Hidden Fungi - Who, Where and When?
Some current research at Aberdeen University and The Macaulay Institute, Aberdeen
Many of the basidiomycete fungal fruiting bodies (mushrooms) we see in pinewoods form intimate, mutualistic associations (ectomycorrhizas) with roots of the trees under which they grow. These fungi play an important ecological role by providing nutrients for their host trees, which they obtain by breaking down organic matter in the soil. In return, the fungi are provided with a supply of carbon, for their own growth, from the tree. As much as 20 % of the carbon a tree obtains through photosynthesis from the atmosphere can be transferred to its ectomycorrhizal fungi - clear evidence for their importance to the tree! Although not as easy to see as fruiting bodies, if you look for instance under decomposing logs or mats of moss, you will often see stunted ectomycorrhizal root-tips, which are usually highly branched and often obviously sheathed in woolly hyphae. Some of the more common ectomycorrhizal fungal genera in our woods include Amanita, Suillus, Cortinarius, Russula and Boletus, and 5,000 - 6,000 species of fungi are thought to be ectomycorrhizal worldwide. There are often surprisingly large numbers of ectomycorrhizal fungal species within even small areas of woodland.
The question, 'Why are there so many different species of ectomycorrhizal fungi?' has fascinated ecologists for a number of years. Many believe it is because each species has a slightly different strategy, or specialisation, to survive in an ecosystem. For example, some species specialise on pine and others on beech; some may specialise at obtaining nutrients from fresh leaf litter while others obtain their nutrients better from well decomposed litter; some may form ectomycorrhizas mainly with young trees, while others only associate with mature trees. Some fungi may invest large amounts of energy into the production of exploratory hyphae that cover large areas of the forest floor in search of fresh nutrient sources. Others may remain close to their host roots and find fewer new sources of nutrients, but minimise the risk of being cut off from their precious supply of plant derived carbon. Some species may also avoid competition with other fungi by growing at different times of the year or by growing at different depths in the soil profile. The list goes on...
So how do we go about measuring spatial and temporal patterns in the distribution of ectomycorrhizal fungi in our woods? With some practice (!) we can identify ectomycorrhizal fungal fruiting bodies and plot their occurrence throughout the year. However, these fruiting bodies are like apples on a tree, and like apples, their absence does not mean the tree no longer exists! Some fungi may only produce fruiting bodies every few years when the conditions are right - this does not mean the fungus is not present in between these fruiting events. Others, such as members of the Thelephoraceae or Corticeaceae, produce cryptic resupinate fruit bodies which are easily missed unless you are an expert and are looking for them! Likewise, only small sections of the below-ground fungal network may produce fruiting bodies at any one time. Fruiting bodies are obviously not reliable measures of fungal distribution. With detailed descriptions of ectomycorrhizal root-tips (and a lot of patience!) it is possible to identify the fungi that form different types of root-tip. However, here again there are problems because we don't know how much the fungus grows away from the ectomycorrhizal root into the surrounding soil or how the seasons (and hence growth of the host tree) alter the number of ectomycorrhizal root-tips in relation to the fungal hyphae in the soil.
I've been working on mycorrhizas at Aberdeen University for the past seven years, and have just started an exciting new project (with Prof. Ian Alexander at Aberdeen University and Dr Ian Anderson at The Macaulay Institute) to investigate patterns of ectomycorrhizal fungus distribution in pine-forest soil (Culbin Forest soil to be precise). In order to overcome the problems of measuring the actual distribution of fungi in the soil, we will use recently developed molecular techniques to identify and quantify fungi as hyphae in the soil. To do this, we will compare genetic signatures of fruiting bodies and ectomycorrhizal root-tips found in Culbin Forest with the fungal genes we extract from small quantities of the forest soil. This will allow us to look at the real distribution of fungi throughout the year and across a relatively wide area... so we really will be able to find out who occurs where and when!
Another interesting application of the methods we will develop during this project is the ability to find out how rare the rare fungi really are. Perhaps some of the fungi we consider to be rare because we don't find their fruiting bodies very often, are in fact widely distributed but hidden underground? We'll keep you posted! If you'd like any more information about what we're doing, you're welcome to contact me by email or at School of Biological Sciences, Cruickshank Building, University of Aberdeen, St. Machar Drive, Aberdeen, AB24 3UD.
Dave Genney
11/12/03, Aberdeen
Back to Scientific Research in the Caledonian Forest
Pages about fungi on this site
- Ecological Features of the Caledonian Forest: Fungi
- Ecological Features of the Caledonian Forest: Mycorrhizas
- Scientific Research: Hidden Fungi - Who, Where and When?
- Photo Gallery: Fantastic Fungi!
- Species Profile: Pinewood tooth fungi
- Alder tongue fungus found at Dundreggan (and near Plodda Lodge)
- Fungi and Aspens: Promoting Biodiversity - Aspen friends and foes
- Fungi occurring in the Pinewoods in Glen Affric
- Fungi occurring on Dundreggan
- Mythology and Folklore of Fly Agaric
Published: 30 June 2004
Last updated: 25 August 2010