Alex Webster led analyses of high-frequency data from headwater catchments draining varying spatial extents of permafrost. Compared to low/no permafrost catchments, higher-permafrost catchments showed season-long trends in nitrate concentration, a step-change in solute concentrations initiated by late-season precipitation, counter-clockwise concentration-discharge hysteresis during storms, and shifts in the phase of concentration-discharge coherence at the timescale of storms. Ecosystems
Long-term Ecological Research Network: organic matter synthesis /
We synthesized organic matter dynamics across terrestrial, freshwater, and marine ecosystems in the Long-Term Ecological Research Network (Climate Change Ecology). The synthesis highlights effects of climate change and coupling with nutrient cycles on organic matter storage. We identified opportunities for enhancing understanding and predicting organic matter dynamics by studying effects of transport in terrestrial ecosystems, incorporating analyses of organic matter composition, and analysis of temporal patterns in long-term data.
Greenhouse gas emissions from Arctic hillslopes /
We report emissions of CO2, CH4, and N2O from Arctic water tracks in a new paper out in JGR-Biogeosciences. Water tracks, aquatic features that drain hillslope soils, emit CO2 and CH4 at rates among the highest of high-latitude aquatic ecosystems. Emissions from water tracks partially offset the carbon sink of terrestrial tundra.
The Lab & Collaborators at AGU /
H13Q-1994 Quantifying hydrologic regime shifts on ecological time scales using wavelets
John L Sabo (Arizona State University), Tamara Harms (University of Alaska Fairbanks), Albert Ruhi (UC Berkeley)
Monday afternoon posters
B23H-2517 Denitrification and Nitrous Oxide Production in Boreal Terrestrial and Aquatic Ecosystems Varying in Permafrost and Fire Disturbance History
Melanie Burnett (University of Alaska Fairbanks), Tamara Harms (University of Alaska Fairbanks)
Tuesday afternoon posters
B23I-2536 Detecting catchment-scale permafrost degradation and biogeochemical regime change from high-frequency stream chemistry
Alex Webster (University of Alaska Fairbanks), Thomas Douglas (Cold Regions Research and Engineering Laboratory Alaska), Peter Regier (University of New Mexico), Tamara Harms (University of Alaska Fairbanks)
Tuesday afternoon posters
B23H-2518 Stream Chemistry Indicates Catchment Response to Disturbance and Regional Warming in the Boreal Forest
Adela Contreras (University of California, Davis), Alex Webster (University of Alaska Fairbanks), Rachel L. Willis (University of Alaska Fairbanks), Tamara Harms (University of Alaska Fairbanks)
Tuesday afternoon posters
B53D-05 Flow variation and the biogeochemistry of desert streams
Tamara Harms (University of Alaska Fairbanks), John L Sabo (Arizona State University)
Friday 14:40-14:55, Moscone West 3001
Ph.D. student position in ecosystem resilience /
We are recruiting a Ph.D. student to join our project on resilience of boreal ecosystems to fire and permafrost thaw. The team is investigating whether catchment biogeochemical signals, measured using instream sensors, provide early warning of ecosystem regime change. Interested students can contact Dr. Harms describing their interests and experience. The position begins summer 2020.
Climate effects on discharge and nitrogen flux in the Mississippi River basin /
Time series analysis showed differential effects of the North Atlantic Oscillation and El Niño Southern Oscillation on river discharge and nitrogen flux in the Mississippi-Atchafalaya River Basin. Modeling effort led by Adrianne Smits, with collaboration from the Stream Resilience Research Coordination Network. https://doi.org/10.1029/2018GL081166
Nitrogen & phosphorus uptake from water tracks on arctic hillslopes /
Water tracks, the zero-order channels that drain arctic hillslopes, retain phosphate, but export ammonium. doi.org/10.1007/s10021-019-00355-z
Song et al. on stream metabolism /
New paper synthesizing stream metabolism from our SCALER project shows that potential increase in CO2 emission from streams is related to temperature and metabolic balance. doi:10.1038/s41561-018-0125-5