Collaborative research involving scientists from Trinity College Dublin has shown that forests are able to limit the effect of climate change on the plants in their communities, such that different species are favoured in these habitats rather than in more open areas.

The work, recently published in the leading international journal Proceedings of the National Academy of Sciences, should have implications for conservation efforts. Trinity scientists Associate Professor and Head of Botany, Daniel Kelly, Professor in Quaternary Ecology, Fraser Mitchell, and Researcher, Miles Newman, worked with others in Europe and the US in the extensive collaborative project.

They compiled more than 1400 vegetation surveys from European and North American ancient deciduous forests, which comprise trees that lose their leaves with the seasons. These historical records showed that 'warm-adapted' species, such as common ivy, have become considerably more common than they were 35 years ago, but under the forest canopy cooler temperatures are limiting their spread. The scientists behind the discovery recommend preserving forests as safe refuges for 'cold-adapted' plants that are struggling in a warmer world.

Forest management practices have changed considerably since World War II, and many temperate forests have become denser. However, due to increasing demands for wood, among other reasons, forests are being harvested and tree canopies opened up. This scenario could see the warm-adapted plant species spread their ranges even further.

The Trinity collaborators warn that this could have real implications for plant diversity in Ireland. Professor Mitchell said: "It is interesting to note that the Irish data contributed to this international investigation provide the strongest support for the overall conclusion that dense forest canopies dampened the impact of global warming.

"This implies that the flora in Irish woodland is most vulnerable to the impacts of global warming if the tree canopy cover is not maintained. The principal threat to maintaining canopy cover is the inability of trees to regenerate due to high grazing pressure and this has been identified as a significant issue in woodland across the state."

Researcher Miles Newman added: "If mature canopy cover is not maintained or promoted, we are likely to lose cold-adapted woodland plant species in the future. One of the greatest threats to tree canopy regeneration in Ireland is high levels of deer grazing in woodland areas."

The United Nations recently published a climate report that again confirmed the warming of global climate, which has many effects on plants and animals. In the Alps, for example, many species are found living considerably higher in the mountains than they were a few decades ago, because rising temperatures have enabled them to spread into previously inaccessible environments. This same pattern is also seen in lowland forests.

More information: "Microclimate moderates plant responses to macroclimate warming." Pieter De Frenne, Francisco Rodríguez-Sánchez, David Anthony Coomes, Lander Baeten, Gorik Verstraeten, Mark Vellend, Markus Bernhardt-Römermann, Carissa D. Brown, Jörg Brunet, Johnny Cornelis, et al. PNAS 2013 110 (46) 18561-18565; published ahead of print October 28, 2013. Journal information: Proceedings of the National Academy of Sciences "Microclimate moderates plant responses to macroclimate warming." Pieter De Frenne, Francisco Rodríguez-Sánchez, David Anthony Coomes, Lander Baeten, Gorik Verstraeten, Mark Vellend, Markus Bernhardt-Römermann, Carissa D. Brown, Jörg Brunet, Johnny Cornelis, et al.2013 110 (46) 18561-18565; published ahead of print October 28, 2013. www.pnas.org/content/110/46/18561.full.pdf+html