September 12, 2019

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Co-Occurring Peat Bog Shrubs at the Boreal-Temperate Ecotone Have Differential Photosynthetic Responses to Warming

Detailed seasonal photosynthetic and respiratory acclimation improve models

The Science

Plant species growing at the southern edge of their ranges must acclimate to warming temperatures if they are to remain competitive. Understanding how different species respond seasonally to new conditions will provide insight into potential shifts in community composition and ecosystem function in the future.

The Impact

Earth system models typically group different species into plant functional types, such as boreal evergreen shrubs. However, this research shows that even species from the same family (Ericaceae) can have very different phenological and physiological responses to changes in environmental conditions. As such, it is important to consider the differential acclimation of individual species in order to improve the performance of model projections.


Researchers measured seasonal patterns of photosynthesis, respiration, and non-structural carbohydrates for two dominant woody evergreen shrubs in a wet boreal forest peatland exposed to whole ecosystem warming and elevated carbon dioxide concentrations. Warming created a longer active season for both species, and there was evidence of thermal acclimation of both photosynthesis and respiration, although this varied seasonally and between species. Chamaedaphne (leatherleaf) photosynthesis increased with temperature under moderate warming but declined above +4 °C, while there was no evidence of this thermal acclimation for Rhododendron (Labrador tea). Overwintered Rhododendron leaf respiration rates decreased with temperature up to +9 °C, while there was no evidence of this thermal acclimation for Chamaedaphne. Under elevated CO2 conditions, both species had large increases in leaf sugars and starch, and this coincided with a reduction in both N content (Chamaedaphne only) and photosynthetic capacity. Species-specific performance and vigor depends on the balance between thermal and CO2 acclimation and how those processes play out over longer-time scales.

Principal Investigator

Jeffery M. Warren
Oak Ridge National Laboratory
[email protected]

Program Manager

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


U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the DOE under contract DE-AC05-1008 00OR22725.


Ward, E. J., et al. "Photosynthetic and Respiratory Responses of Two Bog Shrub Species to Whole Ecosystem Warming and Elevated CO2 at the Boreal-Temperate Ecotone." Frontiers in Forests and Global Change 2 (54), (2019).