Alpine plant decline linked to smaller rhizomes and shorter fine roots

Alpine ecosystems are especially vulnerable to climate change, and many of them are already experiencing rapid warming that is associated with noticeable shifts in alpine vegetation.

After previous research noted significant changes in the make-up of alpine meadow plant species in the Taisetsu mountains of northern Japan over four decades, a research team including Haruka Kobayashi (MSc student at the time of the study), Associate Professor Makoto Kobayashi and Associate Professor Gaku Kudo at Hokkaido University investigated which traits might influence a plant's chance of survival in a changing climate.

"Studies on the relationships between plant performance and functional traits have focused mainly on aboveground traits, and less attention has been given to belowground traits," Professor Kobayashi says.

In their new study, published in the journal Alpine Botany, the team studied 12 species of broad-leaved herbs growing in an alpine meadow in Goshikigahara in the Taisetsu mountains. Four of them are known to have become less common in the meadow over the previous 40 years, while the other eight have become more common.

The aim was to comprehensively explore whether the increasing and decreasing species have different functional traits, such as leaves, roots and rhizomes.

The researchers found that the herbs that had increased in number across the meadow tended to have larger rhizomes (horizontal stems that send out roots), and longer and thinner finer root systems than those that had decreased in number.

"Species with larger rhizomes may be more successful at persisting by mediating environmental stress through the use of stored and transferred resources from their parent plants. Also, longer fine roots enable plants to acquire more belowground resources such as water," said Haruka Kobayashi, the first author of the study.

Previous studies by the laboratory of Professor Kudo have reported that, in the Taisetsu mountains, earlier snowmelt caused by climate change has led to the drier soil conditions, resulting in changes in vegetation. "Decreased species had smaller rhizomes and shorter fine roots. These species may be more vulnerable to drought stress," said Professor Kobayashi.

However, the study did not find any clear evidence that above-ground traits, such as leaf characteristics, differed significantly between the increasing and decreasing herb species.

"This means that belowground traits are a crucial component predicting the changes in species diversity of alpine vegetation under global warming," Professor Kobayashi concluded.