Climate change impacts on amino acid production and gross mineralization in heathland soil

Louise C. Andresen1, Samuel Bode2, Albert Tietema3, Pascal Boeckx2, Tobias Rütting1
1 Department of Earth Sciences, University of Gothenburg, Sweden
2 Isotope Bioscience Laboratory - ISOFYS, Ghent University, Belgium
3 Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, The Netherlands

O 10.1 in Links between the N cycle and other elements

17.07.2014, 11:40-12:00, H20

The effect of changing climate on the terrestrial N-cycle is still poorly understood. In this study we aimed to assess the effect of drought and increasing temperatures on the fate of organic N within this N-cycle. Our study sites were located in the Oldebroekse heide (52°24′N 5°55′E) is an old managed Dutch Calluna heathland, developed on coversand at fluvioglacial deposits. The ecosystem is characterized by high N deposition (20 kg N ha-1 yr-1, mainly anthropogenic) and leaching (18 kg N ha-1 yr-1). The field site had three 4×5 m plots with precipitation removal during summers and three 4×5 m plots with passive night-time curtains for warming (+0.5 to 1.5 °C), during 14 years prior to the soil sampling.

Here we combine the amino acid and ammonium 15N pool-dilution techniques in order to: 1) assess amino acid production rate relative to gross mineralization rate, and 2) compare amino acid mineralization (NH4+ production from amino acids) with total gross N mineralization.

The amino acid turnover time in the soil was about two minutes. The gross amino acid production for five amino acids was: 33 µg N g-1 day-1, and we observed that the amino acid production reduced by 80% in drought treatment and by 60% in warming treatment. By contrast, the gross mineralization rate doubled in drought treatment. The gross ammonium production rate from amino acids comprised 20% of the total gross NH4 mineralization.

The amino acid production rate is thus important for the gross NH4 mineralization, which suggests a tight link between organic and inorganic N cycling of this soil. Our results show, that gross mineralization during drought events will exhaust the soil nitrogen supply, as the responses of two processes diverge. This suggests that mineralization and availability for plants of inorganic N will potentially reach a limit, at future frequent drought events.

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last modified 2014-06-19