La Trobe

Increasing nitrogen availability does not decrease the priming effect on soil organic matter under pulse glucose and single nitrogen addition in woodland topsoil

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Nitrogen (N) availability has been suggested to affect the mineralization of soil organic carbon (C). However, it remains unclear how N supply affects the decomposition of native soil organic C induced by labile C input (i.e., priming effect). This study aimed at examining whether the magnitude and direction of the priming effect depended on the N supply rates and how this interacted with soil layers differing in soil organic C content. Nitrogen was supplied from 0 to 160 mg N kg−1 as Ca(NO3)2 prior to incubation, and 13C-glucose was supplied weekly to induce the priming effect. The priming effect increased with increasing N addition up to 20 mg kg−1, and then plateaued between 20 and 140 mg kg−1 of N addition. In the surface layer of topsoil (0–5 cm), the priming effect at 160 mg N kg−1 decreased by 16% from the peak but was still higher than that in the nil-N control. The effect of N addition on increasing the priming effect lasted for four weeks during which soil mineral N concentrations decreased and the microbial biomass C:N ratio maintained low. By Week 6, N addition stimulated the priming effect to the greatest extent. This N effect was greater in the surface than subsurface layer (5–10 cm) of the topsoil (53% vs. 25%) in the first four weeks but similar afterwards. Our results show that soil organic C in woodland topsoils is susceptible to loss via the N-enhanced priming across a range of N rates.

Funding

YZ received the La Trobe University scholarships, and JJ and CT were supported by Australian Research Council (DP210100775) .

History

Publication Date

2022-09-01

Journal

Soil Biology and Biochemistry

Volume

172

Article Number

108767

Pagination

10p.

Publisher

Elsevier

ISSN

0038-0717

Rights Statement

© 2022. This manuscript version is made available under the CC-BY-NC-ND 4.0 license: https://creativecommons.org/licenses/by-nc-nd/4.0/

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