Tree and forest functioning in response to global warming

Although trees have responded to global warming in the past - to temperatur es higher than they are now - the rate of change predicted in the 21st cent ury is likely to be unprecedented. Greenhouse gas emissions could cause a 3 -6 degreesC increase in mean land surface temperature at high and temperate latitudes. Despite this, few experiments have isolated the effects of temp erature for this scenario on trees and forests. This review focuses on tree and forest responses at boreal and temperate latitudes, ranging from the c ellular to the ecosystem level. Adaptation to varying temperatures revolves around the trade-off between utilizing the full growing season and minimiz ing frost damage through proper timing of hardening in autumn and dehardeni ng in spring. But the evolutionary change in these traits must be sufficien tly rapid to compensate for the temperature changes. Many species have a po sitive response to increased temperature - but how close are we to the opti ma? Management is critical for a positive response of forest growth to a wa rmer climate, and selection of the best species for the new conditions will be of vital importance.