Non-Protein Nitrogen Compounds Associated with Particles of Vascular Plant Detritus

Abstract

The nitrogen increase which often accompanies the initial stages of vascular plant decomposition cannot be attributed solely to an increase in microbial protein. Evidence from litter bag experiments carried out in terrestrial, freshwater and estuarine environments indicates that as much as 30% of the nitrogen content of aged detritus may exist in the form of non-protein nitrogen compounds. Possible sources of these compounds include: (1) amino sugars such as glucosamine and chitin, (2) complexes such as phenol-protein, protein-lignin or protein-chitin, (3) complexes of inorganic clays and amino groups, and (4) nitrogen containing humic acids. Chitin, presumably originating from fungal cell walls was shown to constitute from 25 to 50% of the non-protein nitrogen contained in detritus which had decomposed under aerobic conditions. It is suggested that these non-protein nitrogen containing compounds, because of their resistance to chemical degradation, may not be easily digested and assimilated by many detritivores. This, in turn, may raise questions concerning the usefulness of detrital C/N ratios as food value indicators.