Feature Plant
What’s going on under the snow?
Snow covered plants in the Rocky Mountains of Alberta
Photo by L. Allen
Snow can act as an insulating blanket, keeping the plants under it warm and protecting them from frost damage. But what are the plants doing under that blanket?
Turns out, enough of the sun’s radiation can penetrate the snow that plants know the time of day, time of year, and when to initiate appropriate life phases. Even under snow depths of up to 2m, the radiation levels are strong enough to initiate sprouting and seed germination.
Korner (1999) was looking at the strategies alpine plants use to survive under snow, and divided them into six general groups.
- Some maintain green structures such as overwintering leaves or photosynthetic bark. These continue to be fully photosynthetic thru winter. Mosses and lichens can actually have a net carbon gain under the snow (depending on factors like depth and density of the snow).
- Some, like bog cranberry or lingonberry (Vaccinium vitis-idaea), retain green structures, but deactivate photosynthesis. Once snow-free, it takes about two weeks to for these plants to regain full photosynthetic capacity.
- Then there is the more conventional strategy of going dormant, with new green leaf emergence occurring after snow melt.
- But some species initiate leaf expansion while still under the snow – so they can commence greening and photosynthetic activation as soon as they are in the open. These tend to be the spring ephemerals like glacier lilies (Erythronium grandiflorum).
- Some of the fast-growing taller species like geranium actually start expansion as soon as they emerge from the snow but delay greening.
- And lastly there are the annuals, with seeds that germinate at snow melt. The longer the snow cover lasts the less well this strategy works. It is rare for an alpine plant to be an annual – takes too long to germinate, grow, flower and set seed again.
So what are the plants doing under that blanket? It seems that some are napping, some are sleeping deeply, and some are just waiting around for spring.
References: Korner, C. 1999. Alpine plant life. Functional plant ecology of high mountain ecosystems. Springer Heidelberg. 338 pp + colour plates.