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Land-use type and ecosystem disturbances are important drivers for element cycling and bear the potential to modulate soil processes and hence ecosystem functions. To better understand the effect of such drivers on the magnitude and temporal patterns of organic matter (OM) and associated nutrient fluxes in soils, continuous flux monitoring is indispensable but insufficiently studied yet. We conducted a field study to elucidate the impact of land-use and surface fires on OM and nutrient fluxes with soil solution regarding seasonal and temporal patterns analyzing short (<3months) and medium-term (3-12months) effects. Control and prescribed fire-treated topsoil horizons in beech forests and pastures were monitored biweekly for dissolved and particulate OM (DOM, POM) and solution chemistry (pH value, elements: Ca, Mg, Na, K, Al, Fe, Mn, P, S, Si) over one post-fire year. Linear mixed model analyses exhibited that mean annual DOM and POM fluxes did not differ between the two land-use types, but were subjected to strong seasonal patterns. Fire disturbance significantly lowered the annual soil solution pH in both land-uses and increased water fluxes, while DOC fluxes remained unaffected. A positive response of POC and S to fire was limited to short-term effects, while amplified particulate and dissolved nitrogen fluxes were observed in the longer run and co-ocurred with accelerated Ca and Mg fluxes. In summary, surface fires generated stronger effects on element fluxes than the land-use. Fire-induced increases in POM fluxes suggest that the particulate fraction represent a major pathway of OM translocation into the subsoil and beyond. With regard to ecosystem functions, pasture ecosystems were less prone to the risk of nutrient losses following fire events than the forest. In pastures, fire-induced base cation export may accelerate soil acidification, consequently exhausting soil buffer systems and thus may reduce the resilience to acidic depositions and disturbances., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Soil organic matter (SOM) and its water-soluble components play an important role in terrestrial carbon cycling and associated ecosystem functions. Chemically, they are complex mixtures of organic compounds derived from decomposing plant material, microbial residues, as well as root exudates, and soil biota. To test the effect of the ecosystem type (forest and grassland) and fires events on the chemistry of dissolved organic matter (DOM), we applied a combination of laser-desorption/ionization time-of-flight mass spectrometry (LDI-TOF-MS) and 2D ( 1 H and 13 C) nuclear magnetic resonance (NMR) spectroscopy to water-extractable organic matter (WEOM) from a range of top soil samples. The aim was to assess the suitability of LDI-TOF-MS for the rapid characterization of WEOM. Therefore, we evaluated the effects of sample (pH and dilution) conditions and use of positive or negative reflector mode to identify the conditions under which LDI-TOF-MS best distinguished between WEOM from different sources. Thirty-six samples were measured with both analytical techniques and their chemical patterns were statistically evaluated to distinguish firstly the effect of the type of ecosystem (forest versus grassland) on WEOM characteristics, and secondly the impact of fire on the chemical composition of WEOM. The nonmetric multidimensional scaling (NMDS) analysis of the most suitable experimental LDI-TOF-MS conditions showed a clear separation between the type of vegetation and fire-induced changes, mostly reflecting the presence of poly(ethylene glycol) in grassland soils. Discrimination among WEOM from different vegetation types was preserved in the fire treated samples. The calculation of the relative abundance of certain functional structures in the WEOM samples revealed a common composition of forest and grassland WEOM, with polysaccharides and proteins making up to 60%. The compositional impact of forest fire on WEOM was more pronounced compared to the one of grassland, leading to a decline in the main components, and an increase in amino-sugars, fatty acids, and sterols. The recorded 1 H NMR and heteronuclear single quantum coherence (HSQC) spectra showed a decrease of the carbohydrate signal in WEOM from fire-treated samples, which was more pronounced in forest than in grassland soils., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The analysis of synthetic polymers represents today an important part of polymer science to determine their physical properties and to optimize the performance of polymeric materials for block copolymers as well as blend systems. The characterization can easily and rapidly be performed by mass spectrometry. In particular, the film formation of a synthetic polymer is of interest in material research and quality control, which can be determined by employing mass spectrometric imaging (MSI) using secondary ion mass spectrometry (SIMS) or matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. MALDI-MSI has been rapidly improved for the analysis of tissue cross-sections due to its soft ionization and accessible m/z range, which both also play an important role in polymer science. On the other hand, SIMS-MSI enables a sub-micrometer molecular spatial resolution, which is limited in MALDI-MSI due to the spatial resolution capabilities of the laser desorption process. The aim of the present contribution is to summarize recent advances in both imaging techniques for the analysis of synthetic polymers and to highlight their capabilities to correlate several imaging modalities in future applications., (Copyright © 2013 Elsevier B.V. All rights reserved.)