Carbon and Nitrogen Cycles

Joined: 23 Mar 2004 Posts: 24

Well, after a week of plucking specific plants from the test plots we've moved on to a different phase of the project.
The focus of this one is detecting and measuring nitrogen in the soil.
Nitrogen, and the various molecular forms it exists in naturally, and how it interacts with carbon, can tell an ecosystems scientist a great deal.

Charged resin bags planted in the soil behave like plant roots and can be removed to detect nitrogen in its different forms as it cycles through the soil. We planted multiple sets of these tea bag looking detectors in all of the test plots to measure the cycling nitrogen and how it varies with the different plant removal treatments that were previously done.

The next phase was to use metal corers to sample soils. From each plot one core was taken back to the lab, and another core was placed in a plastic bag and replaced in its hole, to be retrieved in 30 days. Analyses of these two samples can be compared with one another. Results should determine how much plant available nitrogen there is that is "fixed" by microbes (bacteria and fungi) in the soil through a process known as mineralization. The amount of nitrogen made by this process is limited by the amount of carbon that is available. This is a complex system of carbon nitrogen ratios and relationships.

One implication is that as temperatures warm in the Tundra, carbon and nitrogen cycling is sped up, and more carbon is respired into the atmosphere. Because carbon, as carbon dioxide, is a greenhouse gas, the present warming would create even greater warming. Tundra, with its cold soils, has historically been a carbon sink due to its slow rate of decomposition of plant matter. The idea that the thawing tundra could release more carbon than it holds is the source of much current research.

The work that is being done here by Dr. Mack and Dr. Bret-Harte is a piece of the climate puzzle. It is fascinating to be involved in such cutting edge science. When plucking plants or bagging soils starts to feel a little tedious I just have to ponder the big picture and I feel privileged to be a small part of it all.

Laurie Carr burying the resin bags 5cm-8cm into the soil, and marking the spot with a flag.

Measuring permafrost depths, which vary from 3cm-30 cm this mid-June.

Dr. Michelle Mack and Research Assistant Stephanie Juice done bagging soil for the day!