Samples and soils
Of the 765 samples submitted we successfully extracted and sequenced DNA from 761 samples. These included 314 samples from moss heath, 276 from ericaceous shrub heath and 171 from grassland. Sample elevation varied between 560-1283m with an average of 949m. This large range means that the annual average temperature experienced at the highest and lowest sampling points could differ by as much as 5°C, which will allow us to look at temperature effects on soil biodiversity. As expected, the alpine soils were mainly fairly acidic with pH varying from 3.25-5.95, and averaging pH 4.62.
Soil biodiversity
DNA extracted from the soil samples was quality checked and sent to Berlin for sequencing. The resulting DNA sequences were used to identify the organisms present in each sample. We used three different DNA markers to capture as wide a range of soil biodiversity as possible. In total, we generated nearly 67 million DNA sequences, which represented 44,353 different types of organisms! It is worth remembering that from each sample we only extract DNA from a very small quantity of soil – around 250 mg. So, the total amount of soil which we analysed and in which we have found all this diversity is only 190 g (less than the volume of your coffee mug!).
What are all these organisms?
The myriad of lifeforms that share our planet are classified by taxonomists into seven ‘kingdoms’ - broad groupings of organisms each of which have descended from a common ancestor and which have similar body structures and characteristics. The term ‘taxon’ (plural taxa) is used to describe a group of organisms which are genetically distinct from any other. In most cases this would be equivalent to a single species. The chart below shows the number of taxa from each of the seven kingdoms that we found in our alpine soils.
Most of the soil biodiversity we found consisted of microscopic organisms and over half are bacteria and archaea. The protozoa include many bacterial predators with various forms of amoeba gliding over soil surfaces and consuming the bacteria they encounter. Fungi were easily the most diverse group after the bacteria and included those which form symbioses with plant roots as well as a range of decomposers and pathogens. Chromista are an extremely diverse group of organisms, with many known only from DNA studies such as this one. The ecological functions of most of the Chromista we found are completely unknown. The ones we do know about range from tiny parasites of other soil organisms to larger photosynthetic brown and golden algae.
There was also an amazing diversity of slightly larger life forms. For example, in the Kingdom animalia there were over 1500 different nematode worms, 327 amoebae, 205 mites, 87 water bears (tardigrades), and 56 flatworms. The final group of organisms detected are those in the plant kingdom. Not surprisingly these included many of the typical plant and moss species of our alpine habitats, but also a larger portion of the organisms in this group comprised green algae present on soil surfaces and the surfaces of other plants.
Alpine Soil Biodiversity Maps
At the start of this project we set out to create the first ever maps of alpine soil biodiversity across Scotland and, using this incredible dataset we have now managed to do just that. The maps below show the total number of different types of organisms from each kingdom found on each Munro (all three samples per Munro are combined). Clicking the image will open a larger version and allow you to scroll through maps of different organism groups and soil properties.
You can also explore the details of the diversity of soil life which was found in each sample by using our interactive map. Alternatively, if you want to find out which summits and samples hosted the greatest diversity check out our interactive results table. Clicking the column headings in the table will allow you to rank the samples to find out which had the highest and lowest diversity for each kingdom of organisms.
