Nutrient and water flux in a small arctic watershed: an overview

Abstract

The “Response, Resistance, Resilience to, and Recovery from Disturbance in Arctic Ecosystems” (R4D) program initially concentrated on impacts of altered water and nutrient inputs on tussock tundra vegetation. The intensive site is at Imnavait Creek (68°C 37′ N, 149° 17′ E), near Toolik Lake. Alaska in the foothills of the Brooks Range, approximately 200 km south of Prudhoe Bay. Tussock tundra was selected for initial study because it has an extensive distribution in the Alaskan Arctic (80% of the arctic region), the majority of the pipeline corridor north of the Brooks Range passes through tussock tundra, and disturbances of arctic tundra are expected to occur in the future. Also important is that 18% of the circumpolar arctic primary productivity and 47% of the circumpolar arctic stored carbon are in tussock tundra.Water and nutrient additions were performed because they frequently accompany disturbance and development in the Arctic. Emphasis was placed on determining responses of physical, physiological, and ecosystem processes to environmental change in such a way that extrapolations to other areas would be facilitated. The hills near Imnavait Creek are covered by glacial till of the Sagavanirktok River glaciation. with a deep organic layer on the less exposed hill slopes and valleys. The vegetation is dominated by Eriophorum vaginatum L., Betula nana L., Vaccirtium uliginosum L, Vaccinium viiis‐idaea L., Ledum palustre L., Salix pulcbra L., and Sphagnum spp. Winds were rarely calm but seldom exceed 17 m s−1, generally from the east‐southeast to the south‐southwest (66%). Precipitation in 1986 was 344 mm, about half of which was snowfall. Mean temperature in 1986 was −8.1°C, with an absolute minimum of −43°C. Mean July temperature was between 9.8 and 13.7°C. Nutrients are more mobile than previously thought, moving an estimated 10 m downslope in the first growing season. It underscores the importance of the winter environment to biological and hydrological processes. Greater water flow results in increased plant growth rates, leaf area, and biomass.Effects of changes in nutrient and water supply on photosynthesis were minimal. Where increases in productivity took place, they occurred more likely as a result of changes in allocation patterns, including an initial redirection of carbohydrate stores to new leaf development, than from increases in photosynthetic rates.The work reported here indicates that the downslope transmission of nutrient and water flow effects caused by altered drainage and nutrient supply may result in a larger area of impact than previously thought.