University of Natural Resources and Life Sciences, Vienna (BOKU) - Research portal
Gewählte Master / Diploma Thesis:
Vera Luise Baumert
(2016):
Effects of long-term nitrogen deposition on the chemical composition of soil organic matter fractions in two temperate forest soils.
Master / Diploma Thesis - Institut für Bodenforschung (IBF),
BOKU-Universität für Bodenkultur,
pp 40.
UB BOKU
obvsg
- Abstract:
- Anthropogenic nitrogen (N) deposition has greatly increased the availability of reactive N in terrestrial ecosystems over the last decade. Besides causing several environmental problems, the extreme alteration of the global N cycle is expected to interact with the closely linked global carbon (C) cycle. Long-term N addition to forest ecosystems has frequently been reported to cause shifts in soil microbial communities and enzyme activities and impede soil organic matter (SOM) decomposition. This may affect SOM chemistry and increase C sequestration. In this study, the effects of long-term N deposition (~ 20 years) on SOM quality in two temperate Norway spruce forest sites was investigated. The sites located in Denmark and Switzerland have regularly received N additions of 35 kg N ha-1 yr-1 (since 1992) and 30 kg N ha-1 yr-1 (since 1995), respectively. Mineral soil samples were separated by a combined density and particle size fractionation into three fractions that correspond to functional SOC pools of increasing stability: I) particulate organic matter (POM) (> 63 μm, < 1.6 g cm-3), II) silt and clay (s+c) (< 63 μm, > 1.6 g cm-3), and III) sand and aggregates (> 63 μm, > 1.6 g cm-3). The individual fractions were analyzed by mid infrared spectroscopy (MIRS) and pyrolysis-gas chromatography/mass spectrometry (PyGC/MS). Effects of two decades of simulated N deposition on SOM chemistry were much more pronounced in Klosterhede compared to Alptal. This illustrates that individual sites may react very differently to N deposition, depending on N dosage and ecosystem properties. In Klosterhede, the relative abundance of lignin-derived and phenolic compounds generally tended to increase upon N addition, whereas that of aliphatic compounds tended to decrease. N- containing substances and carbohydrates did not respond to N enrichment. Effects were most distinct in the labile POM fraction, proving SOM fractionation a valuable tool when it comes to identifying fractions that react more rapidly to changes in environmental factors or management.
- Beurteilende(r): Zechmeister-Boltenstern Sophie