Taller plants on the tundra

Tundra ecosystems, present in northern arctic and alpine regions, lack trees but have an abundance of shrubs, grasses and mosses. 

“Tundra plants grow slowly, trapping carbon below ground,” explains ecologist Isla Myers-Smith of the University of Edinburgh. “As much as two thirds of plant biomass could actually be growing below ground in tundra ecosystems, and it is thought that about one third of the world’s soil carbon is stored underground in northern ecosystems, including the tundra and boreal forest,” she says.

Taller tundra plants could trap more snow in winter, insulating the soil. They can also stick above the snowpack in spring, making the surface darker. A darker surface will not reflect the sun’s heat the way white snow and ice do, which could warm this cold ecosystem, accelerating vegetation change, permafrost thaw and potentially altering carbon storage, explains Myers-Smith.

The researchers assembled three-decades-worth of more than 50,000 measured trait observations of tundra plants in 117 tundra locations. They analysed their data using statistical models to account for the hierarchy in trait changes between individual plants and the plant community as a whole, as well as the effects of space and time. 

Their results showed that plant height was the only trait of several key traits that was increasing over time. This is partly due to rising numbers of taller plants in tundra plant communities, but mostly due to the migration of taller species into plots that were monitored over decades. There was no indication that numbers of shorter species are decreasing or disappearing from the monitored plant communities.

“If taller plants continue to spread at the current rate, the plant community height could increase by 20 to 60% by the end of the century,” says ecologist and lead author Anne Bjorkman from the Senckenberg Biodiversity and Climate Research Centre (BiK-F), Denmark.

“We are still not certain if more carbon will be released as tundra ecosystems warm and vegetation communities change. This is one of the priority areas for future research,” says Myers-Smith. “Understanding how tundra ecosystems have been changing will help us make better predictions of future change as the climate warms and what the impacts might be for the planet as a whole,” she adds.

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