We’re going to have to talk about snow. Snow is fabulous, it is unique, it is beautiful. But it also turns ecological processes and principles on their head: snow accumulation determines ground temperature, light conditions and moisture availability during winter. It also affects the start and the end of the growing season, and plant access to moisture and nutrients. And that critical role, which can give ecologists a bit of a headache, as snow is also highly elusive, and very tricky to measure (and not only because it is SO COLD to go out to measure in the Arctic tundra in winter).
The number of studies on snow has increased considerably in recent years, yet we still lack a good overview of how altered snow conditions will affect ecosystems. In a recent review, spearheaded by Christian Rixen from the WSL Institute for Snow and Avalanche Research SLF in Davos, Switzerland – as the name suggests quite the experts on the matter – we tried for the first time to create such a comprehensive summary.
We provided a ‘state-of-the-art’ of what we currently know about the snow cover’s role for vegetation, plant-animal interactions, permafrost conditions, microbial processes and biogeochemical cycling. With topics ranging from snow effects on temperature (buffering frost, but shortening the growing season), over light (increasing reflection of light away from the earth, and darkening the vegetation underneath it) to moisture (meltwater can provide vital but also short-lived water sources), we paint a picture of how snow is often the defining factor in cold-region ecology.
We also dive into the depths and complexities of what is happening (and will happen) with our tundra ecosystems as climate changes. Changes in snowfall and snow cover across the cold environments will be (and is) substantial, with both increases and decreases in amounts of snow. Effects of these changes are also not intuitive: less snow in winter may for example lead to colder soils as climate changes, as soils lose their insulating blanket. More snow in winter, on the other hand, generally has the opposite effect and causes warmer winter soils.
Finally, we took a good look at the ways in which scientists are currently experimenting with snow effects. Interestingly, we found that experimental research aiming to manipulate snowmelt timing worked with much smaller changes in snowmelt than those observed over spatial gradients (e.g. across a mountain slope). Indeed, experiments managed to change snowmelt on average 7.9 days (when aiming for faster melt-out) or 5.5 days (when aiming for delays). On the other hand, spatial variation in snowmelt easily reached up to 56 days, ten times higher! Similarly, snowmelt timing in the same location over time on average differed 32 days. Additionally, great differences could be found depending on WHEN in the season snow was manipulated. Here again, the main conclusion is: snow is complicated, even to manipulate!
If we want to get a better hold of snow and its mysteries, we will have to ensure a better comparability between studies. In this review, we have taken the first steps in that regard, by providing an improved baseline for future studies of the influence of snow. Differences between snow study approaches need to be accounted for when one wants to generalize conclusions and, especially, when projecting snow dynamics and their impact into the future.
Rixen et al. (2022) Winters are changing: snow effects on Arctic and alpine tundra ecosystems. Arctic Science. https://doi.org/10.1139/AS-2020-0058