May 30, 2012 Soil Extraction
Over two days we collected soil samples at each of our six sites. We will collect soil samples each time before we do nutrient uptake experiments so that we can estimate the pool of available nitrogen and phosphorous. We also had another addition to our team in the last week. Margit, who is an undergrad at University of Alaska-Fairbanks, join us. As an undergrad, she has already had lots of great experience in the lab and the field and has been a great help to the team. You will see her collecting soil samples below.
Since most of the ground is still frozen, we can’t use the soil core tool yet. To collected soil we used a kitchen knife to cut a square that was roughly 10cm by 10cm. We collected 5 samples at each site starting at the bottom of the water track and working our way up to 75 meters above the weir. We try to get a representative sample of the various types of vegetation throughout the water track.
Once the sides are cut, we cut underneath to be able to pull out the soil brownie. Some of the soil samples were mossy and others had more sedges. Some had light brown soil, while others had wet dark soil.
Then the brownies are placed into labeled ziplock bag. We also measure and record the length, width and depth of the soil sample. Additionally we measure how much of the sample is alive verses dead and make note of the vegetation in the sample. The samples ranged in depth from about 6 cm to 15 cm. In the photo below the knife is stuck into the frozen ground at the bottom of the soil sample.
Back at the lab
When we return from the field, we put the soil samples in the refrigerator until we can process them. Once ready to process, we mass 10grams of soil and mix it with a calcium chloride solution (CaCl2) and shake well. Gravity is used to filter the solution because there can’t be any chunks in the liquid that is run through the machine in Fairbanks.
This measurement goes into a model that helps Tamara calculate the abiotic verses the biotic uptake of phosphorous.
To see a video of extracting soil brownies, you can go to this link: http://www.polartrec.com/expeditions/nutrient-transport-in-arctic-waters...
Question to Ponder- Discussion
From QTP on May 27
I asked With 24 hours of sunlight, do plants photosynthesize at the same rate all day and night? Greg Starr has found that plants do not photosynthesize at the same rate when there is 24 hrs of light. The plants still have a built in “clock” that allows them to adjust to photosynthesize the most during the times when the sun is the nighest in the sky, which is from about 10am to 2pm. Outside of those times, the rate of photosynthesis drops off.
From QTP from May 28
The tracks in Atigun Gulch were from an Arctic Ground Squirrel (Spermophilus parryii) also called “sik sik” by the locals because of the sounds they make. There is a group studying the ground squirrels up here. These squirrels do hibernate, but they are out running around now.