January 11, 2013
The Nature Communications study, conducted by researchers at the Swedish University of Agricultural Sciences and Future Forests, looked six different ecosystem services afforded by forests (tree growth, carbon storage, berry production, food for wildlife, occurrence of dead wood, and biological diversity) as well as tree growth rates. It found that "all six services were positively related to the number of tree species" suggesting that mixed forests can potentially offer a broader array of forest products.
A press release from the Swedish University of Agricultural Sciences explains:
Different trees contribute to different services. For example, the amount of spruce is related to high tree growth and the amount of pine to berry production, while carbon storage was found in plots with more birch. In order to attain more of all services, forestry may thus need to make use of different tree species.
“Many people have suggested that high diversity of tree species has a favorable impact on processes in the ecosystem, but until now this connection has primarily been studied in terms of one process or ecosystem service at a time,” Gamfeldt said in a statement.
The authors say the results are consistent with other studies in temperate and boreal regions.
While the findings may seem like common sense to ecologists, diversity isn't a principle that is widely embraced in Sweden's forestry sector. According to Swedish National Forest Inventory, only about 7.5 percent of Sweden's productive forest land has mixed forests.
“Our findings show that both forestry and nature conservation stand to gain by promoting a greater variety of tree types, thereby providing more diverse ecosystem services,” added Jan Bengtsson of the Swedish University of Agricultural Sciences.
Other research has shown that natural forest ecosystems are typically characterized by much higher levels of biodiversity — boosting forest resilience to outside stress as well as fostering a wider array of income streams — relative to monoculture plantations.