December 16, 2020

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Shrub-Layer Diversity Is Reduced Yet Overall Productivity Increased with Climate Warming

Experimental treatments at DOE’s SPRUCE warming study in northern Minnesota show cumulative changes in peatland shrub-layer vegetation.

Declining diversity indices (left) and increase overall annual productivity (right) characterize the cumulative impact of 4 years of sustained warming treatments.
[Image Credit: Figures from McPartland et al. 2020.]

The Science

Peatlands store a significant amount of terrestrial organic carbon in plant biomass and soils. The Spruce and Peatland Responses Under Changing Environments (SPRUCE) project is a warming and elevated carbon dioxide (eCO2) experiment designed to test how the carbon sequestration and storage capacity of peatland ecosystems will respond to climate change. Here, the researchers report changes in the vascular plant community that have occurred during the first five years of SPRUCE. The team tracked species composition, diversity, and aboveground net primary production in chambers warmed at a wide range of temperatures (+0, +2.25, +4.5, +6.75, +9°C), and two CO2 levels (~400 [ambient] and 900 parts per million) related to near- and long-term climate possibilities.

The Impact

The researchers observed an increase in aboveground vascular plant biomass accumulation, due primarily to an increase in shrub abundance. Overall species diversity decreased substantially, likely due in part to shading by increases in shrub density. The main driver of change in the vascular plant community was temperature, with minimal effects of CO2 evident. Dominant growth increases of woody shrubs hid similarly dramatic reductions in common and overtopped forb vegetation.


Project results indicate an overall increase in shrub-layer vegetation suggesting that warmer future climates could enhance productivity of woody peatland vegetation, but at a cost to the diversity comprising that community. Such data are an essential component of carbon cycle models of wetland ecosystems key to the global assessment of terrestrial carbon cycles.

Principal Investigator

Paul Hanson
Oak Ridge National Laboratory

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science


The Spruce and Peatland Responses Under Changing Environments experiment is supported by the Office of Biological and Environmental Research within the U.S. Department of Energy (DOE) Office of Science. This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with DOE.

Related Links


McPartland, M. Y., R. A. Montgomery, P. J. Hanson, and J. R. Phillips, et al. "Vascular plant species response to warming and elevated carbon dioxide in a boreal peatland". Environmental Research Letters 15 124066  (2020).

McPartland, M. Y., M. J. Falkowski, R. Kolka, and M. R. Turetsky, et al. SPRUCE: Vegetation community survey data from SPRUCE experimental plots, 2014-2018. 2019. Oak Ridge National Laboratory, TES SFA, U.S. Department of Energy, Oak Ridge, Tennessee, U.S.A.

Hanson, P. J., J. R. Phillips, D. J. Brice, and L. A. Hook. SPRUCE shrub-layer growth assessments in S1-bog plots and SPRUCE experimental plots beginning in 2010. 2018. Oak Ridge National Laboratory, TES SFA, U.S. Department of Energy, Oak Ridge, Tennessee, U.S.A.