Nitrogen Availability Increases in a Tundra Ecosystem During Experimental Permafrost Thaw
Plant access to an essential nutrient increases under warmed conditions.
Researchers warmed a tundra ecosystem in Alaska’s interior for 5 years with a novel experimental method. With this method, the researchers were able to warm the deep soil and degrade the permafrost, as well as document increases in plant access to soil nitrogen, a key nutrient.
Global warming will result in the thaw of perennially frozen soils (permafrost), with releases of carbon to the atmosphere. However, this study’s findings show that increased growth of tundra plants could remove some of this carbon from the atmosphere, thus offsetting, in part, the accelerating feedback to climate change.
Researchers monitored nitrogen in tundra plants and soils during 5 years of experimental warming to quantify how plant access to soil nitrogen changed during permafrost thaw. Nitrogen is a scarce nutrient in high-latitude ecosystems, and plant access to soil nitrogen currently limits plant growth. Within 5 years of warming, plant-available nitrogen in soils increased. Warmed plants were able to grow larger and take up more carbon from the atmosphere than their unwarmed (control) neighbors. Though the study showed that plant biomass increased with warming, it is unlikely that the observed increase in plant carbon storage will be greater than losses of permafrost carbon at this site. In sum, plant carbon uptake offsets, in part, carbon releases from soils, but the system remains a net source of carbon to the atmosphere as a result of permafrost thaw and thus contributes toward accelerating climate change.
Northern Arizona University
This work was supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research, Terrestrial Ecosystem Science program; National Science Foundation CAREER program; National Parks Inventory and Monitoring Program; National Science Foundation Bonanza Creek LTER program; National Science Foundation Office of Polar Programs; and a Discover Denali Research Fellowship awarded to V. Salmon.
Salmon, V. G., et al. “Nitrogen availability increases in a tundra ecosystem during 5 years of experimental permafrost thaw.” Glob. Change Biol. 22(5), 1927–41 (2015). DOI:10.1111/gcb.13204.