Forests provide a range of ecosystem goods and services (EGS). However, their ability to continue to provide these EGS under a changing climate remains uncertain. While forest managers are encouraged to consider future climate change impacts in their management plans, the tools to aid in this decision-making process are not always available. Regional environmental differences and species-specific responses to climate need to be explicitly considered. Scotland is currently dominated by open landscapes, however there is strong political motivation to increase the amount of forest cover. The main EGS of interest are timber production, carbon sequestration and forest restoration. To understand which tree species would be most suitable under future climate change, we ran a process-based forest gap model for all of Scotland. We simulated monocultures of the three most popular timber trees (i.e., Sitka spruce (Picea sitchensis), Scots pine (Pinus sylvestris) and Douglas fir (Pseudotsuga menziesii)), as well as one simulation of potential natural vegetation (PNV). We used seven GCM-RCM model chains (three RCP 4.5 and four RCP 8.5) to simulate a range of mild to extreme climate change impacts.
Results/Conclusions
In general, climate change had mostly positive impacts on forest productivity however differences in regional patterns depended on the species. Sitka spruce increased in volume (up to 300 m3 ha-1) in the lowlands, while the highlands mostly remain unsuitable for this species under all climate change scenarios. However, warmer winter temperatures in some lowland areas (e.g., in the south and along the west coast) experienced reduced natural regeneration, due to the chilling requirement not being met. Scots pine, which grows well in most of Scotland under current conditions, would experience a decrease in growth under all climate change scenarios (up to a loss of ~70 m3 ha-1). Douglas fir was simulated to have very high productivity (between 400 to 500 m3 ha-1 in as little time as 40 years) under current conditions. Under all climate change scenarios, the highlands and lowlands become increasingly suitable for Douglas fir. Increased growth and productivity for some species (and in some locations) was found even under the most extreme warming scenarios. Understanding these regionally and species-specific differences will help managers prepare for an uncertain future.