9000 years of changes in peat organic matter composition in Store Mosse (Sweden) traced using FTIR‐ATR

Abstract

Store Mosse (the 'Great Bog' in Swedish) is one of the most extensive bog complexes in southern Sweden (~77 km 2 ), where pioneering palaeoenvironmental research has been carried out since the early 20th century. This includes, for example, vegetation changes, carbon and nitrogen dynamics, peat decomposition, atmospheric metal pollution, mineral dust deposition, dendrochronology, and tephrochronology. Even though organic matter (OM) represents the bulk of the peat mass and its compositional change has the potential to provide crucial ecological information on bog responses to environmental factors, peat OM molecular composition has not been addressed in detail. Here, a 568-cmdeep peat sequence was studied at high resolution, by attenuated reflectance Fourier-transform infrared spectroscopy (FTIR-ATR) in the mid-infrared region (4000-400 cm -1 ). Principal components analysis was performed on selected absorbances and change-point modelling was applied to the records to determine the timing of changes. Four components accounted for peat composition: (i) depletion/accumulation of labile (i.e. carbohydrates) and recalcitrant (i.e. lignin and other aromatics, aliphatics, organic acids and some N compounds) compounds, due to peat decomposition; (ii) variations in N compounds and carbohydrates; (iii) residual variation of lignin and organic acids; and (iv) residual variation of aliphatic structures. Peat decomposition showed two main patterns: a long-term trend highly correlated to peat age (r = 0.87), and a short-term trend, which showed five main phases of increased decomposition (at ~8.4-8.1, ~7.0-5.6, ~3.5-3.1, ~2.7-2.1 and ~1.6-1.3 ka)mostly corresponding to drier climate and its effect on bog hydrology. The high peat accumulation event (~5.6-3.9 ka), described in earlier studies, is characterized by the lowest degree of peat decomposition of the whole record. Given that FTIR-ATR is a quick, nondestructive, cost-effective technique, our results indicate that it can be applied in a systematic way (including multicore studies) to peat research and provide relevant information on the evolution of peatlands.

Postglacial peatland vegetation succession in Store Mosse bog, south‐central Sweden: An exploration of factors driving species change

“…The first was a long‐term trend highly correlated to peat age (Martinez‐Cortizas et al . 2021). The second, short‐term changes showed periods of increased decomposition that largely corresponded to drier climate periods and subsequent effects on bog hydrology (Martinez‐Cortizas et al .…”

Investigating the Mineral Composition of Peat by Combining FTIR-ATR and Multivariate Analysis

“…The spectra of the bulk peat and ashed samples, as well as their standard deviation spectra, are depicted in Figure 2. The peat spectra are dominated by vibrations typical of organic compounds: high absorbance in the regions 3400-3200 cm −1 , 3000-2800 cm −1 , 1800-800 cm −1 and <600 cm −1 , characteristic of polysaccharide, aliphatics, lignin and other aromatics, and nitrogen compounds and organic acids, as recently synthesized for a peat core from a boreal peatland ( [21] and references therein). The standard deviation spectra show that variability between samples is larger for the OH region (3400-3200 cm −1 ), aliphatics (2920 and 2850 cm −1 ), aromatics (1600-1400 cm −1 ), and polysaccharides (1100-1000 cm −1 ).…”

“…Average, standard deviation, and second derivatives of spectra, as well as peak identification and quantification, were computed using the {andurinha} R package [47]. Assignment of vibrations to compounds and minerals was based on the literature (for example, [21,25,48]) and was performed by including reference spectra of the main minerals common to the (granitic) geology of the study area. The reference spectra were obtained from the RRUFF database (http://rruff.geo.arizona.edu/ accessed on 25 January 2021) and also processed with {andurinha} to identify the relevant peaks (Table A1).…”

“…This is one of the reasons why in many investigations the mineralogical composition has been approached through indirect approximations such as elemental analysis (e.g., [14]). One alternative approach is to use infrared spectroscopy, a quick, nondestructive, and affordable technique that can provide information on both organic [15][16][17][18][19][20][21] and inorganic [22][23][24][25][26][27][28]) components simultaneously, which is of great value for environmental studies [29]. Attenuated total reflectance Fouriertransform infrared spectroscopy (FTIR-ATR) in particular, is adequate for this purpose, as it requires a minimum of processing.…”

“…In recent years, FTIR analysis of bulk peat has demonstrated its potential for obtaining paleoenvironmental proxies of peat decomposition (e.g., [21,[38][39][40][41][42]), which, in turn, can be linked with climate and vegetation change. However, the potential of FTIR analysis of peat to infer peat mineral properties remains unexplored.…”