Sphagnum Research at the SPRUCE Experiment Site
Spruce and Peatland Responses Under Changing Environments (SPRUCE) is an experiment to assess the response of a northern peatland ecosystem to increases in temperature and elevated atmospheric CO2. Sponsored by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research and the United States Department of Agriculture Forest Service, the experiment is a primary component of the Terrestrial Ecosystem Science Scientific Focus Area of the Climate Change Program at the Oak Ridge National Laboratory. The experiment is fully described in the project’s website (mnspruce.ornl.gov) and in Hanson et al. (2020).
Sphagnum is critical part of this bog ecosystem, and its responses to the experimental manipulations will play a central role in the overall ecosystem response. Sphagnum moss is a keystone component of boreal peatlands and is considered to be an “ecosystem engineer” that creates its own favorable conditions while forming adverse conditions for competing vascular plants. Alteration of any of those conditions brought on by atmospheric and climatic change can be expected to alter growth, vitality, or composition of the Sphagnum community with feedbacks to the functioning of the bog ecosystem.
Our research objective was to determine the responses of growth, productivity, and community composition of the Sphagnum community in response to warming and elevated CO2. Typical of bogs in northern Minnesota with an open tree cover, there is a nearly continuous cover of mosses, primarily Sphagnum angustifolium, S. fallax, and S. magellanicum.
To monitor changes in the species composition of the bryophyte community, we established three transects within each plot and estimated the percentage coverage by S. angustifolium/fallax, S. magellanicum, Polytrichum strictum, Pleurozium schreberi, or (rarely) other Sphagnum species or lichen. We developed a new method for measuring annual growth of Sphagnum, and we calculated plot-level productivity by combining data on dry matter increment and fractional cover.
Key results:
- After three years of warming, annual Sphagnum productivity declined linearly with increasing temperature due to wide–spread desiccation and loss of Sphagnum.
- Productivity was less in elevated CO2 enclosures, which we associate with increased from shading by shrubs.
- Sphagnum desiccation and growth responses were associated with the effects of warming on hydrology.
Net primary productivity (NPP) combines the observations of Sphagnum growth and cover. The response surface indicates a loss 29 g C m-2 per °C warming in ambient CO2 and 13 g C m-2 per °C in elevated CO2, which are significant fractions of the carbon economy of this ecosystem.
Publications on Sphagnum responses (all SPRUCE publications are here)
Primary report of Sphagnum responses to warming and elevated CO2:
Norby RJ, Childs J, Hanson PJ, Warren JM. 2019. Rapid loss of an ecosystem engineer: Sphagnum decline in an experimentally warmed bog. Ecology and Evolution 9:12571-12585. DOI: 10.1002/ece3.5722. PDF
Sphagnum response data file
Norby RJ, Childs J. 2018. SPRUCE: Sphagnum productivity and community composition in the SPRUCE experimental plots. Oak Ridge National Laboratory, TES SFA, U.S. Department of Energy, Oak Ridge, TN. USA. DOI: 10.25581/spruce.049/1426474
Whole ecosystem carbon fluxes, including the role of Sphagnum:
Hanson PJ, Griffiths NA, Iversen CM, Norby RJ, Sebestyen SD, Phillips JR, Chanton JP, Kolka RK, Malhotra A, Oleheiser KC, Warren JM, Shi X, Yang X, Mao J, Ricciuto DM. 2020. Rapid net carbon loss from a whole-ecosystem warmed peatland. AGU Advances AGA220032, DOI: 10.1029/2020AV000163. PDF
Pretreatment carbon budget, including Sphagnum
Griffiths NA, Hanson PJ, Ricciuto DM, Iversen CM, Jensen AM, Malhotra A, McFarlane KJ, Norby RJ, Sargsyan K, Sebestyen SB, Shi X, Walker AP, Ward EJ, Warren JM, Weston DJ. 2017. Temporal and spatial variation in peatland carbon cycling and implications for interpreting responses of an ecosystem-scale warming experiment. Soil Science Society of America Journal 81: 1668-1688. DOI:10.2136/sssaj2016.12.0422. PDF
Model development
Shi X, Ricciuto DM, Thornton PE, Xu X, Yuan F, Norby RJ, Walker AP, Warren J, Mao J, Hanson PJ, Meng L, Weston D, Griffiths NA. 2021. Extending a land-surface model with Sphagnum moss to simulate responses of a northern temperate bog to whole ecosystem warming and elevated CO2. Biogeosciences, DOI: 10.5194/bg-18-467-2021. PDF
Model analysis of Sphagnum productivity
Walker AP, Carter KR, Gu LH, Hanson PJ, Malhotra A, Norby RJ, Sebestyen SD, Wullschleger SD, Weston DJ. 2017. Biophysical drivers of seasonal variability in Sphagnum gross primary production in a northern temperate bog. Journal of Geophysical Research‐Biogeosciences, 122:, 1078– 1097. DOI: 10.1002/2016jg003711. PDF
The Sphagnome project
Weston DJ, Turetsky MR, Johnson MG, Granath G, Lindo Z, Belyea LR, Rice SK, Hanson DT, Engelhardt KAM, Schmutz J, Dorrepaal E, Euskirchen ES, Stenøien HK, Szövényi P, Jackson M, Piatkowski BT, Muchero W, Norby RJ, Kostka JE, Glass JB, Rydin H, Limpens J, Tuittila E-S, Ullrich KK, Carrell A, Benscoter BW, Chen J-G, Oke TA, Nilsson MB, Ranjan P, Jacobson D, Lilleskov EA, Clymo RS, Shaw AJ. 2018. The Sphagnome Project: enabling ecological and evolutionary insights through a genus-level sequencing project. New Phytologist 217: 16-25, DOI:10.1111/nph.14860. PDF
Sphagnum as a model species
Weston DJ, Timm CM, Walker AP, Gu L, Muchero W, Schmutz J, Shaw AJ, Tuskan GA, Warren JM, Wullschleger SD. 2015. Sphagnum physiology in the context of changing climate: emergent influences of genomics, modelling and host–microbiome interactions on understanding ecosystem function. Plant, Cell & Environment 38: 1737-1751.DOI: 10.1111/pce.12458. PDF
See more about Dave Weston’s work with Sphagnum here
Sphagnum is a very cool organism!
Measurements of growth and community composition
Richard J. Norby 