Cold stress is something that many plants have to deal with, whether it’s a permanent threat when growing in the tundra, or an occasional seasonal problem in the relatively mild climate of southern Britain. Frost is one of the most prevalent forms of cold stress, which many plants try to survive by entering dormancy. Plant communities have several strategies for successfully recovering from dormancy such as regenerating from surface-level buds, underground buds, or from seeds dispersed prior to winter.
Ironically, while snow could be considered another type of cold stress that plants have to deal with, it is known in some cases that snow cover can actually protect dormant plants from cold damage by providing insulation from the air. However, less is known about how much this is a benefit to plant groups of different overwintering strategies and how winter snow cover may shape plant communities. To investigate this in a plant community setting, Frederick Lubbe & Hugh Henry in a recent Annals of Botany paper conduct a field experiment in Canada in which they remove snow cover over three consecutive years and examine the effect of this on the plant community.
Lubbe & Henry predict that removing snow cover should reduce overall plant coverage of the field they examine. Their results show that this is indeed the case but the extent of this does vary year-to- year, probably due to differences in the ambient temperature between the years. The effects of snow removal differed between plants of different dormancy strategy. As would perhaps be expected, plant species that maintain dormancy buds near or at the soil surface were most sensitive to snow removal. Plant species with deeper dormancy structures were more successful after snow removal at least initially, but did become less-so over time. This indicates that even plants with deeper dormancy structure benefit from protection given by snow covering. The authors speculate that this is not all simply about temperature – they find that greater soil depths are both warmer than shallower depths, and also undergo fewer recorded freeze-thaw cycles.
In the final year of their experiment, Lubbe & Henry combined snow removal with litter removal. Litter removal was also detrimental to plant coverage, but particularly to seed-overwintering plants, indicating that a cover of litter as well as insulating snow is important from seed recovery from dormancy. The work done by Lubbe & Henry puts into context how snow cover may impact changes in plant community structure in real environments and that it is not a purely detrimental occurrence, but can actually protect the diversity of some plant communities during cold stress. Maybe plants look forward to a snow day as much as we do!