Deep roots of Carex aquatilis have greater ammonium uptake capacity than shallow roots in peatlands following permafrost thaw

• Published in: Plant and soil 2021-08, Vol.465 (1-2), p.261-272
• Main Authors: Albano, Lucas J., Turetsky, Merritt R., Mack, Michelle C., Kane, Evan S.
• Format: Article
• Language: English
• Subjects: Agriculture; Ammonium; Ammonium compounds; Ammonium paratungstate; Anoxic conditions; Biomass; Biomedical and Life Sciences; Bogs; Carex aquatilis; Chemical properties; Climate change; Comparative analysis; Cyperaceae; Discovery and exploration; Ecology; Environmental aspects; Flowers & plants; Frozen ground; Global warming; Identification and classification; Life Sciences; Nitrogen; Nutrient uptake; Nutrients; Observations; Organic matter; Peat-bogs; Peatlands; Permafrost; Physiological aspects; Plant biomass; Plant Physiology; Plant Sciences; Plants; Regular Article; Rooting; Roots; Roots (Botany); Soil nutrients; Soil Science & Conservation; Soils; Structure; Thawing
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-021-04978-x

Aims Climate warming in northern ecosystems is triggering widespread permafrost thaw, during which deep soil nutrients, such as nitrogen, could become available for biological uptake. Permafrost thaw shift frozen organic matter to a saturated state, which could impede nutrient uptake. We assessed whether soil nitrogen can be accessed by the deep roots of vascular plants in thermokarst bogs, potentially allowing for increases in primary productivity. Methods We conducted an ammonium uptake experiment on Carex aquatilis Wahlenb. roots excavated from thermokarst bogs in interior Alaska. Ammonium uptake capacity was compared between deep and shallow roots. We also quantified differences in root ammonium uptake capacity and plant size characteristics (plant aboveground and belowground biomass, maximum shoot height, and maximum root length) between the actively-thawing margin and the centre of each thermokarst bog as a proxy for time-following-thaw. Results Deep roots had greater ammonium uptake capacity than shallow roots, while rooting depth, but not belowground biomass, was positively correlated with aboveground biomass. Although there were no differences in aboveground biomass between the margin and centre, our findings suggest that plants can benefit from investing in the acquisition of resources near the vertical thaw front. Conclusions Our results suggest that deep roots of C. aquatilis can contribute to plant nitrogen uptake and are therefore able to tolerate anoxic conditions in saturated thermokarst bogs. This work furthers our understanding of how subarctic and wetland plants respond to warming and how enhanced plant biomass production might help offset ecosystem carbon release with future permafrost thaw.