04 Oct 2022
04 Oct 2022
Status: this preprint is currently under review for the journal BG.

Warming accelerates belowground litter turnover in salt marshes – insights from a Tea Bag Index assay

Hao Tang1,2, Stefanie Nolte3,4, Kai Jensen2, Roy Rich5, Julian Mittmann-Goetsch2, and Peter Mueller2,5 Hao Tang et al.
  • 1Key Laboratory of Land Resources Evaluation and Monitoring in Southwest, Ministry of Education, Sichuan Normal University, Chengdu, 610068, China
  • 2Institute of Plant Science and Microbiology, Universität Hamburg, Hamburg, 22609, Germany
  • 3School of Environmental Sciences, University of East Anglia, Norwich, NR47TJ, UK
  • 4Centre for Environment, Fisheries and Aquaculture Science, Pakefield Rd, Lowestoft, UK
  • 5Smithsonian Environmental Research Center, Edgewater, MD 21037, United States

Abstract. Salt marshes play an important role in the global carbon (C) cycle due to the large amount of C stored in their soils. Soil C input in these coastal wetland ecosystems is strongly controlled by the production and initial decomposition rates of plant belowground biomass and litter. This study used a field warming experiment to investigate the response of belowground litter breakdown to rising temperature (+1.5 °C and +3.0 °C) across whole-soil profiles (0–60 cm soil depth) and the entire flooding gradient ranging from pioneer zone via low marsh to high marsh. We used standardized plant materials, following the Tea Bag Index approach, to assess the initial decomposition rate of (k) and the stabilization factor (S) of labile organic matter (OM) inputs to the soil system. While k describes the initial pace at which labile (= hydrolyzable) OM decomposes, S describes the part of the labile fraction that does not decompose during deployment in the soil system and stabilizes due to biochemical transformation. We show that warming strongly increased k consistently throughout the entire soil profile and across the entire flooding gradient, suggesting that warming effects on the initial decomposition rate of labile plant materials are independent of the soil aeration (i.e. redox) status. By contrast, negative effects on litter stabilization were less consistent. Specifically, warming effects on S were restricted to the aerated topsoil in the frequently flooded pioneer zone, while the soil depth to which stabilization responded increased across the marsh elevation gradient via low to high marsh. These findings suggest that reducing soil conditions can suppress the response of belowground litter stabilization to rising temperature. In conclusion, our study demonstrates marked differences in the response of initial decomposition rate vs. stabilization of labile plant litter to rising temperature in salt marshes. We argue that these differences are strongly mediated by the soil redox status along flooding and soil-depth gradients.

Hao Tang et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2022-189', Md. Golam Rakkibu, 26 Oct 2022
  • RC2: 'Comment on bg-2022-189', Inge Althuizen, 24 Nov 2022
  • RC3: 'Comment on bg-2022-189', Anonymous Referee #3, 07 Dec 2022

Hao Tang et al.

Hao Tang et al.


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Short summary
In order to gain a first mechanistic insight into warming effects and litter breakdown dynamics across whole-soil profiles. We used a unique field warming experiment and standardized plant litter to investigate the degree to which rising soil temperatures can accelerate belowground litter breakdown in coastal wetland ecosystem. The central finding is warming strongly increases the initial rate of labile litter decomposition, but has less consistent effects on the stabilization of this material.