Assessment of the impact of climate change on the growth of Sitka spruce in Scotland

A regression model developed to predict the general yield class (GYC, maximum mean annual volume increment) of Sitka spruce (Picea sitchensis (Bong.) Carriere) from a range of site factors has been used to assess the potential impact of climate warming on the growth of Sitka spruce in Scotland. The model was interfaced with a geographic information system to predict and map the GYC of Sitka spruce across Scotland under a number of climate change scenarios. GYC was predicted to increase by 2.8 m(3) . ha(-1). year(-1) per degrees C rise in temperature when a uniform temperature increase was assumed during the year. A more likely assumption is a greater warming during winter months, and under such a scenario the Increase in mean GYC was predicted to be 2.4 m(3) . ha(-1). year(-1) .degrees C-1 because of a negative correlation between growth rate and mean winter temperature, When assessed in terms oi land area capable of supporting a GYC greater than 18 m(3) . ha(-1). year(-1) (a value likely to provide an internal rate of return of approximately 6%), this area was predicted to almost double within the next 20 years with a similar increase occurring during the subsequent 40 years.