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Title: Biochemical and structural controls on the decomposition dynamics of boreal upland forest moss tissues

Abstract

Mosses contribute an average of 20 % of boreal upland forest net primary productivity and are frequently observed to degrade slowly compared to vascular plants. If this is caused primarily by the chemical complexity of their tissues, moss decomposition could exhibit high temperature sensitivity (measured as Q 10) due to high activation energy, which would imply that soil organic carbon (SOC) stocks derived from moss remains are especially vulnerable to decomposition with warming. Alternatively, the physical structure of the moss cell-wall biochemical matrix could inhibit decomposition, resulting in low decay rates and low temperature sensitivity. We tested these hypotheses by incubating mosses collected from two boreal forests in Newfoundland, Canada, for 959 days at 5°C and 18°C, while monitoring changes in the moss tissue composition using total hydrolyzable amino acid (THAA) analysis and 13C nuclear magnetic resonance (NMR) spectroscopy. Less than 40 % of C was respired in all incubations, revealing a large pool of apparently recalcitrant C. The decay rate of the labile fraction increased in the warmer treatment, but the total amount of C loss increased only slightly, resulting in low Q 10 values (1.23–1.33) compared to L horizon soils collected from the same forests. NMR spectra weremore » dominated by O-alkyl C throughout the experiment, indicating the persistence of potentially labile C. The accumulation of hydroxyproline (derived primarily from plant cell-wall proteins) and aromatic C indicates the selective preservation of biochemicals associated with the moss cell wall. This was supported by scanning electron microscope (SEM) images of the moss tissues, which revealed few changes in the physical structure of the cell wall after incubation. This suggests that the moss cell-wall matrix protected labile C from microbial decomposition, accounting for the low temperature sensitivity of moss decomposition despite low decay rates. Climate drivers of moss biomass and productivity, therefore, represent a potentially important regulator of boreal forest SOC responses to climate change that needs to be assessed to improve our understanding of carbon–climate feedbacks.« less

Authors:
ORCiD logo [1];  [1];  [2];  [3];  [4];  [1]
  1. Memorial Univ., St. John’s, NL (Canada). Dept. of Earth Sciences
  2. Univ. of Kansas, Lawrence, KS (United States). Kansas Biological Survey, Dept. of Ecology and Evolutionary Biology
  3. Univ. of South Carolina, Columbia, SC (United States). Marine Science Program, Dept. of Biological Sciences
  4. Canadian Forest Service, Atlantic Forestry Centre, NL (Canada). Natural Resources Canada
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1506777
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Biogeosciences (Online)
Additional Journal Information:
Journal Name: Biogeosciences (Online); Journal Volume: 15; Journal Issue: 21; Journal ID: ISSN 1726-4189
Publisher:
European Geosciences Union
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 59 BASIC BIOLOGICAL SCIENCES

Citation Formats

Philben, Michael, Butler, Sara, Billings, Sharon A., Benner, Ronald, Edwards, Kate A., and Ziegler, Susan E. Biochemical and structural controls on the decomposition dynamics of boreal upland forest moss tissues. United States: N. p., 2018. Web. doi:10.5194/bg-15-6731-2018.
Philben, Michael, Butler, Sara, Billings, Sharon A., Benner, Ronald, Edwards, Kate A., & Ziegler, Susan E. Biochemical and structural controls on the decomposition dynamics of boreal upland forest moss tissues. United States. doi:10.5194/bg-15-6731-2018.
Philben, Michael, Butler, Sara, Billings, Sharon A., Benner, Ronald, Edwards, Kate A., and Ziegler, Susan E. Mon . "Biochemical and structural controls on the decomposition dynamics of boreal upland forest moss tissues". United States. doi:10.5194/bg-15-6731-2018. https://www.osti.gov/servlets/purl/1506777.
@article{osti_1506777,
title = {Biochemical and structural controls on the decomposition dynamics of boreal upland forest moss tissues},
author = {Philben, Michael and Butler, Sara and Billings, Sharon A. and Benner, Ronald and Edwards, Kate A. and Ziegler, Susan E.},
abstractNote = {Mosses contribute an average of 20 % of boreal upland forest net primary productivity and are frequently observed to degrade slowly compared to vascular plants. If this is caused primarily by the chemical complexity of their tissues, moss decomposition could exhibit high temperature sensitivity (measured as Q10) due to high activation energy, which would imply that soil organic carbon (SOC) stocks derived from moss remains are especially vulnerable to decomposition with warming. Alternatively, the physical structure of the moss cell-wall biochemical matrix could inhibit decomposition, resulting in low decay rates and low temperature sensitivity. We tested these hypotheses by incubating mosses collected from two boreal forests in Newfoundland, Canada, for 959 days at 5°C and 18°C, while monitoring changes in the moss tissue composition using total hydrolyzable amino acid (THAA) analysis and 13C nuclear magnetic resonance (NMR) spectroscopy. Less than 40 % of C was respired in all incubations, revealing a large pool of apparently recalcitrant C. The decay rate of the labile fraction increased in the warmer treatment, but the total amount of C loss increased only slightly, resulting in low Q10 values (1.23–1.33) compared to L horizon soils collected from the same forests. NMR spectra were dominated by O-alkyl C throughout the experiment, indicating the persistence of potentially labile C. The accumulation of hydroxyproline (derived primarily from plant cell-wall proteins) and aromatic C indicates the selective preservation of biochemicals associated with the moss cell wall. This was supported by scanning electron microscope (SEM) images of the moss tissues, which revealed few changes in the physical structure of the cell wall after incubation. This suggests that the moss cell-wall matrix protected labile C from microbial decomposition, accounting for the low temperature sensitivity of moss decomposition despite low decay rates. Climate drivers of moss biomass and productivity, therefore, represent a potentially important regulator of boreal forest SOC responses to climate change that needs to be assessed to improve our understanding of carbon–climate feedbacks.},
doi = {10.5194/bg-15-6731-2018},
journal = {Biogeosciences (Online)},
number = 21,
volume = 15,
place = {United States},
year = {2018},
month = {1}
}

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