Environmental variables driving species composition in Subarctic springs in the face of climate change

Prepared by Tara K. Miller, Einar Heegaard, Kristian Hassel & Jutta Kapfer

Springs are important ecosystems to support biodiversity. They are fed by groundwater and are critical for maintaining high biodiversity because of the specific and stable habitat conditions they provide: high water quality, consistent temperatures, and low seasonal variability. These factors result in a distinct species composition (i.e. which species are present together) and higher species diversity compared to surrounding habitats.

This high biodiversity makes springs a critical ecosystem to study. Springs found on mountains depend on the snow conditions above the springs. The snow conditions are expected to vary from year to year, as precipitation and temperature vary, making alpine and subalpine springs particularly vulnerable to climate change.

Despite being common and occurring all over the Norwegian mainland, springs are – as in many other countries in the world – vastly understudied, and we have limited knowledge about their biodiversity and how it is linked with environmental conditions.

We expect that the species composition of plant communities in springs will change with climate change. In order to measure the extent of the effects of climate change on these communities and to predict future risk, it is important to study which species are currently present in springs and which conditions support the presence of different species. We recorded which species were present at 49 spring sites in northern Norway. We also recorded the conditions at the springs, including water quality conditions (water temperature, pH, and the pace of the water flowing from the spring), climatic conditions (air temperature and precipitation), and the spatial location of the spring (altitude and geographical coordinates).

We found that both climatic and water quality conditions were important for determining the species composition in springs. Altitude was also important in determining where species were present. Therefore, altitude may be a limiting factor for plant species in adapting to climate change. For example, if a species is already located at the highest-altitude spring location or if there are no suitable spring sites located at nearby higher altitudes, it may be unable to disperse and migrate to a new, suitable habitat.

Our research gives us a new understanding of the conditions that are important for supporting the presence of different species in Subarctic springs.

This is a plain language summary for the paper of Miller et al. published in the Journal of Vegetation Science (https://doi.org/10.1111/jvs.12955).