Plant placed in the cuvette for respiration measurement
According to one online dictionary, respiration is the act or process of inhaling and exhaling, such as breathing. How can an ecosystem breathe, you ask? It's really quite complicated, and also quite simple. For the big picture, think of all the plants and all the animals going through their respective gas exchange processes. We know that plants take in sunlight and also CO2, combine it with water, and make their own sugars and oxygen molecules; that's what photosynthesis is! We know that you and I, and all the other animals we can see and a whole lot that we can't, take in that oxygen in order for us to live and breathe, plus we eat the plants which are sugars and starches made up of carbon, hydrogen and oxygen, and turn food into energy we can use. That's respiration! We exhale the carbons and water, and voila! Plants are there waiting to capture that CO2 and the cycle of photosynthesis /respiration continues. By the way, plants are respiring too; they also need to convert their sugars to energy they can use. That's why we call it gas exchange. A third leg of all this cycling is when animals and plants die and decompose; the decomposers including bacteria and fungi break down the bodily structures of the animals and plants, thus breaking down the carbon compounds and returning them to the atmosphere and soil.
jawbones on the tundra
Remember, in this tundra arctic ecosystem, decomposition occurs more slowly than in other ecosystems; the pace of growth is much faster than that of decomposition.
All of that is pretty complex, really, but wait! Now we need to get started talking about ecosystems…and we generally think of them as all the living and non-living organisms interacting together in a given environment. For example, a tundra tussock ecosystem (come on, you know all about tussocks) (or you can review the journal: Science Friday) includes the plants such as cottongrass, mosses, lichens and a whole lot of really pretty wildflowers
Pedicularis blooming on the plots
the animals, including that caribou over there
caribou walking near our research plots
the soil and it's world of life, water, immediate atmosphere, and anything else like rocks that happen to have an influence on the whole works.
So, there we go, we've got respiration figured out, and also ecosystems. For a bonus, you even remembered what photosynthesis is and learned about the carbon cycle. I snuck the carbon cycle in without telling you; that was the part where you could just follow the carbon through the atmosphere, plants, non-plants, and soil. Here's a carbon cycle, now, thanks to fellow PolarTRECer John Wood The Carbon Cycle
an illustration of the carbon cycle, courtesy of John Wood
You can take a look at the diagram and get an idea of the ins and outs, so to speak, of the global carbon cycle.
Now we are getting closer to the research project I'm working on. The other day I got a chance to work with Alex Krichels,
Alex identifying plants using the point frame method
an REU student recently arrived to work on the project. REU stands for Research Experience for Undergraduates, which is a really fantastic program that pairs college students with field experiences in their major course of study, helping them to gain valuable research experience on many levels. Alex is working for another one of those six scientists on our project, Dr. Patrick Sullivan of the University of Alaska, Anchorage. Alex got his first hand training on his work this summer from Aliza Segal, a Masters student under the advisement of Dr. Sullivan. Aliza was here for a jam-packed week of work and training of Alex, and then she zoomed back to UAA to defend her thesis
Aliza with an ecosystem respiration chamber setup
Way to go, Aliza! Aliza is working on figuring out as much as possible about the respiration of many separate parts of the tundra ecosystem. On the day I helped, Alex was taking respiration measurements of stems of four different flowering plants. He took these sets of four measurements eight times right near our study plots; this allows him to get a good number of repetitive measurements to insure an accurate assessment, without stomping all over the plots and destroying them. He and Aliza are working on getting an idea of individual plant respiration amounts to develop baseline information for one of the many parts of this big ecosystem respiration exchange of CO2 picture.
First, Alex finds a nice representative plant sample of one of the species they are looking at, in this case, a small birch tree
inserting Betula stem into cuvette to measure respiration
He places the stem inside a small clear plastic box, called a cuvette. The cuvette traps gases in the now sealed chamber, and the attached Li-COR Infrared Gas Analyzer is able to measure the gas, such as CO2, absorbed by infrared radiation in the chamber, thus calculating a measurement of CO2 being exchanged by the stem. After measuring, he will cut that exact stem and bring it back to the lab for weighing; this allows them to get an idea of how much biomass there might be in birches in this ecosystem, and then calculate the amount of CO2 currently being exchanged by birches, as opposed to other species such as willow or cranberry.
the field set-up for measuring stem respiration
Another method scientists use to determine the species composition and whether or not they are looking at proper proportions of plants is to use a point frame.
the point frame
In this setup, Alex checks to identify all the plants that touch the bar he lowers into the plot. The strings and squares allow him to make a systematic survey of a small plot. This method estimates species composition, and also amount of coverage by the plants within subplots of the study area, creating a minimal amount of disturbance. Repetitions of this process over many weeks will help in the development of a species composition balance, which in turn will help in calculations of the plant part of the CO2 exchange process.
Ecosystem respiration, it turns out, is a process necessary to understand as scientists work to determine the balance of carbon in the ecosystem. Determining the amounts of CO2 exchanged by plants is one part of a complex equation looking at the dynamic interactions of all parts of an ecosystem, including the soil and its living organisms; and the plants including their roots, stems and leaves. Another big factor in determining the carbon balance in the tundra ecosystems is the amount of nitrogen in the soil; it affects both plant growth and decomposition. The research efforts of this study are primarily focused on the nitrogen availability in tundra soils, but understanding a little about the carbon cycle and respiration is an important first step in putting the big picture of all this research together. Can you see how the process of ecosystem respiration is both simple, in terms of thinking about it, and also very complex, especially when trying to measure it in real life! Fortunately, these scientists have real passion for their work, and I must say, every day in the field is not only a great learning experience for me, I also always enjoy the ever-changing views!
Alex at the point frame, me taking notes