Research conducted by scientists from the Tokyo University of Agriculture and Technology and the Forestry and Forest Products Research Institute suggests that Asiatic black bears may play a role in helping wild cherry trees adapt to changing climate conditions.

The study found that bears consuming wild cherries later deposit seeds at higher elevations through their droppings. The movement of seeds to cooler locations may help cherry trees respond to rising temperatures.

“Plants are facing expanding challenges from the adverse impact of global warming, such as inhibited growth,” said Shinsuke Koike, an ecological professor at the graduate school of the Tokyo University of Agriculture and Technology. “This means that they need to relocate to far elevated locations with cooler readings.”

© Forestry and Forest Products Research Institute

The research was conducted at three mountainous sites: Okutama in Tokyo and other parts of the Kanto Mountains, Nikko in Tochigi Prefecture within the Ashio Mountains, and Kita-Ibaraki in Ibaraki Prefecture on the Abukuma Plateau.

Researchers collected and analysed droppings from mammals and birds to examine seed dispersal patterns for two cherry varieties, Korean mountain cherry, which fruits in early summer, and Japanese bird cherry, which fruits from late summer to early autumn.

The study found that Asiatic black bears accounted for 44 to 80 per cent of Korean mountain cherry seed dispersal around their habitats in the Kanto and Ashio mountain regions. For Japanese bird cherry, bears accounted for 54 to 67 per cent of seed dispersal.

Analysis of oxygen isotope ratios and other factors indicated that many of the seeds had been transported to higher elevations.

The situation differed in the Kita-Ibaraki area of the Abukuma Plateau, where Asiatic black bears are no longer present. There, martens and raccoon dogs are now the main seed dispersers, and the number of seeds being transported has declined.

According to the researchers, previous studies have shown that birds typically disperse only 10 to 30 per cent of seeds. Koike noted that bears consume nearly 100 fruit species and may travel up to 20 kilometres before depositing seeds, while birds often transport seeds only a few hundred metres.

“It remains, however, unclear in some respects why bears are apt to bring seeds to higher locations,” he said.

The findings suggest that Asiatic black bears contribute to the dispersal of wild cherry seeds across mountainous landscapes, including movement into cooler, higher-altitude environments.

Source: The Asahi Shimbun