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Gewählte Master / Diploma Thesis:

Pia Minixhofer (2015): Impact of extreme weather events on plant available nitrogen and amino acids using microdialysis.
Master / Diploma Thesis - Institut für Bodenforschung (IBF), BOKU-Universität für Bodenkultur, pp 82. UB BOKU obvsg

Data Source: ZID Abstracts
Climate change is predicted to result in more frequent and more intense weather extremes like droughts and severe rainfall. They will have a major impact on biogeochemical nutrient cycles such as the terrestrial nitrogen (N) cycle. The aim of this study was to show the effect of repeated drying and rewetting cycles on plant available concentrations and flux of inorganic (ammonium NH4, nitrate NO3) and organic N (amino acids AA). At the study site in the Rosalia forest, Lower Austria, two stress treatments were simulated between May and October 2014. The stress treatments consisted of either 6 one-month-drying periods (moderate stress MT) or 3 two-month-drying periods (severe stress ST). After the drying periods followed moderate (75 mm) or severe (150 mm) artificial rewetting events. Soil samples were taken every month for pH, microbial biomass carbon (C) and N, NO3-, NH4+, dissolved organic C and N analysis. Additionally, a new microdialysis method was used to assess short-term N fluxes of NO3-, NH4+ and AA. Overall, seasonal variation had a stronger effect on plant-available N than stress treatments. However, results indicated that the degree of stress treatment influenced plant-available NO3-N as measured by microdialysis, such that after irrigation NO3-N was quickly mobilized leading to a concentration peak twice as high in ST than MT. This was not detectable in conventional KCl extracts of soil samples. Surprisingly, before the irrigation the flux of AA-N contributed 71 and 55% to total N flux in MT and ST, respectively. Twenty-four hours later, the importance of AA-N had declined and 70 and 50% of total N flux were contributed by NO3-N. The findings of this study corroborate that N concentrations measured in KCl extracts might not be capable to assess the fast N turnover processes during drying and rewetting of soils, and that amino acids might be more important for plant-available N supply in temperate forest ecosystems than previously thought.

Beurteilende(r): Zechmeister-Boltenstern Sophie

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