Peatland warming strongly increases fine-root growth

Belowground climate change responses 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 carbon cycling. However, fine-root re...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2020-07, Vol.117 (30), p.17627-17634
Main Authors: Malhotra, Avni, Brice, Deanne J., Childs, Joanne, Graham, Jake D., Hobbie, Erik A., Vander Stel, Holly, Feron, Sarah C., Hanson, Paul J., Iversen, Colleen M.
Format: Article
Language:English
Subjects:
belowground plant response
Biological Sciences
Carbon
Carbon cycle
Carbon sinks
Climate change
Drying
elevated carbon dioxide
Environmental changes
ENVIRONMENTAL SCIENCES
experimental warming
fine roots
Nutrient cycles
Nutrient uptake
peatland
Peatlands
Physical Sciences
Shrubs
Soil moisture
Soil temperature
Soils
Vegetation
Water uptake
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Summary:Belowground climate change responses 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 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. We present fine-root responses to warming between +2 °C and 9 °C above ambient conditions in a whole-ecosystem peatland experiment. Warming strongly increased fine-root growth by over an order of magnitude in the warmest treatment, with stronger responses in shrubs than in trees or graminoids. In the first year of treatment, the control (+0 °C) shrub fine-root growth of 0.9 km m−2 y−1 increased linearly by 1.2 km m−2 y−1 (130%) for every degree increase in soil temperature. An extended belowground growing season accounted for 20% of this dramatic increase. In the second growing season of treatment, the shrub warming response rate increased to 2.54 km m−2 °C−1. 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 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 composition, and ultimately, carbon function of these globally relevant carbon sinks.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.2003361117