NEWS The warmer climate that is expected over the next 80 years could lead to major disruptions in ecosystems of high mountain landscapes, for example by altered balance between nitrogen and phosphorus in the soil.
The results in a new study are presented by an international team of researchers led by SLU in Nature. Maja Sundqvist, active researcher in the Climate Impact Research Centre (CIRC), Umeå University, participated in the study.
– Mountain ecosystems are so-called 'hot spots' of biodiversity. Our results indicate that current and any future migration of plant species up the mountain slopes, as a response to increased global temperatures, could lead to a ground vegetation with higher amount of nutrients in leaves and potentially increasing nutrient cycles, says Maja Sundqvist, Assistant professor at the Department of Ecology and Environmental Sciences, Umeå University.
Mountain ecosystems worldwide are highly vulnerable to human-induced global warming. This is characterized both by the movement of tree lines, and by changes in other vegetation that are independent of tree responses. While many experiments have been performed to try to understand how global warming affects mountain ecosystems, climate-driven effects occur over a much longer time frame than the duration of any existing experiment, and most experiments are not well suited to study responses of large, long lived plants such as trees. Therefore, our knowledge of how long-term warming may affect mountain ecosystems globally remains limited.
An article published today in the prestigious international journal Nature, coordinated by SLU postdoctoral researcher Jordan Mayor and professor David Wardle (both with the Department of Forest Ecology and Management), and coauthored by Dr Maja Sundqvist, Umeå University and researchers in eight other institutions including the Universities of Vermont, Manchester and Grenoble, sheds new light on how climate warming may affect mountain ecosystems globally.
Instead of utilizing short term experiments, the researchers studied elevational gradients in mountains both above and below the alpine tree line. Elevation serves as a surrogate for warming, because temperature declines with elevation and, as a consequence of warming, any particular elevation is expected to experience the same temperature as that of an elevation that is 300 meters lower in 80 years’ time. To test for the generality of their findings, they utilized elevational gradients in seven distinct temperate regions of the world: Hokkaido, central Europe, New Zealand, eastern Australia, Colorado, British Columbia and Patagonia.
They found recurrent responses of ecosystem properties to elevation across the seven regions. Decreasing elevation consistently increased the availability of soil nitrogen for plant growth, meaning that warming will be expected to improve plant nitrogen nutrition. However, they also found that plant phosphorus availability was not controlled by elevation in the same way as nitrogen, and consequently that the balance of nitrogen to phosphorus availability was very similar across the seven regions at high elevations, but diverged greatly across the regions at low elevation. This means that the balance of nitrogen and phosphorus availability is constrained by low temperatures at high elevations, while at low elevations and as temperatures become warmer, regional factors and differences between regions become more important.
When the researchers explored the mechanisms that underpinned the consistent responses to elevation across the seven regions they found that increasing temperature and its consequences for plant nutrition were linked to changes in the amount of organic matter in the soil, the quality of this organic matter, and the microbial community that occurred with decreasing elevation. These findings reveal some remarkably comparable responses to increasing temperature across contrasting regions around the world. They also found these changes to at least partly be independent of any effect of the alpine tree line, meaning that effects of warming on ecosystem properties will occur irrespective of whatever tree migration that will occur due to higher temperatures.
Much remains unknown about how human-driven climate change and global warming will affect the Earth’s ecosystems in the long term and over large spatial scales. Through a simple use of a natural experiment (i.e., elevational gradients distributed around the world) the researchers were able to provide evidence that temperature changes of the magnitude expected to occur over the next 80 years have the potential to greatly disrupt the functional properties of the Earth’s mountain ecosystems and result in increased disequilibrium in both above- and below-ground ecosystem components.
The Climate Impacts Research Centre (CIRC) conducts research, education, and outreach with focus on terrestrial and aquatic ecosystems in Arctic and alpine environments. The aim is to integrate new knowledge in ecology and biogeochemistry to get a better understanding of current conditions and making projections for the future. The operations are based in the Abisko Scientific Research Station, 200 km north of the Arctic Circle in Sweden (68.35° N, 18.82° E).
Mayor, R. et al: Elevation alters ecosystem properties across temperate treelines globally. Nature. 2017
www.nature.com/nature/journal/vaop/ncurrent/full/nature21027.html
Maja Sundqvist, Deparment of Ecology and Environmental Sciences, CIRCTelephone: +46(0)70-359 07 21
Email: maja.sundqvist@umu.se
Editor: Ingrid Söderbergh