Peatland plants hide responses to environmental change

Fine roots grow dramatically faster in an experimentally warmed peatland

DOE/US DEPARTMENT OF ENERGY

image: Shrub fine-roots, often finer than human hair, tangled around a Sphagnum moss stem. The fate of these seemingly tiny plant components is closely tied to carbon cycling of peatlands, which are important to the planet as carbon sinks. view more 

Credit: Photo credit: Colleen Iversen, Oak Ridge National Laboratory

The Science

Lands covered in peat, a mix of partially decayed organic material, store a significant amount of carbon. These peatlands are vulnerable to global changes in temperature. Researchers expect the response of plants in peatlands to warming climates to influence future carbon uptake and storage. However, researchers do not fully understand this mechanism, especially below ground level. Researchers at the Spruce and Peatland Responses Under Changing Environments (SPRUCE) whole-ecosystem warming experiment studied processes below ground. They found that warming and the resulting soil drying, significantly increased the growth of fine roots. The magnitude of this belowground response is 20 times greater than previously observed in similar experiments from upland ecosystems.

The Impact

Previous studies have found increases in the abundance of shrub, or “shrubification,” in northern peatlands under warmer conditions. This new work highlights belowground mechanisms that enable shrubs to rapidly adapt to warmer and drier conditions. Data collected on fine roots will enable researchers to better represent peatlands in Earth system models.

Summary

Belowground responses to climate change are a key unknown in the Earth system. Plants’ 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. Soil moisture negatively correlated with fine-root growth, highlighting how drying of these typically water-saturated ecosystems can fuel a surprising burst in shrub belowground productivity. This is 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.

Funding

The Spruce and Peatland Responses Under Changing Environments (SPRUCE) experiment is supported by the Department of Energy Office of Science, Office of Biological and Environmental Research.

Publications

Malhotra A., et al., Peatland warming strongly increases fine-root growth. PNAS 117 (30) 17627-17634 (2020). [DOI: 10.1073/pnas.2003361117]