G ratio in waterlogged wood , while others have reported no change in the ratio . A decrease in the S/G ratio can be caused by either selective removal of syringyl-rich cell walls or demethoxylation (i.e., formation of guaiacyl units) without any depolymerization of the lignin . The selective removal of a syringyl-rich component (e.g., by WRF) would also produce a corresponding increase in the Ac/Al ratio whereas demethoxylation alone would not affect the Ac/Al ratio (e.g., by bacteria or SRF). THM-GC-MS studies of wood degradation over any timescale are scarce: a major work spanned from 8000 BP to the sixth century, but did not consider the influence of differing environments: samples were taken from marine, freshwater and above-ground environments . In a 5 year study of fungal degradation of oak, intentional, controlled fungal degradation of oak showed S/G decreased over 2 years, while Ac/AlS and Ac/AlG increased over the same timescale . Pyrolysis-GC-MS studies have determined the stability of guaiacyl components of various oak species over centuries .