FTIR spectroscopy of peat in and bordering Scots pine woodland: relationship with chemical and biological properties

Rapid methods of analysis, such as infrared spectroscopy, have advantages where chemical or biological analyses are time-consuming or require fresh material. FTIR (Fourier transform infrared) spectroscopy gives information on specific functional chemical groups present in organic matter. However, the whole spectrum may also contain information that relates to more general chemical or biological properties. Peat samples were taken along a transect from moorland, through a wetter bog area, into native pine at Abernethy Forest, Scotland. FTIR spectra were determined in addition to other chemical, physical and microbiological properties. Canonical variate analysis showed that the FTIR spectra of the peat from three major vegetation zones were significantly different. Partial least squares (PLS) analysis gave a good correlation between the zero-order FTIR spectra and physical/chemical properties such as pH (variance accounted for, r2=78%), ash (r2=69%) and total N (r2=60%). In particular, the regions in the spectrum corresponding to two secondary amide groupings explained much of the variation in total N. Correlations with biological parameters were poorer except for microbial biomass C (r2=75%) and total phospholipid fatty acids (r2=65%). However, the PLS models were not suitable for predicting the chemical and microbiological properties of the moorland and forest peat soils investigated in this study reliably.