Taller plant species are taking over in the Arctic

Until now, the tundra was mainly the domain of low-growing plants, but larger plant species, especially shrubs, are slowly taking over this cold environment as a result of a rise in temperature. It also seems that taller tundra plants could accelerate climate change.

10/03/2018 | 11:26 AM

An international research team of ecologists, among who is Hans Cornelissen, published these outcomes on September 26 in the journal Nature. The research team collected and analyzed the most comprehensive data set on tundra plants at almost 120 locations in polar and alpine areas. Defying the harsh conditions of the tundra areas, plants huddle close to the ground and often grow only a few centimeters high. But the study based on field data collected by nearly 130 ecologists led by German scientists shows that larger plant species are slowly taking over the tundra area. "The increase in height we saw was not just in a few sites but nearly everywhere," says Anne Bjorkman, lead author of the article.

Shifting of plant species
The researchers identify climate warming as the underlying cause. Temperatures in the Arctic have risen by about 1 degree Celsius in summer and 1.5 degrees in winter over the three decades covered by the study. A detailed analysis showed that not only do individual plants grow taller with warmer temperatures, but that the plant community itself has also shifted. Taller plant species, either from warmer pockets within the tundra or from southern or lower elevation areas, have spread across the tundra. “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 Bjorkman. Surprisingly, the researchers found no evidence that this ‘invasion’ of taller species is not yet leading to a decline in shorter species. The larger plant species do not expel the low-growing plants and the Arctic is becoming ever greener.

Climate change
Arctic regions have long been a focus for climate change research, as the permafrost underlying tundra vegetation contains one-third to half of the world’s soil carbon. When the permafrost thaws, greenhouse gases could thus be released. An increase in taller plants, especially shrubs, could speed up this process as taller plants trap more snow in winter, which insulates the underlying soil and prevents it from freezing quickly and deeply in winter. “Although there are still many uncertainties, taller tundra plants could accelerate climate change, both in the Arctic and for the planet as a whole”, Bjorkman concludes.

Manual for measuring plant functional traits
To measure the plant traits, the researchers of this study followed the standard protocols published by VU researcher Hans Cornelissen as the first author in 2003 as a manual in Australian Journal of Botany and then as a senior author the update in 2013. By following these protocols the measurements could be compared well with each other. The manual has become a classic in plant ecology and both articles have now been cited 2200 times according to The Web of Science.