Thursday, June 20, 2013

Tundra Tour, Toolik Talk

Today, Gus finished some of his LTER responsibilities early and had a little extra time. As a result, we were able to take a walking tour of the nearby tundra and get an introduction to some of the experiments that Gus and others have established over the years. We had already heard about his plastic tent warming studies and the many nutrient additions studies that have been initiated in dry heath and wet sedge tundra ecosystems. Some of these have been maintained for 20 years or more.
Our tour today touched on several other unique studies like those that use small plastic polygons or "ITEX chambers" to increase air and, to a lesser extent, soil temperatures around different plant communities. There is an international effort to deploy these ITEX chambers and Jeff Welker, Steve Oberbauer, Craig Tweedie and their colleagues have deployed a number of these at Toolik Lake, Barrow, and elsewhere.  We also viewed several snow fences that have been built in the area to examine increased snow cover and interactions among snow depth, soil temperature, permafrost thaw, and vegetation dynamics.


Lastly, Gus showed us structures that he and his students have built over the years to shade plants. The goal is to examine light levels and assess plant productivity across a range of light exposures. One might think that plant growth and biomass production would decline at low light levels, but apparently significant reductions in light can be tolerated by Arctic vegetation with little to no loss of productivity. The pivotal point here turns out not to be light per se, but instead the proportion of light coming as direct versus diffuse radiation. Plants are pretty efficient in using diffuse radiation for photosynthesis and biomass growth, so there is not a direct correlation between shade treatments and biomass growth.