The Use of Bearberry Plants as Potential Afforestation Sites
Most land plants must form mutualistic associations with fungi to grow and survive, this relationship is called a mycorrhiza. The term originates from the Greek words: fungus – mykes and root – rhiza. Fungus-root perfectly describes the partnership. The roots of a plant are colonised by a fungus, through which the fungus obtains some of the sugars produced by the plant during photosynthesis. In return, the plant obtains substances it cannot produce, including nitrogen and phosphorous. This ancient relationship offers a long list of additional benefits, including water access, increased plant health and the formation of a complex fungal network which connects multiple trees within a forest.
Different forms of mycorrhizal associations exist, which vary in the way the fungus interacts with the plant root. Usually, plants and fungi can only form one type of mycorrhiza. However, sometimes a fungus will form different types of mycorrhiza depending on the plant they are partnering with. Four important types of mycorrhiza influence upland afforestation in Scotland, namely:
- The ericoid mycorrhizas, formed in most plants in the Ericaceae family. This includes the heathers, blaeberry, cowberry, and crowberry.
- The ectomycorrhizas, formed in most of our forest trees – Scots pine, the birches, oaks, to name just a few.
- The arbuscular mycorrhizas, formed by grasses, herbs and some tree species. This type is the most common and most ancient. It will be the topic of a later blog post, so stay tuned…
- The arbutoid mycorrhizas, an unusual type formed in only two plant genera – the Arbutus and Arctostaphylos. The only Scottish example of this is found in bearberry plants (Arctostaphylos uva-ursi).
This list is not exhaustive, but there is only so much information one blog post can cover!
If we take a fungal view of ericaceous heathlands (heather hills), they are dominated by ericoid mycorrhizal fungi, which trees cannot form associations with. This means that planted tree seedlings will struggle to survive, as there is no suitable mycorrhizal network for them to utilise. Thankfully, the uplands present an in-situ solution. Bearberry grows on ericaceous heathlands and in the low alpine zone. Interestingly, fungi that would usually form ectomycorrhizal associations with trees, form arbutoid associations with bearberry (Hagerman et al., 2001). This enables bearberry to host a surprisingly high diversity of ectomycorrhizal fungi. It is also a “non-selective” host, associating with a wide range of fungal species (Krpata et al., 2007). In a Scottish study, 19% of the fungi found on bearberry roots had previously been considered as specific to Scots pine and a smaller, but still notable proportion were previously considered specific to silver birch (Hesling and Taylor, 2013). A high diversity of ectomycorrhizal fungi has also been recorded in association with bearberry in the Austrian Alps (Krpata et al., 2007).
So, what is the significance of these findings? They suggest that bearberry plants act as islands of suitable ground for tree seedling establishment (Hesling and Taylor, 2013; Krpata et al., 2007). Each bearberry plant is likely to be surrounded by a network of fungal species which trees can form associations with. This can be seen in action in the photo below, taken at 730m above sea level in the Cairngorms National Park. The Scots pine trees growing in this area were concentrated in the vicinity of bearberry plants. The fungus in the foreground, growing directly next to the bearberry, is Suillus luteus, a species which was previously thought to only grow on pine trees (Dr Andy Taylor). This demonstrates the non-selective nature of bearberry as a host plant for fungi, enabling it to harbour specialist fungi which pine, birch and other trees require.
This knowledge could be used to advise planting locations on upland woodland creation projects. Planting pine and birch close to bearberry plants could greatly increase the chance of successful establishment and survival. The importance of mycorrhizal associations has only recently been realised. There is still so much to learn from this incredible kingdom of life, which potentially harbours many solutions to the challenges encountered during woodland creation.
References
Dr Andy Taylor –Molecular Fungal Ecologist at The James Hutton Institute
Hagerman, S.M., Sakakibara, S.M. and Durall, D.M. (2001). The potential for woody understory plants to provide refuge for ectomycorrhizal inoculum at an interior Douglas-fir forest after clear-cut logging. Canadian Journal of Forest Research, 31(4), pp.711–721.
Hesling, E. and Taylor, A. (2013). Ectomycorrhizal fungi associated with Arctostaphylos uva-ursi in Scotland: exploring the biogeography of undiscovered fungal communities. Karstenia, 53(1-2), pp.39–47.
Krpata, D., Mühlmann, O., Kuhnert, R., Ladurner, H., Göbl, F. and Peintner, U. (2007). High diversity of ectomycorrhizal fungi associated with Arctostaphylos uva-ursi in subalpine and alpine zones: Potential inoculum for afforestation. Forest Ecology and Management, 250(3), pp.167–175.
