It seems like I should introduce my field site, since it’s the whole reason I’m here this year. Welcome to Petsikko (pet-see-koh), as it’s called by locals here, which is a system of close-to-the-road wetlands in the higher elevations near Kevo. It’s 50km south of Utsjoki, and 25km south of the Kevo field station. There is a little path leading from the road out to the ‘wet places’, as the field tech here calls them. The wetlands are actually pretty extensive, interspersed with higher mounds and areas known as palsas (the little islands of soil in the wetness, shown below), some of which contain ice lenses, or permanent ice inside of the mounds. There’s no permafrost (permanently frozen soil) anywhere in Finland, but this is about as close as it gets. This is the view of the area from the road – my study area is just beyond where the telephone poles are):And as seen from the ‘start’ of my boardwalk system:
He is one of the Kevo field station’s field technicians. He and another of the permanent Kevo staff members built me these lovely boardwalks, which span the ‘wet places’, so that I can sample without being thigh-high in muck, and I will disturb the wetlands as little as possible. Esa came out and helped me install my permanent sampling collars in early September, as the day they needed to be installed was rather inconveniently the day after I had my stitches.These are the soil collars, aka: 125mm-diameter PVC tubing I sawed into 25cm lengths:
The collars are all buried 22 cm into the ground, and placed in pairs, so that when I inject treatments in the spring, one of each pair can serve as the unmanipulated, ‘control’ collar. Overall, I have 24 base collars that I’ll be monitoring this fall and throughout the winter. I have also installed 24 additional collars that mirror the 24 base collars on the opposite side of the boardwalks, as seen below. These mirrored collar sets will essentially act as another treatment when the snowmelt begins next spring. During winter, snow piles up against the windward-side of the barrier my boardwalks create, commonly referred to in science as a ‘snowfence treatment’. The treatment part refers to the fact that there is a slower melting of the snow on the snow-heavy side of the ‘fence’ (or for me, the boardwalk). The snowier side melts slower because snow has a high albedo, meaning that the sun’s energy is mostly reflected back into the atmosphere when it shines on snow. This is in contrast to something with a low albedo like dark pavement that absorbs a lot of the sun’s energy, which is what makes roads so warm on sunny days. So the more heat-reflecting snow that’s on the ground, the cooler the ground beneath it remains, and the longer the snow can persist before being melted. Thus, the ‘snow fence’ treatment is a common way to study the effect of longer, thicker snow cover (a possible effect of climate change in some areas).
There are 4 sections of boardwalk, only 2 of which have collars along them – the other 2 sections are necessary to get from one side of the wetland to the other, but the water is too deep for gas sampling (collars can’t be underwater and still get a good seal). There are 8 collar pairs along the first boardwalk……and 16 pairs along the fourth boardwalk, for a grand total of 48 collars.
I also have a porewater sampler installed inside each collar. When I say ‘porewater’, I am referring to the water that’s in the empty spaces within the soil. Microscopically, soils are a lot like Swiss cheese – there are soil particles that are solid, but there are also a lot of empty spaces, or pores. In dry soils, these are filled with air. In wetland soils, these pores are filled with water. The porewater samplers are nifty little doodads. They have a 10cm-long porous surface attached to a flexible tube and then a needle.I can put a blood collection vial on the needle, and the suction created by the vacuum inside the blood vial actually sucks the water out of the soil surrounding the porous section, kind of like a ceramic water filter. So I bury these so that only the porous section is under the soil surface, and then the samples I take are representative of the porewater in the top 10cm of the soil! I can test the concentration of gases inside the porewater, as well as a number of chemicals that indirectly indicate microbial activity levels. I certainly had no idea that I would be so familiar with blood vials when I started my PhD in ecology, that’s for sure!
For wintertime sampling, I have placed construction-orange poles with reflectors 30cm to the left of each collar pair. This way, I can ‘find’ the location of each collar when they’re buried under (up to) 1m of snow. I won’t actually be digging out the collars to sample in the winter, but rather I’ll seal the cap to the snow directly above each collar, and measure the gas flux that’s escaping through the snow cover. The reflectors are nice because it’ll also be dark. I’m not sure I fully internalized the concept of winter sampling – 8+ hours of near inactivity in bitter cold, and all in the dark. I really should have passed on watching that vampire movie set in the dark winter of the Arctic….
So my weekly sampling stars this cap. The lowest part of the cap fits snugly into each collar, with a (currently red) rubber band at the seat to make it seal. For the curious, there are 2 rubber septa (the black dots), into which I can insert needles for sampling and venting (the venting is important so that there is neither a gas buildup nor a vacuum created while the cap sits on the collar).
Once the cap is placed on the soil collar, I take a series of samples of the gas from the ‘headspace’, or the area inside the cap, which is tall enough to accommodate the plants growing inside the collar.
I sample with a needled syringe, which I insert into one of the septa on the cap top (remember the other septa has just a needle which allows for venting), draw a sample into the syringe… …and then inject into a sample vial, which will store the sample until I can analyze it on a gas chromatograph in the lab.
I take a sample of the headspace immediately after I put the cap on, leave the cap in place for 30 minutes, and take a second sample. After analyzing, I know the amount of methane and carbon dioxide in both samples (initial and final), and I can solve for the ‘flux’, or the amount of methane and CO2 that was emitted from the soil during a known period of time (the 30 minutes). Welcome to climate change science!While the caps sit on the collars, I have about 20 minutes of time to do other sampling and site maintenance before I have to move the caps to the next pair of collars. Right now, I’ve mostly been taking soil cores so I have some soils to analyze in the lab during the winter. This may be counter-intuitive, but sampling wetland soils is a big ol’ pain in the rear. Yeah, sure, it’s (relatively) easy to insert the corer, but wet soils have this pesky habit of self-ejecting when you pull the corer out of the ground. This is a shot of the engaged corer – I use that giant knife to saw along the sides of the corer as I place it, to guide the corer and minimize soil compression. Then I use the mallet to pound the whole contraption down into the depths – this is hard, no matter how wet the soil is.And I fell into the classic trap of the shiny when I chose a corer from the Kevo field equipment stash. Corer #1 has a window, which means that you can see if you were successful when you bring the core out, and there’s a plunger, so that removing the core from the corer should be a breeze. It seemed like such a slick idea. After 2 weeks of trying to use this POS, I’m left wondering if there is any soil type that this window-corer would work for. Oh, sure, it’s cool to see the core you successfully extracted, but once that self-aggrandizing moment passes, you’re left with trying to get the dratted thing out.Plunger, you say?? Yeah, there are 2 problems with the plunger. Problem #1: One person can only do half of the necessary movements required, namely you can either depress the plunger, or you can ‘catch’ the core – I felt like I was taking ‘dirt yoga’ trying to exert enough force to push the core out while also keeping the core intact and contained within the plastic receiving bag. And this contortionist act is complicated by corer problem #2: the unavoidable escape of the core through the window when you’re depressing the plunger. I can’t tell you how many cores I took that ended up as multi-target projectiles – half out the window and all over my legs, and the other half out the end, generally shooting into the air and raining down on me. I’m purposefully not including pictures here. :)
So back to the field equipment closet I went, and I found the slightly-smarter version of the same corer, aka: there’s no window. I have also found that the only way I can depress the plunger without gaining a multicolored badge of idiocy on my ribs the next day is to put the whole contraption upside-down, so that I step on the corer handle to depress the plunger, and then I have my hands free to grab the core with the plastic bag as it’s released. This is not a perfect system by any stretch of the imagination, but there’s way less bruising and mud-rolling! It’s times like these when I wonder why everyone doesn’t want to be a field ecologist….
So when you’re lucky, and freakishly coordinated, you end up with an intact core! You’re not surprised anymore that it takes me all day to get half a dozen of these, are ya? This is a core from a moist (but not waterlogged) area of the wetland – the lighter, spongy-looking stuff for the first dozen centimeters is Sphagnum moss that’s still alive. The darker area below is the same stuff, but old, dead and compressed over long times.And an unexpected aspect of doing science in Finland is that ziplock bags aren’t involved. Instead, plastic bagging comes in large, un-perforated rolls, which you cut to the size you want (you buy by the tube diameter). So both ends have to be secured by twisty-ties, and you end up with what I’ve affectionately termed ‘tootsie rolls of science’!So that’s my field site and current work in a nutshell. I will continue sampling once a week until the ground is completely frozen, which will hopefully be soon (cross your fingers). I’m doing this because there is some question about exactly how carbon gas fluxes work when the ground is freezing – does the freezing push the gases out of the soil and into the atmosphere? Or does the ground freezing trap the gases in the ice, to possibly be released in the spring when the soils thaw out? We (in the royal sense) care how this works so that we can better understand how carbon cycling will change when climate changes.
Once the ground is totally frozen, I’ll only be sampling once a month. I’ll start the more frequent sampling again when it gets on to the thaw around May, and then continue sampling throughout the summer months.
Anecdotally, I’ve started to experience a little of the winter weather in the field. My field day last week started with a short snow flurry (which stuck but mostly melted under the sun throughout the day), and ended with a fast freeze. It was a lot like those disaster movies about ice ages, where the temperature drops so fast that you can actually see the ice forming on things. It kinda freaked me out, actually. The sun set at around 5pm, and I still had about an hour and a half of work to do, and then a frost started forming on all my equipment, my samples, the water and soil surfaces within and around my collars, and then my collars began freezing to the caps during samplings! This is a picture of the sunset as seen through one of my freezing water samples.So let me know if something didn’t make sense, or if there’s anything you want to know more about – I should be able to address either. :)