Climate change enhances extreme weather. Therefore, periods of drought are more likely to become more frequent. However, trees in a species-rich neighbourhood do not only grow better, but they are also more resistant to drought. This has been discovered by researchers at Leuphana as part of the BEF-China research project funded by the DFG. For six years, scientists studied the growth of around 3400 subtropical trees in one of the world's largest biodiversity experiments. Although drought reduces the productivity and thus also the ability of trees to remove carbon dioxide from the atmosphere, small-scale diversity can significantly reduce the losses. "The finding that interactions between different neighbours promote precisely those in the community that are most sensitive to drought is impressive. Neighbourhood diversity thus acts like a social safety net and explains why species-rich forests can be more resistant to climate change," Fichtner explains. Neighbourhood diversity can improve water availability and uptake during dry periods. For example, some tree species root shallowly and draw moisture from upper soil layers, others root deeper or pump water into upper soil layers. The competition for water is thus less intense in species-rich neighbourhoods than in neighbourhoods of the same species.

The higher the small-scale diversity, the better – this also holds for the whole forest. "How trees interact with each other in the local neighbourhood is important for the functioning of the entire ecosystem," Fichtner explains. Ecology therefore advocates promoting small-scale tree species diversity in the forest, especially in the tropics and subtropics, where trees grow particularly fast. Biodiversity could thus become increasingly important concerning climate change in order to stabilise the ecosystem services of forests. "Ecosystem-based solutions, such as the promotion of species-rich forests, are an important building block for climate protection strategies," says Fichtner.

Dr. Andreas Fichtner ©Leuphana/Patrizia Jäger
Dr. Andreas Fichtner is a research assistant at the Institute of Ecology.