The good and bad of winter warming

Milder winters should be good, at least for now. A study on a subantarctic island has found that climate warming, especially during winter, benefits tree establishment. What researchers did not expect to find was that winter warming negatively affects summer growth. Winter temperatures are expected to have a negligible effect on plants as most plants at high elevations or latitudes are dormant during winter or covered in snow. Snow cover on subantarctic islands, however, is short-lived. With declining winter snowpacks globally, conditions on subantarctic islands provide a potential window into the future for areas currently covered in snow during the winter months.

Using growth and establishment records for Dracophyllum trees and 60 years of climate data, scientists from the University of Washington, USA and Landcare Research, New Zealand show that winter, not summer, climate is associated with tree establishment and growth.

According to Dr. Harsch, "we don't see the negative effect of winters on growth when temperatures are cold. We see this effect when there is a wide range in winter temperatures." The exact mechanism is not known at this point but scientists believe it has to do with metabolic stress. The effects of winter warming on plants have been largely overlooked. However, as snowpacks decline with climate warming, plants will be exposed more often to winter conditions.

The findings, published April 1st in PLOS ONE, suggest that as winters warm, milder winters will promote establishment. Further warming, however, may lead to decreased growth rates, even in regions where plants are currently protected from harsh winter conditions by snow cover. The negative effects of winter warming are expected to be most pronounced in maritime and oceanic regions.

More information:
Paper: dx.plos.org/10.1371/journal.pone.0093241

Provided by University of Washington