Nutrient Addition Prompts Rapid Destabilization of Organic Matter in an Arctic Tundra Ecosystem

• Published in: Ecosystems (New York) Vol. 11; no. 1; pp. 16 - 25
• Main Authors: Nowinski, Nicole S., Trumbore, Susan E., Schuur, Edward A. G., Mack, Michelle C., Shaver, Gaius R.
• Format: Journal Article
• Language: English
• Published: New York Springer Science+Business Media 01-02-2008; Springer-Verlag; Springer; Springer Nature B.V
• Subjects: Acid soils; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Biomedical and Life Sciences; Decomposition; Ecology; Ecosystems; Environmental Management; Fertilization; Fundamental and applied biological sciences. Psychology; General aspects; Geochemistry; Geoecology/Natural Processes; Hydrology/Water Resources; Life Sciences; Litter; Marine ecosystems; Mineral soils; Nitrogen; Nutrient availability; Nutrient loss; Nutrients; Organic matter; Organic soils; Phosphorus; Plant Sciences; Plants; Radiocarbon; Soil ecology; Soil horizons; Soil organic matter; Synecology; Taiga & tundra; Tundra; Vertical distribution; Zoology; Arctic Region; tundra; radiocarbon; decomposition; carbon dynamics; nitrogen; phosphorus; Organic matter; Dynamics; Ecosystem; Nutrient; Phosphorus; Decomposition; Nitrogen; Damage; Carbon; Tundra
• ISSN: 1432-9840; 1435-0629
• DOI: 10.1007/S10021-007-9104-1

Nutrient availability in the arctic is expected to increase in the next century due to accelerated decomposition associated with warming and, to a lesser extent, increased nitrogen deposition. To explore how changes in nutrient availability affect ecosystem carbon (C) cycling, we used radiocarbon to quantify changes in belowground C dynamics associated with long-term fertilization of graminoid-dominated tussock tundra at Toolik Lake, Alaska. Since 1981, yearly fertilization with nitrogen (N) and phosphorus (P) has resulted in a shift to shrub-dominated vegetation. These combined changes have altered the quantity and quality of litter inputs, the vertical distribution and dynamics of fine roots, and the decomposition rate of soil organic C. The loss of C from the deep organic and mineral soil has more than offset the C accumulation in the litter and upper organic soil horizons. In the litter and upper organic horizons, radiocarbon measurements show that increased inputs resulted in overall C accumulation, despite being offset by increased decomposition in some soil pools. To reconcile radiocarbon observations in the deeper organic and mineral soil layers, where most of the ecosystem C loss occurred, both a decrease in input of new root material and a dramatic increase of decomposition rates in centuries-old soil C pools were required. Therefore, with future increases in nutrient availability, we may expect substantial losses of C which took centuries to accumulate.