Experimentally increased nutrient availability at the permafrost thaw front selectively enhances biomass production of deep-rooting subarctic peatland species

• Published in: Global Change Biology
• Main Authors: Keuper, Frida, Dorrepaal, Ellen, van Bodegom, Peter M., van Logtestijn, Richard, Venhuizen, Gemma, van Hal, Jurgen, Aerts, Rien
• Other Authors: Agroressources et Impacts environnementaux (AgroImpact), Institut National de la Recherche Agronomique (INRA), Vrije Universiteit Amsterdam Amsterdam (VU), Umeå University, Leiden University, Darwin Centre for Biogeosciences 142.161.042, FP6 506004, EU-ATANS 142.161.042, FP6 506004
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: belowground nitrogen; climate change; Empetrum hermaphroditum; fertilization; frozen soil; permafrost thaw; root uptake; Rubus chamaemorus; [SDV]Life Sciences [q-bio]; [SDV.BV]Life Sciences [q-bio]/Vegetal Biology; [SDE]Environmental Sciences; permafrost; Subarctic
• Online Access: https://hal.inrae.fr/hal-02619005; https://doi.org/10.1111/gcb.13804

International audience Climate warming increases nitrogen (N) mineralization in superficial soil layers (the dominant rooting zone) of subarctic peatlands. Thawing and subsequent mineralization of permafrost increases plant-available N around the thaw-front. Because plant production in these peatlands is N-limited, such changes may substantially affect net primary production and species composition. We aimed to identify the potential impact of increased N-availability due to permafrost thawing on subarctic peatland plant production and species performance, relative to the impact of increased N-availability in superficial organic layers. Therefore, we investigated whether plant roots are present at the thaw-front (45 cm depth) and whether N-uptake (N-15-tracer) at the thaw-front occurs during maximum thaw-depth, coinciding with the end of the growing season. Moreover, we performed a unique 3-year belowground fertilization experiment with fully factorial combinations of deep-(thaw-front) and shallow-fertilization (10 cm depth) and controls. We found that certain species are present with roots at the thaw-front (Rubus chamaemorus) and have the capacity (R. chamaemorus, Eriophorum vaginatum) for N-uptake from the thaw-front between autumn and spring when aboveground tissue is largely senescent. In response to 3-year shallow-belowground fertilization (S) both shallow-(Empetrum hermaphroditum) and deep-rooting species increased aboveground biomass and N-content, but only deep-rooting species responded positively to enhanced nutrient supply at the thaw-front (D). Moreover, the effects of shallow-fertilization and thaw-front fertilization on aboveground biomass production of the deep-rooting species were similar in magnitude (S: 71%; D: 111% increase compared to control) and additive (S + D: 181% increase). Our results show that plant-available N released from thawing permafrost can form a thus far overlooked additional N-source for deep-rooting subarctic plant species and increase their biomass production beyond the ...