7 July, 2001
We awoke to a gray sky and snow flurries falling, all day. Two good things about that; little to no wind and no mosquitoes! After lunch we had alot of things to do in the field. We went out and spent all afternoon on various projects.
Lety is studying soil respiration. She has set up her study areas (8 plots) this past week and began taking measurements today. When studying carbon dioxide flux there are two processes where carbon dioxide is exchanged from air to plants and vise versa . First in the process of photosynthesis, which we normally think of as the daytime growing process when plants take in CO2 and act as "sinks". The second CO2 exchange takes place in darkness, when the plants go through the process of respiration, the giving off of CO2 to the atmosphere. During the latter, the plant's vascular, aboveground parts and the plant's below ground parts, the roots, give off CO2. In the arctic, where 95% of an entire plant may exist below ground in its root system, measuring soil respiration is important when calculating the carbon budget of the ecosystem.
Lety has isolated two areas per plot and defined them using two 4inch round PVC pipe sections placed in the soil to a depth of approximately 2 inches. One circle she placed over undisturbed plants and in the other she has removed the above soil, plant parts. Using the LiCor, which we use during diurnals, she covers the PVC sections with a "mini cuvette" (pictured below) and measures the CO2 each circular area gives off. The carbon dioxide comes from a number of sources: respiration of roots, decay of organic matter and the activity of microbes. The amount of moisture in the soil also is important when measuring CO2 in the soil. Empty pore spaces can contain gases. When soil moisture is high the pore spaces are filled with water, displacing the gas. Soil respiration is very dependent on soil temperature, organic matter, moisture content and precipitation.
The picture below shows Lety taking measurements with the small white chamber (LI 6000, soil respiration chamber). One important thing she also has to do is account for the CO2 in the chamber when placing it on the sample. She does this by running the pump and scrubbing the existing CO2 out of the closed system before taking a measurement.
Lety recorded her first round of measurement s today and made it to all the 8 plots in 2 hours. She will take 3 measurements at each in the next few days but now she wants to check the data she is generating against Glen's first to see if things are working correctly. The numbers she will get will not be the same as Glen's numbers but should be somewhat similar. It's always convenient to have something or someone to compare to when you are initially taking measurements.
Finding out soil respiration is important for understanding where the carbon is coming from and whether the processes you are studying are a net source or sink for the carbon in the atmosphere.
Glen also was gathering data at his site today using the LiCor to compare his control plots with the heated plots to see what effects the treatments were having on the carbon fluxes. Along with them were Stan and Erika taking LiCor measurements at the CA. State LA site. They are measuring species-specific fluxes. So every one was measuring fluxes of one sort or another all afternoon.
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