Litter Quality ofPopulusSpecies as Affected by Free-AirCO2Enrichment and N-Fertilization

Abstract

The effect of elevatedCO2and nitrogen fertilization on the molecular chemistry of litter of threePopulusspecies and associated soil organic matter (SOM) was investigated by pyrolysis-gas chromatography/mass spectrometry. The results are based on 147 quantified organic compounds in 24 litter samples. Litter ofP. euramericawas clearly different from that ofP. nigraandP. alba. The latter two had higher contents of proteins, polysaccharides, and cutin/cutan, while the former had higher contents of phenols and benzofurans/pyrans. The difference between replications was at least as large as the effect of treatments, so that no systematic chemical changes were attributable toCO2effect or N-fertilization effect. The chemistry of SOM under the various species and treatments did not show significant changes either. The low number of available replicates that is two was clearly insufficient to overcome the effect of spatial variation on litter chemistry and detect small differences in molecular litter chemistry.