Trees & Fungi – made for each other

Adapted from Trees & Fungi, Their Complex Relationship by Professor Lynne Boddy – Part 3

We have been looking at the relationship between trees and fungi, based on the book by Professor Lynne Boddy [Trees & Fungi, Their Complex Relationship]. In part 2, Lynne explained that a tree will contain many fungi, most of which are beneficial. In part 3, Lynne explores this beneficial relationship. 

Beneficial fungi are mainly mycorrhizas. Around 90% of all plants will form a beneficial relationship between their fine roots and fungi, forming mycorrhizae. Mycorrhizal fungi extend into soil, often linking to multiple trees. The fungi form the absorptive surface for the roots, which is beneficial to the tree. For every metre of tree roots, there maybe 30-8000 metres of fungal hyphae. 

The fungi can absorb nutrients, being able to access the resource beyond the area of the root. Some can also obtain nutrients from dead plants. 

Some fungi are species-specific, others can connect with several species. Many trees form mycorrhizaes with many different fungi. One group of mycorrhizae are ‘arbuscular’. They can absorb nitrate, phosphate and other nutrients. They can also dissolve rock phosphate, providing additional phosphorus and increasing its availability in the local environment. 

Mycorrhizal fungi can also provide some protection against pathogens such as Phytophtora, which can be carried in soil water, and toxic heavy metals. 

Some plants, including both mature and seedling orchids, are unable to photosynthesise. They need to form an association with mycorrhizae in order to access nutrients, water and sugars. Without this, newly germinating seeds may fail to become established. 

Mycorrhizal fungi are crucial to trees, and it is important to encourage the association. This includes allowing the fungi to colonise naturally and to grow with good vigour. Mycorrhizal spores can be purchased from garden centres and nurseries, and it can be tempting to purchase these and add them to the soil around trees, especially those newly planted. Whilst this can work on reclaimed land, and when planting street trees, it rarely works in woodland settings. 

Retaining a tree’s own leaf litter, maintaining good moisture levels and avoiding compaction are all beneficial. Mycorrhizae prefer a slightly acidic soil. Soil pollution can raise acidity in the soil, and should be avoided. 

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