Spiraling Down Hillslopes: Nutrient Uptake from Water Tracks in a Warming Arctic
- PDF / 5,586,490 Bytes
- 15 Pages / 593.972 x 792 pts Page_size
- 25 Downloads / 147 Views
Spiraling Down Hillslopes: Nutrient Uptake from Water Tracks in a Warming Arctic Tamara K. Harms,1* Christopher L. Cook,2 Adam N. Wlostowski,3 Michael N. Gooseff,3 and Sarah E. Godsey4 1 Department of Biology and Wildlife, Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska 99775, USA; Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan 48109, USA; 3Department of Civil Architectural and Environmental Engineering, Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado 80309, USA; 4Department of Geosciences, Idaho State University, Pocatello, Idaho 83209, USA
2
ABSTRACT Hydrologic flowpaths might propagate biogeochemical signals among connected ecosystems or alter and dampen signals because of reactions or retention occurring during transport. In the Arctic, experimentally warmed terrestrial tundra releases inorganic nitrogen (N), but the fate of this newly released N remains unclear. Nitrogen could be passively transported downslope in flowing water, or retained when flowpaths intercept N-limited ecosystems. We applied nutrient spiraling theory to simultaneously measure reaction and transport of ammonium (NH4+) and phosphate (PO43-), nutrients limiting primary productivity in Arctic ecosystems. Pulse fertilization experiments were focused on flowpaths known as water tracks that hydrologically connect soils to receiving streams and lakes in upland tundra of Alaska. Water tracks typically retained PO43-, but passively transported NH4+, thus potentially propagating NH4+ produced by warming tundra soils to downstream
ecosystems. Nutrient uptake was uncorrelated with the relative proportion of downslope transport in transient storage zones, but greater NH4+ uptake occurred as advective hydrologic flux increased relative to dispersion. Phosphate uptake declined as thaw depth increased over the summer season likely because of declining capacity for biotic uptake or sorption in deeper soils. Phosphorus limitation in fluvial ecosystems of the Arctic might result in efficient transport of inorganic N to N-limited lentic and coastal ecosystems, where increasing subsidies furnished by N loss from warming terrestrial tundra could support enhanced primary production. Key words: active layer; advection; ammonium (NH4+); flowpaths; mineralization; phosphate (PO43-); saturated soils; transient storage; transport; tundra.
HIGHLIGHTS Received 12 September 2018; accepted 24 January 2019 Electronic supplementary material: The online version of this article (https://doi.org/10.1007/s10021-019-00355-z) contains supplementary material, which is available to authorized users. Authors’ Contributions TKH and SEG designed the study. TKH and CLC collected and analyzed data. ANW and MNG contributed methods and analyzed data. TKH wrote the paper with input from all authors. *Corresponding author; e-mail: [email protected]
Arctic hillslope flowpaths retain phosphorus and transport ammonium. Transient storage dominated downslope flow at low disch
Data Loading...
