I am very interested in botany, plants and ecosystem structural dynamics (some people may go further and replace “interested in” with words like “obsessed with” or “a fanatic of” so those who know me can fill in their preferred word), so it was a dream come true to study this in Sweden.
My project looks at the vegetation diversity and abundance across five ecosystems in Stordalen Mire: palsas, eriophorum-dominated fens, sphagnum peatlands, lakesides and lake heath.
These ecosystems I am studying differ a lot in several aspects, including water availability, limiting growth factors, and nutrient cycling. For example the palsas, which are mounds of permafrost with a thin layer of peat and specific vegetative species, are ombrotrophic, meaning they receive all their water and nutrients from precipitation. Stable palsas are generally drier, so there are a few species that initially colonize the mounds, such as Empetrum nigrum, Crowberry, which is tolerant to cold, dry and nutrient-limited conditions. With palsa aging or permafrost thawing the moister conditions allow further species colonization.
By identifying the species diversity and abundance on a quadrat-transect system , I hope to find how vegetation differs across these ecosystems and how the mire may respond and evolve in terms of vegetation as permafrost thaw and climate change impact continue. Even though on a cold day Stordalen Mire appears silent and lifeless, there is so much life everywhere with birds, insects, an impressive diversity of plants, rodents moose and reindeer, and everything is interconnected. So as the vegetation dominance and presence change, so will the whole ecosystem.
The subarctic ecosystem is a really interesting environment so I will be explaining some things as I introduce the study sites:
A mound of permafrost with a thin layer of organic matter (peat) on which plants grow. They are created when an ice lens is formed and frost heave puts uplifting pressure on the soil and the mound is created. The height of the mound preserves it, since the wind blows the snow off the surface and prevents the isolating affect of snow that would otherwise warm the palsa and induce permafrost thaw. In the summer months, the vegetation similarly protects the permafrost from thawing from the sun’s rays and heat.
There are various zones of permafrost, some areas have continuous, meaning it is almost completely present in the landscape, discontinuous (like Abisko) where it is mid-high present, and sporadic when it is mid-not at all present in the landscape. With warming temperature and new climate change events, studies have observed a thawing of the permafrost in the palsas.
There is an interesting range of plants here, which include Andromeda polifolia, Rubus chamaemorus, Betula nana, Empetrum nigrum, sphagnums and lichens. Ombrotrophic, meaning the nutrients and water received are solely from precipitation.
This ecosystem is known as the “encroaching fen” because it is creeping into the palsa environment as it becomes more humid. The two dominant species are Eriophorum vaginatum and Eriophorum angustifolium, two species of cotton grass that establish themselves quickly in wet areas in thick grassy clumps. The sites I picked were very clearly dominated by Eriophorum, but I could see just by walking around Stordalen that these grasses were encroaching in a lot of other areas and out-competing other plants. Abisko is supposed to be pretty dry in the summer, but with all the precipitation events the Eriophorum definitely got a competitive edge. Something to think about in terms of future climate change impact on the mire.
Mostly sphagnum moss in these areas, some species preferring tight drier hummocks (Sphagnum fuscum) and others wet floating clumps (Sphagnum balticum). I noticed mostly the latter was dominant in Stordalen, perhaps because of the unusual precipitation event and late winter.
The lake had two distinct parts, so I decided to split it into two distinct ecosystems:
Slightly flooded over and wetter, it was dominated by plants like Salix lapponum, Equisetum pratense and graminoids like Carex sp.
This is the shrubby area right beyond the lake edge that is generally drier and hosts a different range of vegetation like Betula nana and Melampyrum pratense.
The design of my research was to run six replicates of each ecosystem with a seven meter transect with 3 one-meter squared quadrat in each transect. I identified all the species in the quadrats and estimated the percent cover of each species
I had a wonderful time out in the field everyday in the beautiful Stordalen Mire and learned so much! I can’t wait to analyze my diversity and abundance data and draw conclusions on my findings!
I could not resist ending without some lovely plant photos!!!