Abstract/Summary

This Technical Report: 1. Introduces observed and expected effects of rising temperature, elevated CO2 and soil water availability on temperate forests; 2. Outlines current knowledge on impacts of climate change on tree phenology and reproduction; 3. Suggests forest management approaches and options suitable for adapting UK forests to climate change. The key findings of the Technical Report are: 1. Temperature rise in the predicted band of 2-4oC in this century is likely to increase forest productivity in tree populations which are currently not at the southern boundary of species distribution, directly by increasing the rate of CO2 assimilation and indirectly by lengthening the growing season [high confidence]. 2. Elevated CO2 will stimulate forest net primary production, at least in the short term (1-2 decades). Any long-term stimulation is subject to limitation by other factors, notably water availability in the South and East and soil nutrient availability across the UK [high confidence]. 3. Unseasonal low or high soil water availability and high water table levels will negatively affect growth of species not adapted conditions of drought or flooding; this effect is very localised as it is moderated by soil type, topography and artificial drainage [moderate confidence]. 4. Increasing temperature has already resulted in documented shifts in phenology. Potential impacts on productivity can be both positive (longer growing season) and negative (suboptimal release from dormancy) [high confidence]. 5. Elevated CO2 may delay autumnal senescence in broadleaved species, however, there is no indication whether this has an impact on productivity [low confidence]. 6. Rising temperature, elevated CO2 and unseasonal fluctuation of soil water availability are expected to interfere with seed production, particularly with masting events which are important for natural regeneration of forests [moderate confidence]. 7. Higher winter temperature will affect natural regeneration by impacting on seed dormancy status of species and provenances that have a substantial chilling requirements to break seed dormancy [high confidence]. 8. Management plans for UK forests will have to adapt to increased uncertainty and to accommodate a greater variation in site conditions over the rotation, the length of which may become shorter [high confidence].