Will photosynthetic gain of boreal evergreen conifers increase in response to a potentially longer growing season?

[Extract] Temperature and light are the main drivers of phenology in boreal evergreen conifers, determining the length of the photosynthetically active season (growing season length). However, temperaturelight-interactions and their effect on the physiological processes underlying the phenology of evergreen conifer trees are yet not understood (Lloyd et al 2002). Climate change and the anticipated increase in northern latitude air temperature are likely to increase the length of the growing season, due to generally warmer temperatures in spring and autumn. Despite this, only few experiments have isolated the effects of temperature for this scenario on trees and forests. Plants often respond positively to increased temperatures but we need to understand how close the current climate is to the optimum (Saxe et al 2001). Will temperatures rise outside the range in which trees can behave optimally? Will trees exploit the growing season only incompletely due to e.g., disruption of regulatory mechanisms, and increased frost damage? In this presentation we give two examples of how increased temperature can effect autumn and spring processes in boreal Scots pine