Global climate change scenarios predict that high latitude areas will become wetter and warmer, especially during autumn, winter and spring. Although air temperatures will undoubtedly increase, changes in soil temperatures might not follow the same trend as they depend on the insulating snow cover.
The state of the snow cover depends, correspondingly, on weather conditions. More frequent warm spells, rain-on-snow events and freeze-thaw cycles may cause either melting of snow, compaction of snow, formation of ice layers within the snowpack, or ground ice encasement. Because solid ice is nearly impervious to respiratory gases, continuing soil microbial activity under the snowpack may lead to hypoxia and anoxia. This phenomenon could change completely the prevailing winter conditions in boreal ecosystems in which plants and soil micro-organisms are adapted for overwintering under aerobic conditions.
In addition, the lower insulating properties of compacted snow and ice lead to deeper soil frosts. In addition, the slow-melting ice layers delay soil thawing in the spring. More frequent warm spells have the potential to transiently stimulate plant metabolism which might lead either to higher desiccation stress in case of frozen soil, or to rapid depletion of carbon and nitrogen pools in case of anaerobic respiration under ice layers. Although less frequently studied but most likely as important as changing conditions during the growing season, changing winter conditions are thus expected to affect the productivity and biodiversity of the boreal forest.
Hard work on the snow field
This fundamental research question of the effects of winter climate change on forest regeneration and productivity constitutes the basis of an Academy-funded project “Winter in changing climate: effects of snow conditions on plants, soil and their interactions in the boreal forest”, ongoing until 2017 in Luke Rovaniemi. A large field experiment has been set up in Rovaniemi area with different snow-manipulation treatments of 10 blocks and 5 treatments with both Scots pine and Norway spruce seedlings planted.
The success of this large field experiment depends on a lot on the care taken. Last winter, the snow manipulation included, for example, snow melting by artificial rain-on-snow (in reality: manual watering of 80m2 with more than 1500 l of water), manual snow compaction several times during the winter (80m2 each time), or sudden setting up of rain shelters in case of forecasted natural rain-on-snow events. Soil gas samples have also been collected weekly and analyzed in the laboratory.
As our interest was to study the carbon and nitrogen pools before spring regrowth, one practical challenge in the field experiment was the root and soil sampling in frozen soil. Now that the second year of this snow-manipulation experiment is ending, we have just finished our laborious spring sampling. We are also getting results: many analyses are still running but preliminary results suggest a detrimental effect of snow modification on winter survival and height growth of both Scots pine and Norway spruce outplanted seedlings.
Technical staff support is vital
However, my aim in this blog is for sure not the dissemination of (unpublished) scientific results, but I would like to illustrate how essential the technical support from Luke’s staff is to forest research. This field experiment could definitely not have been set up, nor maintained and the sampling not been done without the help of many forest engineers working at Rovaniemi. The next step of the research goes on in sample analyses; several types of analyses have been done and will be done in Luke’s laboratory by Luke’s staff. So globally, this project has involved a lot of technical help from our institute.
Running this kind of field experiments to answer important research questions will not be practically as easy in the future due to staff reduction. The question arises: how to include field experiments in future research projects? Consequently and more concretely another question requires an answer: how should budgets be planned in future funding applications? This is essential information that we researchers need now for projects that will be carried out in the coming years.
Video: Taking soil samples for forest research in Rovaniemi, in the middle of the winter.