Forests benefiting from the variety of tree species and genetic diversity

Conceptual illustration of the effects of functional diversity (a) and trophic feedbacks on tree productivity (b) and experimental design (c). Credit: eLife (2022). DOI: 10.7554/eLife.78703

According to a study published today in eLife.

The results suggest that the complex interactions between trees and other organisms must be carefully considered when determining the mix of trees in a forest to ensure the maintenance of a functioning ecosystem.

Diversity is essential to healthy ecosystems. Forests made up of a variety of tree species are more productive because they use resources more efficiently. This is because different species fill distinct niches, meaning they have different optimal physical and environmental conditions, such as their terrain, and have different interactions with other species such as predation events, meaning that they are less competitive.

Additionally, having multiple tree species can reduce the negative impacts of herbivores and soil fungi that may compete for tree nutrients. Few studies have examined the role of genetic diversity within each tree species in a forest, but some plant studies suggest that genetic diversity within a species is also beneficial to the ecosystem.

“To better understand the effects of genetic diversity in forests and guide reforestation efforts, we examined how species variety and genetic diversity within species affect forest productivity,” says co-author Ting Tang. principal of the study, a doctoral student at the University of the Chinese Academy of Sciences in Beijing, China.

Tang and his colleagues used data from a long-term experiment on large tree species and genetic diversity in a subtropical forest. Tree species diversity and genetic diversity within species were manipulated to generate four different levels of plant diversity and the team measured five structural and chemical leaf traits that are known to be highly variable and related to tree growth rates. acquisition of resources.

The team’s investigations showed that trees grown in multi-species forests were more productive than those grown in single-species (or monoculture) forests. Forests with four different tree species had less diversity in soil fungi than monoculture forests, reducing the need for trees to compete with fungi for resources. Herbivore pressure was also less than in monoculture forests.

The team did not find a reduction in soil fungal diversity or herbivore pressure in forests that included a tree species with four distinct genetic origins. But forests that had four different tree species — with individual trees from four genetically distinct family groups in each — had beneficial effects on both fungal diversity and herbivore pressure.

“We found that species and genetic diversity promote forest productivity by increasing the ability of trees to maximize resource use while reducing damage from herbivores and competition from soil fungi,” Tang comments.

The results suggest that species and genetic diversity could help reduce the number and variety of tree competitors, for example, by reducing the cost that herbivores place on trees, the costs to trees of producing compounds defensive to deter them or by reducing competition from fungi. for nutrients. They also suggest that trees in more diverse forests can better exploit individual niches.

“Reforestation projects are key to mitigating atmospheric carbon levels and helping countries reap the full ecological and economic benefits of healthy forests,” said Xiaojuan Liu, associate professor at the Chinese Academy’s Institute of Botany. Beijing science. “Our results suggest that scientists conducting reforestation projects should include multiple tree species and genetically diverse individual trees within each species to ensure healthier forests.”