Monocultures of some of the UK’s most economically important conifers may be more resilient to spring drought than mixed-species forests, according to new research by the University of Stirling

Although mixed-species forests can be more productive and provide a wider range of social, environmental and economic benefits than those containing a single species, they may not be as resilient to drought, researchers found.

Using a long-term experimental forest in Ardross, near Inverness in Scotland, they measured the impact of a spring drought in 2012 on monocultures of two species – Sitka spruce and Scots pine – compared to mixtures of the same two species growing together in different proportions.

Scots pine and Sitka spruce are two of the most economically important timber species in the UK, collectively making up 68% of all the UK’s coniferous forest area, with Sitka spruce alone comprising 51%.

PhD researcher Tom Ovenden, of the Department of Biological and Environmental Sciences, who led the study, said: “As expected, we found evidence that Scots pine was more resistant to drought than Sitka spruce.

“However, to our surprise, monocultures of both species appeared to be more resilient to spring drought than any of the mixtures of the two species that we considered.

“As we rapidly try to adapt our forests to deal with the challenges of a changing climate, it’s important that decisions on how best to achieve this are based on robust scientific evidence.

“This work is important because it demonstrates that simply adding more tree species to a forest does not automatically increase its resilience.

“Instead, the existence of any beneficial effects of species mixture likely depends on which species are mixed, their characteristics and how they interact.

“Understanding how to effectively increase forest resilience is important, as the ability of forests to sequester carbon, provide habitat for a range of species and to continue to deliver a range of ecosystems services is dependent on them being robust to climate change.”