CPMAS 13C NMR Characterization of Leaves and Litters from the Reafforestated Area of Mustigarufi in Sicily (Italy)

Abstract

Reafforestation is generally based on the planting of exotic fast growing tree species suitable for adapting to even harsh environments. Once the introduced plants ameliorate soil conditions, they can be progressively replaced by autochthonous plant species. Reafforestation is applied worldwide. However, only few studies on the effect of reafforestation on lands from Mediterranean regions are available. This paper reports the characterization by cross polarization 13C NMR spectroscopy of fresh leaves and superficial litters from a reafforestated area in central Sicily (Italy). NMR assignment is attempted. A differentiation among the molecular systems within leaves and litters is also done on the basis of NMR assessment. Results showed that the main differences among the leaves of four forest trees (two eucalyptus spp., one cypress sp. and one pine sp.) occur in the distribution of the aromatic and alkyl carbons. In particular, the alkyl moieties in the eucalyptus spp. leaves were attributed to branched structures belonging to the eucalyptus oil, whereas linear fatty acids were more representetive in the NMR spectra of pine and cypress leaves. In addition, the aromatic carbons of the conifer leaves were assigned not only to lignin- and tannin-like structures, but also to common olefin carbons in unsaturated fatty acids and abietic acid-like systems. The spectra of the litters resembled, as expected, those of the leaves. However, the presence of very large carbohydrate NMR signals suggested that degradation processes were still ongoing in litters. A comparative evaluation of CPMAS 13C NMR spectra was done by applying principal component analysis. This paper confirmed the suitability of CPMAS 13C NMR spectroscopy in evaluating the differences among natural bio-masses which are the major nutrient sources for soil micro-organisms and the main input for humification processes.