July 28, 2020
Hidden Plant Responses to Environmental Change
Fine-root growth increases dramatically in an experimentally warmed peatland.
Peatlands store a significant amount of global soil carbon and are vulnerable to global change. The warming response of peatland plants is expected to influence future carbon uptake and storage but is poorly understood, especially belowground. Researchers at the Spruce and Peatland Responses Under Changing Environments (SPRUCE) whole-ecosystem warming experiment found warming (and soil drying) significantly increases fine-root growth. The magnitude of this belowground response is 20× higher than previously observed in similar experiments from upland ecosystems.
Increases in shrub abundance, or ‘shrubification’, of northern peatlands under warmer conditions has been seen aboveground in previous studies. However, this work highlights belowground mechanisms that enable shrubs to rapidly adapt to warmer and drier conditions. Fine-root data and responses from this study will also enable improved representation of peatlands into Earth system models.
Belowground responses to climate change remain a key unknown in the Earth system. Plant fine-root response is especially important to understand because fine roots respond quickly to environmental change, are responsible for nutrient and water uptake, and influence ecosystem carbon cycling. However, fine-root responses to climate change are poorly constrained, especially in northern peatlands, which contain up to two-thirds of the world’s soil carbon. Using a whole-ecosystem warming manipulation, researchers at SPRUCE found that warming strongly increased ecosystem fine-root growth. Shrub fine-root production increased linearly by 1.2 km m-2 year-1 for every degree increase in soil temperature. Soil moisture was negatively correlated with fine-root growth, highlighting that drying of these typically water-saturated ecosystems can fuel a surprising burst in shrub belowground productivity; one possible mechanism explaining the ‘shrubification’ of northern peatlands in response to global change. This previously unrecognized belowground mechanism sheds light on how peatland fine-root response to warming and drying could be strong and rapid, with consequences for the belowground growing season duration, microtopography, vegetation community structure and ultimately, carbon function of these globally relevant carbon sinks.
Oak Ridge National Laboratory
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
The Spruce and Peatland Responses Under Changing Environments (SPRUCE) experiment is supported by the Office of Biological and Environmental Research in the United States Department of Energy’s Office of Science.
Malhotra A., D. Brice, J. Childs, and J. D. Graham, et al. "Peatland warming strongly increases fine-root growth". Proceedings of the National Academy of Sciences USA 117 (30), 17627–17634 (2020). https://doi.org/10.1073/pnas.2003361117.