The alpine zone supports some of Scotland’s most natural habitats. Complex topography interacts with snow cover and climate to create gradients in water availability and temperature, resulting in a mosaic of plant communities variously dominated by dwarf-shrubs, grasses, or mosses.
Above and below-ground biodiversity and ecosystem functioning are closely linked, and we expect above-ground variability to be reflected below-ground, but our knowledge of alpine soil biodiversity and functioning is poor. As alpine systems are increasingly affected by climate change, we need to better understand how these complex systems work, to enable us to predict the impacts on biodiversity and the ecosystem services they provide.
Stage
Work in ProgressDirectory of Expertise
Purpose
The alpine zone (the area above the tree line) comprises a complex mosaic of plant communities resulting from variability in key factors such as water availability, snow-lie duration, temperature, and wind speed. Alpine plant communities vary markedly in their functional composition (e.g., dwarf shrub heaths vs grasslands vs moss-dominated communities) and this variability is likely to be reflected below-ground, in terms of soil biodiversity and functional attributes (carbon stock, nutrient stocks, nutrient cycling, and decomposition). However, to date we have not explored the variability in alpine soils at fine scales and our knowledge of the variation in soil biodiversity and function across mosaics of alpine plant communities is very limited.
Figure: The Ben Avon plateau in the Cairngorm mountains showing the mosaic of snowbed, grassland, dwarf-shrub heath, and moss-dominated plant communities.
(Photograph by Dr Andrea Britton)
Scotland’s climate is changing. The last 40 years have seen significant changes in seasonal air temperatures, amounts of precipitation, and the timing and duration of snow cover. Alpine habitats are also subjected to nitrogen pollution in rainfall and impacts arising from human land use. These, and future changes, are altering the composition and distribution of plant communities across the landscape. Plant community composition and soil biodiversity are tightly linked so, as plant distributions change, we expect this to impact belowground biodiversity, soil function and ecosystem services. The purpose of this research is to develop a greater understanding of soil biodiversity and function across alpine vegetation mosaics to enable us to better predict these impacts.
Results
The Ben Avon plateau, lying within the Cairngorms National Park, comprises the largest contiguous area of alpine vegetation in the UK.
We sampled vegetation and soils at 99 locations distributed across the seven main vegetation types on the mountain, covering 650m to 1171m elevation. At each location we described the plant community and took soil samples from which we extracted DNA to characterize soil biodiversity. Recent advances in DNA sequencing technology allow us to detect the full diversity of fungi, bacteria and other microorganisms present in soil by extracting and sequencing their DNA. Detecting soil organisms would be impossible on this scale using traditional observational methods, and these techniques are revolutionizing our understanding of below ground biodiversity. We also measured carbon and nutrient stocks above- and below-ground and made assessments of decomposition rates, plant nutrient availability, soil temperature, and moisture.
Figure (L-R): Digging and describing a soil profile pit to measure carbon and nutrient stocks, a sampling plot in snowbed vegetation, sampling vegetation and soil in Racomitrium heath.
(Photographs by Dr Andrea Britton)
The data we have gathered will be used to develop a detailed understanding of the relationships between above and below ground biodiversity, carbon, nutrient stocks and cycling, and environmental conditions. Already they are revealing a fascinating insight into the biodiversity and functioning of Scotland’s alpine soils.
We found that alpine soils support a high biodiversity, with over 27,000 taxa (species or broader groups) of bacteria, fungi and microorganisms detected. These included fungi previously recorded in Antarctica and species previously considered to be very rare.
Each of the seven vegetation types supported distinctive soil communities. Snowbed communities and summit fell-field supported particularly high soil biodiversity with many unique species, while diversity was lower in lower elevation habitats (see example of soil fungi below).
In contrast, soil carbon stocks declined as elevation increased (see figure) and were lowest in the moss-dominated snowbed which is typically snow-covered for more than 200 days per year. Very large carbon stocks were found in subalpine heaths occupying the lower, shallower slopes of the mountain.
Figure: Biodiversity and carbon stocks in the soils associated with the seven most extensive vegetation types on the Ben Avon plateau. The left panel shows the number of fungi detected in each sampling plot and the right panel shows the amount of carbon stored in the top 1m of the soil profile. The horizontal line within each coloured box shows the average value and the height of the box and ‘tails’ indicate the range.
These initial results show how biodiversity and carbon stocks vary across the mountain and highlight how the importance of each habitat could be perceived differently when considered from different perspectives; the research will be published when complete. Our next steps will be to investigate how the distribution of biodiversity and nutrient stocks is related to environmental factors such as temperature and moisture, so that we are better able to predict what the impacts of climate change might be in these iconic habitats.
Benefits
Our study on the Ben Avon plateau is the first to examine in detail soil biodiversity and functioning in one of the last near-natural habitats in the UK. The work has given novel and unique insights into the distinctive and hugely diverse communities which exist in Scottish alpine ecosystems – and this was only from one mountain. There are 282 mountains over 3000ft in Scotland, each of which is likely to harbor unique components of this Scottish natural capital. Our results also reveal a much more detailed picture of the distribution of carbon stocks across alpine landscapes and the key factors influencing this.
Given the ongoing changes in alpine plant distributions in response to climate and other global change factors, our data will help to develop our understanding of the potential consequences of these changes for soil biodiversity, functioning and ecosystem services. Our study also highlights the importance of key habitats such as snowbeds which support many unique species despite their limited area. As snow cover duration reduces with a warming climate, such habitats, and the species they support, are at risk of being lost before we have fully explored them.
Project Partners
The James Hutton Institute