By Liz Kalaugher
It’s not just humans and animals who can affect plants – Earth system processes, whether caused by water, frost, snow or wind, do too. Miska Luoto of the University of Helsinki showed me some of these in action when he assessed topography and disturbance at some of the team’s independent transect sites near the fells of Korkea (High) Jehkas and Iso (Big) Jehkas, where the vegetation had already been surveyed.
Luoto assigned a rating for the slope of each site relative to the surrounding area on a scale of one to ten, with one representing a valley bottom, 5 a slope and 10 a ridge. This meso-topography is one of the factors that the researchers are using to model species distribution.
Another is disturbance; Luoto assessed each site for geomorphological disturbance such as cryoturbation (frost churn), solifluction (a type of frost creep), nivation (snow-related effects) or deflation (wind processes), and for hydrological disturbance from water flow.
The first couple of metres of the soil here freezes every winter, creating seasonal permafrost. On the mountain peaks, above 800 m, there is permafrost all year round below a depth of about 2 metres.
Luoto says that to understand the landscape here you need to understand running water. A stream in the valley demonstrated how much difference water can make. The ground nearby is boggy, with many grasses, sedges, and herb species that would typically occur at lower altitudes. It’s standard for this area to have 8-15 plant species per square metre but by a stream that figure could rise to 40. A few trees are even creeping up the river; their presence can shelter other plants and increase snow accumulation in winter, providing extra protection from the cold. It’s a perfect illustration of why it’s important to take account of dispersal and species interactions when modelling the effects of climate change.
Earth system processes often occur together. We saw an area where bumps of soil have been pushed up by cryoturbation and have then started to creep downhill and form solifluction terraces. On the edges of the ridge, meanwhile, the wind has removed the fine sediment and only gravel and rock remain. Arctic alpine species typically like to grow at the edges of these disturbed regions.
Again, water is key to the heterogeneity of the landscape, Luoto explained. Not only does it play a direct role in vegetation growth, but water flow can also wash in nutrients. What’s more, water affects many of the earth system processes, as well as causing hydrological disturbance.
The plaintive whistle of a golden plover sounded out; later a pair flew high above, sunlight reflecting silver from the underside of their wings. As we climbed, the vegetation changed dramatically. It’s colder at higher altitudes so the growing season is shorter, and strong winds blow away the winter snow, leaving plants here less protected. The perennial shrubs, such as juniper and crowberry, that grow lower down don’t thrive and Arctic alpine species, such as white Arctic mountain heather, mountain avens, and Diapensia get a chance to shine. There are also lots of lichen and moss species, as well as grasses where it’s wet.
On the plateau it was almost barren except for a few hardy specialists. The white Arctic mountain heather was flowering; on Saana’s southern slopes it blossomed in early June – the differences in elevation and aspect have caused a two month delay. In the distance we could see the Norwegian border post, which has one of the highest saunas in the world.
Earlier we ate garden sorrel (Rumex acetosa subsp lapponicus) as a mid-morning snack. Once we’d climbed further, mountain sorrel was a tasty appetiser for lunch. We were too high up for a berry dessert, however.
After lunch we came across the site of a late-lying snowfield. It contained lots of moss as the growing season is too short for most vascular plants. In a boulder field I was introduced to the glacier buttercup, the most northerly vascular plant in the world. It can grow even in northern Greenland while in Europe it’s also the highest-growing vascular plant, reaching altitudes of more than 4000 m in the Alps.
Later we stood briefly in Norway. We didn’t go too far in as the border is close to the edge of the mountain. Luoto pointed out patterned ground, where cryoturbation has caused characteristic polygons.
I’d like to say a huge thank you to Miska Luoto of the University of Helsinki and his team – Peter le Roux, Heidi Mod, Julia Kemppinen, Pekka Niittynen, Jussi Mäkinen, Annina Niskanen, Joona Koskinen and Atte Laaka – for being great fun to spend time with as well as massively patient when I followed them around asking questions, and the European Geosciences Union (EGU) for providing me with a Science Journalism Fellowship to fund the trip. They say you can leave Kilpisjärvi but you always come back. I’m hoping that’s true.