The McMurdo Dry Valleys Long Term Ecological Research (MCM-LTER) project is initiating a new long-term experiment in which we will experimentally wet soils in a controlled manner. The 3 P’s of “P3″ are Pulse and Press Project. We expect that as this region warms in response to global warming (albeit slowly given all of the ice in Antarctica), there will be more melt occurring on the glaciers that exist in the mountains around the valleys, and the meltwater will reach soils that had previously been generally dry. How will those soils respond hydrologically, biologically, and biogeochemically?
We will be using this blog as a means of communicating within and beyond our group of our activities at the site. Each time a group visits the site, they will post to this blog their activities, when they visited, and whether everything was fine or they saw anything unusual. This will serve as an archived record of the experiment as we move forward with it.
We have established 3 plots (~5 m wide and 15 m long) on a hillslope adjacent to Many Glaciers Pond near the mouth of Taylor Valley. One of these plots will be a control plot (the C-plot), which will be instrumented and sampled, but it will not be treated, one will be the press plot (the H-plot, for high water application) and it will receive controlled water application each season, and the third plot will be the pulse plot (L-plot, for low water application) receiving water application once every 2-3 years. Water from the pond will be pumped uphill into a 1000 gallon black plastic tank and then slowly released by gravity from the tank into a trench approximately 3 m above the press and pulse plots. As the water leaves the tank, it will flow through a UV irradiance system (inline) in an attempt to kill off any bacteria or plankton that are collected from the pond. In this way, we can ensure a more pure treatment to the soils. That is, any response of microbial community changes in the press and pulse plots can be attributed to the effects of the water, rather than introduction from the pond.
Time 0 Sampling – prior to 01 January 2012, we sampled soils in 4 longitudinal transects extending from uphill to downhill at every meter along the length of the plot (i.e., 4 ‘replicate’ samples from the same distance down the slope of the hill).
Instrumentation – from 08-10 January 2012, we instrumented one transect of each of the plots with thermocouples (to measure soil temperature), soil moisture and temperature probes, and soil tension sensors. All sensors are connected to multiplexers and a single Campbell Scientific datalogger at each plot. We expected to instrument our sites with a combination of soil moisture and temperature probes at 5 cm, 20 cm, and 35 cm below the soil surface, but soil thawed depths were generally less than 20 cm.
Surveying – on 10 January 2012, using GPS survey equipment from UNAVCO, we surveyed each sampling point within each of the 3 plots.
Time Lapse Cameras – we have deployed time lapse cameras (taking a picture every hour) at these sites. As we gather those images we will generate movies of the changes at the site and post them below. Please check back!
We did not apply water to the H or L plots this austral summer. The reason for this is that, for a long-term experiment, it is important for us to characterize the variability in the background conditions so that we can better determine the change from the background conditions. We have a time zero sampling of the soils across the plots, and we have initiated soil temperature, moisture, and tension data every 30 minutes, which will be continuous (even through the winter). Next austral summer we will take another preliminary set of samples and apply water to the H and L plots.