Nitrogen uptake during fall, winter and spring differs among plant functional groups in a subarctic heath ecosystem

• Published in: Ecosystems
• Main Authors: Larsen, Klaus Steenberg, Michelsen, Anders, Jonasson, Sven Evert, Beier, Claus, Grogan, Paul
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2012
• Subjects: Subarctic; Tundra
• Online Access: https://curis.ku.dk/portal/da/publications/nitrogen-uptake-during-fall-winter-and-spring-differs-among-plant-functional-groups-in-a-subarctic-heath-ecosystem(1b4aad29-11f3-4435-a35e-d178cd5bb5c0).html; https://doi.org/10.1007/s10021-012-9555-x

Nitrogen (N) is a critical resource for plant growth in tundra ecosystems, and species differences in the timing of N uptake may be an important feature regulating community composition and ecosystem productivity. We added N-15-labelled glycine to a subarctic heath tundra dominated by dwarf shrubs, mosses and graminoids in fall, and investigated its partitioning among ecosystem components at several time points (October, November, April, May, June) through to the following spring/early summer. Soil microbes had acquired 65 +/- A 7% of the N-15 tracer by October, but this pool decreased through winter to 37 +/- A 7% by April indicating significant microbial N turnover prior to spring thaw. Only the evergreen dwarf shrubs showed active N-15 acquisition before early May indicating that they had the highest potential of all functional groups for acquiring nutrients that became available in early spring. The faster-growing deciduous shrubs did not resume N-15 acquisition until after early May indicating that they relied more on nitrogen made available later during the spring/early summer. The graminoids and mosses had no significant increases in N-15 tracer recovery or tissue N-15 tracer concentrations after the first harvest in October. However, the graminoids had the highest root N-15 tracer concentrations of all functional groups in October indicating that they primarily relied on N made available during summer and fall. Our results suggest a temporal differentiation among plant functional groups in the post-winter resumption of N uptake with evergreen dwarf shrubs having the highest potential for early N uptake, followed by deciduous dwarf shrubs and graminoids.