1. Will future climate accelerate carbon loss from Arctic soils and cause a positive feedback to future warming?
2. Will shrub expansion accelerate or dampen further Arctic climate warming?
3. Will rapid permafrost melting decrease soil carbon and increase releases of carbon to the atmosphere and nutrients to streams and rivers?
4. How will increased nutrients from land associated with warming alter the structure and functioning of Arctic rivers?

We will spend our mornings collecting samples in the field and our afternoons and evenings analyzing samples and interpreting data. Teams of two participants will have responsibility for analyzing and interpreting data for each question in greater depth. Each team will be responsible for preparing a presentation and leading a discussion on their unit. There will be many interesting linkages between the units, so all participants will have input into these discussions. Teams will receive help analyzing, interpreting and explaining results.

Detailed Schedule of Activities

June 17. Arrival at Fairbanks airport late at night. Transport to University of Alaska dormitories.

June 18. Day in Fairbanks. Introduction to the Institute of Arctic Biology, visit Museum of the North, Large Animal Research Station. Introductory dinner in evening.

June 19. Drive Dalton Highway to Toolik Field Station

June 20. Toolik orientation day. Introduction to Toolik Field Station and Long-Term Ecological Research Projects and research at Toolik. “Talking Shop” session with TFS residents. Be prepared to talk for five minutes about the kind of science journalism you do.

June 21. Field exercise: Carbon balance of tundra ecosystems
Question. Will future climate accelerate carbon loss from Arctic soils?
Issue. Arctic soils store more carbon than soils of any other biome on earth. Almost all of this carbon is stored as organic matter (peat) that has accumulated because the cold and wet environment of Arctic soils retards decomposition and promotes carbon storage. However, the climate of polar regions is warming faster than anywhere else on earth. If warmer temperatures cause Arctic soils to dry out, accelerated decomposition will release CO2 that could cause a runaway feedback that will result in further warming, more CO2 release and accelerate future warming. How the great stores of carbon in Arctic soils will respond to climate change is a subject of active research in the tundra around Toolik.

Activities. Ecosystem carbon balance depends on the relative magnitudes of carbon fixation by photosynthesis (carried out by plants in the light) and respiration (carried out by plants, animals and bacteria 24 hours a day). We will measure ecosystem carbon balance (net ecosystem production) by enclosing tundra in a clear chamber and measuring carbon uptake in the natural light and then at several reduced light levels. We will use records of light levels recorded at Toolik to model carbon balance over days and growing seasons.

We will measure net ecosystem production in plots of tussock tundra that have been treated in three different ways since 1988 as part of an Arctic LTER project run by Gus Shaver. The treatments are: 1) control (natural tundra), and 2) tundra fertilized with nitrogen and phosphorus each year. Over the years, these treatments have altered the tundra vegetation. We will compare net ecosystem production in the three long-term treatments. We will then discuss what these treatments tell us about how net ecosystem production and soil carbon stocks will change in a future Arctic.

Key readings (click links for pdf file)
Mack, M. C., E. A. G. Schuur, M. S. Bret-Harte, G. R. Shaver and F. S. Chapin, III. 2004. Ecosystem carbon storage in Arctic tundra reduced by long-term nutrient fertilization. Nature 431: 440-443. Also commentary by Loya and Grogan.

Walker, M. D., C. H. Wahrenb, R. D. Hollister, G. H. R. Henry, L. E. Ahlquist, J. M. Alatalo, M. S. Bret-Harte, M. P. Calef, T. V. Callaghan, A. B. Carroll, H. E. Epstein, I. S. Jonsdottir, J. A. Klein, B.. Magnusson, U. Molau, S. F. Oberbauer, S. P. Rewa, C. H. Robinson, G. R. Shaver, K. N. Suding, C. C. Thompson, A. Tolvanen, Ørjan Totland, P. L. Turner, C. E. Tweedie, P. J. Webber, and P. A. Wookey. Plant community responses to experimental warming
across the tundra biome. Proceedings of the National Academy of Science 103: 1342–1346.

June 21. Field exercise: Consequences of shrub expansion
Question: Will shrub expansion accelerate further Arctic climate warming?

Issue: Trees and shrubs are expanding into areas previously occupied by low-stature tundra vegetation. This shrub expansion is potentially linked to changes in Arctic climate because generally dark-colored shrubs decrease the reflectance of light, or albedo, from the ground surface. This effect may increase local atmospheric heating as much as the effect of increased CO2 in the global atmosphere. While the effect of tree expansion on Arctic energy balance is large, it will take decades to occur because tree migration and growth in the Arctic are slow. The effect of shrub expansion is smaller and more subtle, but it may occur much more quickly. Shrubs may have a number of influences on ecosystem processes. For example, if more snow accumulates around shrubs, it may moderate the effect of decreased albedo, especially in the early growing season.

Activities: We will examine the effects of increased shrub cover on the microclimate, soils and vegetation of Arctic tundra. We will work in another set of plots as part of the Arctic Long-Term Research site. We will compare plots of heath tundra that have been fertilized with nitrogen and phosphorus since 1988 and control plots that have received no fertilizer. The fertilized plots contain substantially more shrubs than the control plots.

We will measure both air and soil temperature in both treatments using recording temperature dataloggers, and we will measure soil moisture with hand-held moisture probes. We will quantify differences in plant species by making non-destructive estimates of the cover of individual species. Because detecting shrub cover from satellite is critical for estimating increased shrub cover over large regions, we will use a hand-held device to record normalized difference vegetation index (NDVI), a very useful parameter that can be gathered from satellites. If snow is still present, we will record snow depths and calculate differences in snow water volume in the two treatments. We will discuss the potential feedbacks between increased shrub cover, temperatures and what they will mean in a future warmer Arctic.

Key readings (click links for pdf file)
Chapin, F.S., III, M. Sturm, M. C. Serreze, J. P. McFadden, J. R. Key, A. H. Lloyd, A. D. McGuire, T. S. Rupp, A. H. Lynch, J. P. Schimel, J. Beringer, W. L. Chapman, H. E. Epstein, E. S. Euskirchen, L. D. Hinzman, G. Jia, C.-L. Ping and K. D. Tape, C. D. C. Thompson, D. A. Walker and J. M. Welker. 2005. Role of land-surface changes in Arctic summer warming. Science 310: 657-660. Also commentary by Foley.

Wahren, C.-H. A., M. D. Walker and M. S. Bret-Harte. 2005. Vegetation responses in Alaskan arctic tundra after 8 years of a summer warming and winter snow manipulation experiment. Global Change Biology 11: 537–552.

June 23. Introduction to Excel and data analysis.
We will work in the laboratory to enter, analyze and interpret data. We will take a break and hike to fascinating “aufeis” in the afternoon.

June 24. Field exercise: Permafrost melting
Question: Will rapid permafrost melting decrease soil carbon and increase nutrients released to streams and rivers?

Issue: Warmer temperatures in the Arctic are melting permanently frozen soils (permafrost) in many locations around the world. Permafrost melting exposes long-frozen soil and accelerates decomposition that can release CO2 or other greenhouse gases like methane (CH4) to the atmosphere. Permafrost melting may also liberate nutrients such as nitrogen and phosphorus contained in old and formerly frozen soil organic matter. If permafrost melting becomes more widespread, nutrient export to streams and rivers may increased.

Activities: There are several thermokarst features near Toolik Lake. Thermokarts are land surfaces that form as ice-rich permafrost melts. We will visit a thermokarst site that has been measured over several years. We will measure the size of a thermokarst. We will measure the depth of soil horizons and soil water and carbon content. We will use estimates of soil nitrogen and phosphorus content to estimate carbon and nutrients released from permafrost melting.

We will also measure sediment, nitrate (NO3-) and phosphate (PO43-) in the water track (small stream) that drains the thermokarst and compare them to a similar water track in an adjacent area of remaining tundra that still overlies permafrost. We will also measure sediment, NO3- and PO43- in the Toolik River above and below its confluence with the thermokarst water track to determine the effect of this melt feature on larger rivers.

Key readings (click links for pdf file)
Zimov, S.A, E. A. G. Schurr and F.S. Chapin, III. 2005. Permafrost and the global carbon budget. Science 312: 1612-1613.

Peterson, B.J., J. McClellan, R. Curry, R.W. Holmes, J.E. Walsh and K. Aagaard. 2006. Trajectory shifts in the Arctic and subarctic freshwater cycle. Science 313: 1061-1066.

Bowden, W. B., M. N. Gooseff, A. Balser, A. Green, B. J. Peterson and J. Bradford. 2008. Sediment and nutrient delivery from thermokarst features in the foothills of the North Slope, Akaska: Potential impacts on headwater stream ecosystems. Journal of Geophysical Research 113, G02026, doi:10.1029/2007JG000470.

June 25. Field exercise: Eutrophication of Arctic fresh waters
Question: How will increased nutrients from land alter the structure and functioning of Arctic rivers?

Issue: Arctic waters are generally oligotrophic, meaning nutrient poor. This means small amounts of nutrients can have large ecological effects. One of the first long-term experiments to investigate the effects of increased nutrients in Arctic fresh waters took place in the Kuparuk River near Toolik Field Station. Small amounts of phosphorus have been added to the Kuparuk each summer since 1983. This has led to dramatic changes in stream food webs leading to the river’s most important river fish, Arctic grayling.

Activities: We will measure steam cross sections and stream velocity to calculate discharge. We will use upstream (control) and downstream (P-fertilized) reaches to examine effects on moss cover and moss biomass. We will also collect aquatic invertebrates and compare between reaches and view adult and young-of-the-year grayling.

Key readings (click links for pdf file)
Peterson, B. J., L. Deegan, J. Helfrich, J. E. Hobbie, M. Hullar, B. Moller, T. E. Ford, A. Hershey, A. Hiltner, G. Kipphut, M. A. Lock, D. Fiebig, V. McKinley, M. C. Miller, J. R. Vestal, R. Ventullo and G. Volk. 1993. Biological responses of a tundra river to fertilization. Ecology 74: 653-672.

Slavik, K., B.J. Peterson, L.A. Deegan, W.B. Bowden, A.E. Hershey and J.E. Hobbie. 2004. Long-term response of the Kuparuk River to phosphorus fertilization. Ecology 85: 939-954.

June 26. Sample and data analysis
We will use this day to finish the laboratory analyses we began during the previous field days and entering and analyzing and graphing data in Excel spreadsheets.

June 27. Data analysis and presentations
We will use this day to interpret data produced during the field collections and to build 10-minute Power Point presentations to explain what you found to your scientific peers. Instructors will work with students individually to discuss and help them construct the presentations.

June 28. All-day hike in the Brooks Range.
This will be a day of intellectual rest but physical rigor. Hikes will be available to suit different levels of physical ability.

June 29-July 1. Interviews and field visits with Toolik researchers.
Travel to Prudhoe Bay oil fields on one of these day.

July 2. Depart Toolik