May 26, 2012 Plucking Soil
Today turned out to be a good day for inside work in the lab. Early morning brought an inch or so of snow covering the ground; the overall effect was quite beautiful and I was really tickled to get to see fresh snowfall in the Arctic!
Our team spent the morning together in the lab; beginning with a task called plucking. This involved taking the soil cores bagged up yesterday afternoon and sorting the obvious living material out of the soil, leaving a conglomerate of soil and dead organic matter called soil organic matter (SOM).
This became our usable sample, which we proceeded to separate into categories depending on what information we wanted from the soil subsamples.
Different weights of the subsamples went into different containers depending on the tests to be run: enzyme assays to measure enzyme activity, samples treated with chloroform in order to inventory microbial biomass (mass of (formerly) living microbes), and other samples weighed out for soil respiration measurements as well as soil moisture content.
While others kept working in the lab, Caroline and I carried a few of the more beat up soil coring samplers over to the shop to re-sharpen them and even cut off the ends that were too bent to be re-used.
You can see Caroline sharpening the sampler ends at the grinder, and myself cutting off a really beat up end with the Sawzall.
Thank goodness for shop tools and thanks, Gary from the Toolik Field Station staff, for the timely Sawzall and drill press lesson!
The question is, why are we looking so closely at this soil from the tundra? Arctic soils are holding very large stores of carbon. As the soils warm, given a longer and/or warmer growing season, the possibilities of carbon release from these soils will increase. How did all that carbon get there in the first place?
Antlers and even bones are easy to find in the tundra since they take so long to decompose. All living things are essentially made of carbon, and if they haven't decomposed as fast as they've grown, stores of carbon will, and have, accumulate. Remember, we are north of the Arctic Circle, and right now experiencing days of long sunlight; between today, May 26 and the 17th of July, the sun will never set. That's a nice long growing season for the tundra plants here. We all know what happens to plants and living things that die, they will decompose, right? Where do you put your fresh vegetables from the store so they won't rot so quickly? In the refrigerator, of course! Think Arctic, and think giant refrigerator. So, all these plants have been growing and dying for thousands of years, and decomposition rates have not kept up with plant growth. Thus, Arctic tundra soils have a high carbon content. We are trying to better understand the mechanisms that control plant growth and decomposition, and a very good place to study that is in the plant roots and soil samples that we have been processing. This is the story I've come here to learn about and share with you this summer. There are many facets to the research project I'm assisting with this season. I'm looking forward to better understanding this science behind and the procedures used in finding answers to how changing climate is affecting plant growth and decomposition rates in the Arctic tundra.