Researchers from Umeå University, Germany and Finland discover novel mechanism clarifying the slow nutrient cycling in Arctic soils. Absence of earthworms can explain why Arctic plants are starving for nitrogen. The study was published 14.4.2020 in the prestigious Nature Communications.

Nutrients release from plant litter and nutrient
turnover in Arctic soils proceeds very slowly and largely constrains tundra plant
growth. The fact that nitrogen limitation is so widespread in the Arctic has for a
long time been interpreted to result from the cold climate that slows down the
activities of decomposers.

A new study from the Climate Impacts
Research Centre at Umeå University in Sweden has identified a previously
underestimated mechanism behind the current nitrogen limitation: the release of
nitrogen from the Arctic soil to plants is largely limited by the lack of larger
soil animals, such as earthworms. These animals can cut plant litter into smaller
fragments and translocate them deeper into the soil where they are more easily
processed by other decomposers. This greatly accelerates the decomposition rate and
enhances the release of nitrogen from the soil.

“That you can
increase the release of nitrogen from decomposing soil without increasing the
temperature is conceptually important as it change the way we predict future
environmental change on the tundra”, says Dr. Jonatan
Klaminder, Umeå University, main author of the study.

The study shows that if new earthworm species are added to the Arctic soil,
the breakdown of organic matter is enhanced and the plant nitrogen uptake increases
dramatically with consequences on their growth.

The authors
observed that some plants doubled their shoot and roots length. The observed effects
on the entire plant community in terms of nitrogen uptake and plant production were
greater than previously observed effects to climate warming, fertilization and
grazing.

“Gardeners know the beneficial effects of earthworms for
soil nutrients and plant growth but, in intrinsically earthworm-free tundra, these
effects should be considered critically as they can irreversibly change the
ecosystem”, says Dr. Maria Väisänen, University of
Lapland, co-authors of the study.

The study indicates human
activities known for introducing invasive soil fauna, such as farming, gardening and
live bait fishing, needs to be considered in addition to climate change when
predicting how tundra ecosystems will change during the coming century.
 
Original
article:
Blume-Werry, G., Krab, E.J., Olofsson, J.,
Sundqvist, M.K., Maria Väisänen, M., Klaminder, J.: Invasive earthworms
unlock arctic plant nitrogen limitation. https://rdcu.be/b3y6p
DOI
10.1038/s41467-020-15568-3

More
information:

Postdoctoral Researcher Maria
Väisänen
Arctic centre, University of Lapland
Ecology and
genetics research unit, University of Oulu
maria.vaisanen(at)ulapland.fi, +358 40 541 6146

 

Photo: Gesche Blume-Werry
Caption
Earthworms in the midst of tundra meadow vegetation