U.S. Department of Energy Office of Biological and Environmental Research

PI-Submitted Research Highlights for
Terrestrial Ecosystem Science Program

Fine-Root Growth in a Forested Bog is Seasonally Dynamic, But Shallowly Distributed in Nutrient-Poor Peat Environments

Colleen M. Iversen
Oak Ridge National Laboratory

Highlight

12 June 2017

Characterizing pre-treatment rooting distribution and dynamics at the site of the SPRUCE experiment.

The Science
As one of the few studies to adapt minirhizotron technology for use in waterlogged peatlands, we were able to provide a rare glimpse into the hidden patterns of root distribution and dynamics in a forested, ombrotrophic bog.

The Impact
Fine roots contribute to ecosystem biogeochemical cycles through resource acquisition and respiration, as well as their death and decay, but are understudied in peatlands. Changes in the distribution of roots throughout the peat profile, across the landscape, and over time could alter the delicate balance of peat accumulation.

Summary
In this fundamental study, we aimed to determine how the amount and timing of fine-root growth in a forested, ombrotrophic bog varied across gradients of vegetation density, peat microtopography, and changes in environmental conditions across the growing season and throughout the peat profile. We quantified fine-root peak standing crop and growth using non-destructive minirhizotron technology over a two-year period, focusing on the dominant woody species in the bog. We found that fine-root standing crop and growth varied spatially across the bog in relation to tree density and microtopography, and we observed tradeoffs in root growth in relation to aboveground woody growth rather than environmental variables such as peat temperature and light. A shallow water table level constrained living fine roots to the aerobic zone, which is extremely poor in plant-available nutrients, and ancient, undecomposed, fine roots in peat below the water table suggest a significant contribution of roots to historical accumulated peat. We expect the controls over the distribution and dynamics of fine roots in this bog to be sensitive to projected warming and drying in northern peatlands.

Contacts (BER PM)
Daniel Stover
SC-23.1
Daniel.Stover@science.doe.gov (301-903-0289)

(PI Contact)
Colleen M. Iversen
Senior Staff Scientist
Environmental Sciences Division and
Climate Change Science Institute
Oak Ridge National Laboratory
iversencm@ornl.gov
(865) 214-3961

Funding
Department of Energy, Office of Science, Biological and Environmental Research Program.  

Publications
Iversen CM, Childs J, Norby RJ, Ontl TA, Kolka RK, Brice DJ, McFarlane KJ, Hanson PJ. 2017. Fine-root growth in a forested bog is seasonally dynamic, but shallowly distributed in nutrient-poor peat. Plant and Soil, DOI: 10.1007/s11104-017-3231-z.

Related Links
Data products:
Iversen CM, Childs J, Norby RJ, Garrett A, Martin A, Spence J, Ontl TA, Burnham A, Latimer J, 2017. SPRUCE S1 bog fine-root production and standing crop assessed with minirhizotrons in the Southern and Northern ends of the S1 bog. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee, U.S.A. http://dx.doi.org/10.3334/CDIAC/spruce.019.

Iversen CM, Garrett A, Martin A, Turetsky MR, Norby RJ, Childs J, Ontl TA. 2017. SPRUCE S1 bog tree basal area and understory community composition assessed in the Southern and Northern ends of the S1 bog. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee, U.S.A. http://dx.doi.org/10.3334/CDIAC/spruce.024.

Iversen CM, Ontl TA, Brice DJ, Childs J. 2017. SPRUCE S1 Bog plant-available nutrients assessed with ion-exchange resins from 2011-2012 in the Southern end of the S1 bog. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee, U.S.A. http://dx.doi.org/10.3334/CDIAC/spruce.022.

Iversen CM, Latimer J, Burnham A, Brice DJ, Childs J, Vander Stel HM. 2017. SPRUCE plant-available nutrients assessed with ion-exchange resins in experimental plots, beginning in 2013. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee, U.S.A. http://dx.doi.org/10.3334/CDIAC/spruce.036.

Ontl TA, Iversen CM. 2017. SPRUCE S1 bog areal coverage of hummock and hollow microtopography assessed along three transects in the S1 bog. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee, U.S.A. http://dx.doi.org/10.3334/CDIAC/spruce.023.

Oak Ridge National Laboratory Terrestrial Ecosystem Sciences Science Focus Area

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