Many people nowadays are aware of how important soil is. Whilst it’s not always the most glamorous of topics, it’s getting increased publicity for its important role as a carbon sink.  

So, what is it exactly that makes soil? Soil is created as a result of the interactions between mineral and organic material, physical features of the landscape, climate and time. Lots of time.  A layer of soil that is 1 inch (2.5 centimeters) thick may take 500 to 1,000 years to form. So, it’s not something that forms quickly! But it is incredibly important and very much alive.  It’s often quoted that there are more living things in one teaspoon of soil than there are people on the planet.   

^{A Tree Nursery volunteer plants Downy Birch seed in a long narrow soil bed. Photo: Lynn Cassells}
   
The health of our soil is something we don’t take for granted at our Cairngorms Connect Tree Nursery. If we don’t have healthy soils, we won’t be able to grow healthy trees so these are some of the things that we do.  

1. Avoid compaction  
One indication of healthy soil is that it’s light and fluffy. This means there is lots of oxygen in there, vital for all life. Our field beds are kept quite narrow with paths in between. This means we never have to walk or put much weight on to the soil in our beds and that helps to avoid any unnecessary compaction. Even rain can compact bare soil so we’re always delighted to see plenty of worms in there that help to keep it nice and aerated.   

2. Avoid unnecessary disturbance  
In order to give our trees the best chance to establish, above and below ground, we do have to keep our beds as ‘weed free’ as possible. When soil is bare, nature instinctively wants to cover it so keeping on top of grasses and other plants such as creeping buttercup and clover can be important. But we’re always mindful to not weed for the sake of weeding.  

3. Biosecurity measures  
Soil can become infected with pathogens if it comes into contact with other infected soils. Therefore, one of our protocols is that anyone coming into the nursery must clean and disinfect their shoes. It’s little practices like these which can be so important.  

4. No artificial chemicals  
We don’t spray any chemicals or apply any fertilisers (other than home-made compost) to our field beds.  Everything is as nature provides.  
 

^{Lynn Cassells holds two sprouting Hazelnuts towards the camera, soil under her nails. Photo: Lizzie Brotherston}

We’re always reviewing what we do to try to keep our soils in as tip top condition as we can. We also need to know our soils before we plant because not all soil is the same … 

In Scotland, the leading research body on soil is the James Hutton Institute, which writes of Scotland having four main soil types; podzols, brown earth, peat and gleys. Podzols and peat are on the more acidic side; brown earths are more neutral; and gleys can be alkaline to acidic, often characterised by the fact that they are waterlogged.   

And why do we need to know our soils in the Tree Nursery?  
There are a few reasons. Firstly, different trees will grow better in different soil types. For example, Hazel prefers a more neutral soil whereas Dwarf Birch will grow on acidic soils. And secondly, when planting out, we need to know about areas or pockets of deep peat so we can avoid planting on these.   

All soils are made up of mineral materials (sand, silt and clay particles) and organic matter (decaying plants and animals). Soils described as mineral soils are mostly mineral materials with less than 15% organic matter. On the other hand, soils are described as peat if they have a top 50cm layer of organic matter. We refer to these as “deep peat”.  

We don’t plant on anything that has greater than a 30cm top layer of organic matter. This is following guidance by Scottish Forestry and is because research now shows that planting on deep peat can result in a net increase in greenhouse gas emissions. Planting can dry out important peatland sites which will damage the habitat leading to greater carbon emissions than the grown trees would sequester. A lose-lose situation all round. 

^{A Tree Nursery Volunteer leans over a soil bed, one hand supporting them and the other patting down the soil over a just-planted seed. Image: Lizzie Brotherston}
 
Not only is today World Soil Day, but it is also International Volunteer Day so it is the perfect occasion to acknowledge the tireless, soil-covered work of our Tree Nursery volunteers! 

“Volunteering in the Tree Nursery is literally about putting your hands in the soil, and there is just enormous pleasure in that. People say dirt is good for you, and it really is!”  – Davey, Cairngorms Connect Tree Nursery Volunteer 
 
If you are interested in becoming part of this inspiring community, you can sign up using the Cairngorms National Park website by clicking here. 
Note: Volunteer sign ups are closed for December and January but we look forward to welcoming you to the Tree Nursery in February! 
 
The work at the Cairngorms Connect Tree Nursery is currently being funded by the Scottish Government’s Nature Restoration Fund, managed by NatureScot, and a generous grant from the LIFE programme of the European Union. Cairngorms Connect is funded by the Endangered Landscapes and Seascapes Programme. 
 

^{Feature Image: close up photo of a soil bed at the Tree Nursery, recently planted with tiny seeds. Photo: Lynn Cassells}