Nav: Home

With climate change shrubs and trees expand northwards in the Subarctic

March 15, 2017

CLIMATE CHANGE Shrubs expand in the tundra in northern Scandinavia. And it is known that fixation of nitrogen from the air is in the tundra to a high degree performed by cyanobacteria associated with mosses. Also enhanced nitrogen fixation stimulates plant growth. New research shows that as taller shrubs expand into the tundra, nutrients in their leaf litter will either promote or reduce the nitrogen fixation, depending upon which shrub species that will dominate. The scientific results have recently been shown by scientists Kathrin Rousk and Anders Michelsen from Center for Permafrost and Department of Biology at University of Copenhagen, and is now published in the widely recognized scientific journal Global Change Biology.

Mosses in subarctic tundra are colonized by bacteria that fix atmospheric nitrogen (N2), and together, they can contribute 50% to total ecosystem N input. Despite this key role, the effects of climate warming and increased litter input as a result of shrub expansion on N2 fixation in mosses are ambiguous.

- Assistant professor Kathrin Rousk, Department of Biology, explains, "to aid in predicting the role of moss-associated N2 fixation in a warmer, future climate, we quantified N2 fixation throughout the snow-free period in subarctic tundra. We used data from a field experiment in Northern Sweden, in which climate change was simulated with open top chambers to increase the air and soil temperature, and with addition of plant litter from willow and birch-shrubs.

The results show that N2 fixation was highest in the warmed and in the birch litter addition plots (around 3 kg N ha-1 yr-1), while the willow litter additions lead to decreased N2 fixation rates (less than 2 kg N ha-1 yr-1)

Field experiment in tundra vegetation in Northern Sweden. Open top chambers simulate future warming of soil and plants caused by climate change, and leaf litter is added to simulate enhanced litterfall caused by expansion of birch trees and willow shrubs (Photo: Anders Michelsen)

- Kathrin Rousk concludes, 'Warming will lead to increased N2 fixation rates in mosses, while the consequences of further shrub expansion will depend on the dominant shrub invading: the expansion of willow will likely limit the N input via N2 fixation, whereas a predominance of birch shrubs will increase N2 fixation and with that, N supply to the ecosystem".

The amount of N2 that is fixed is important because N is an essential nutrient for plant growth and is available only in limited supply in arctic ecosystems. Nitrogen availability influences how much CO2 plants are able to acquire through photosynthesis, and hence it impacts the carbon balance. Changes in N2 fixation due to global warming will alter N input to arctic ecosystems with significant consequences for plant growth.

Micrograph of moss leaves with insert micrograph of a chain of blue-green algae (cyanobacteria) (red) on a c. 0.1 mm long fragment of a moss leaf (green). The micrographs of the cyanobacteria, which fix free N2 from the air, are taken in a fluorescence microscope with a green filter (200x magnification). Micrographs by Kathrin Rousk
-end-


Faculty of Science - University of Copenhagen

Related Climate Change Articles:

The black forest and climate change
Silver and Douglas firs could replace Norway spruce in the long run due to their greater resistance to droughts.
For some US counties, climate change will be particularly costly
A highly granular assessment of the impacts of climate change on the US economy suggests that each 1°Celsius increase in temperature will cost 1.2 percent of the country's gross domestic product, on average.
Climate change label leads to climate science acceptance
A new Cornell University study finds that labels matter when it comes to acceptance of climate science.
Was that climate change?
A new four-step 'framework' aims to test the contribution of climate change to record-setting extreme weather events.
It's more than just climate change
Accurately modeling climate change and interactive human factors -- including inequality, consumption, and population -- is essential for the effective science-based policies and measures needed to benefit and sustain current and future generations.
Climate change scientists should think more about sex
Climate change can have a different impact on male and female fish, shellfish and other marine animals, with widespread implications for the future of marine life and the production of seafood.
Climate change prompts Alaska fish to change breeding behavior
A new University of Washington study finds that one of Alaska's most abundant freshwater fish species is altering its breeding patterns in response to climate change, which could impact the ecology of northern lakes that already acutely feel the effects of a changing climate.
Uncertainties related to climate engineering limit its use in curbing climate change
Climate engineering refers to the systematic, large-scale modification of the environment using various climate intervention techniques.
Public holds polarized views about climate change and trust in climate scientists
There are gaping divisions in Americans' views across every dimension of the climate debate, including causes and cures for climate change and trust in climate scientists and their research, according to a new Pew Research Center survey.
The psychology behind climate change denial
In a new thesis in psychology, Kirsti Jylhä at Uppsala University has studied the psychology behind climate change denial.

Related Climate Change Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Bias And Perception
How does bias distort our thinking, our listening, our beliefs... and even our search results? How can we fight it? This hour, TED speakers explore ideas about the unconscious biases that shape us. Guests include writer and broadcaster Yassmin Abdel-Magied, climatologist J. Marshall Shepherd, journalist Andreas Ekström, and experimental psychologist Tony Salvador.
Now Playing: Science for the People

#513 Dinosaur Tails
This week: dinosaurs! We're discussing dinosaur tails, bipedalism, paleontology public outreach, dinosaur MOOCs, and other neat dinosaur related things with Dr. Scott Persons from the University of Alberta, who is also the author of the book "Dinosaurs of the Alberta Badlands".