June 12, 2017

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

Characterizing pretreatment 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, this project was 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, scientists 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. they quantified fine-root peak standing crop and growth using nondestructive minirhizotron technology over a two-year period, focusing on the dominant woody species in the bog. They found that fine-root standing crop and growth varied spatially across the bog in relation to tree density and microtopography, and they 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. The team 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.

Principal Investigator

Colleen Iversen
Oak Ridge National Laboratory
iversencm@ornl.gov

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
daniel.stover@science.doe.gov

Funding

Office of Biological and Environmental Research, within the U.S. Department of Energy Office of Science.

References

Iversen, C. M., J. Childs, R. J. Norby, and T. A. Ontl, et al. "Fine-root growth in a forested bog is seasonally dynamic, but shallowly distributed in nutrient-poor peat." Plant and Soil 424 123–143 (2018). https://doi.org/10.1007/s11104-017-3231-z.