Heart Rot fungal community research

Oak trees are long-lived, the oldest being over 1000 years old, but that does not mean that they are immune to decay. On the contrary, decay of wood in the centres of trunks eventually causes hollowing leaving a relatively narrow outer band of functional sapwood to support the canopy physically and physiologically. This decay is called heart-rot, and in oak (Quercus robur and Q. petraea) about 50% have hollows by the time they are 200 – 300 years old, although many of these trees have no external signs of internal decay.  All are hollowing by 400 years.

Heart-rot is a natural process and provides habitat for fungi (including the rare oak polypore Buglossoporus quercinus), rare saproxylic invertebrates and some vertebrates, and releases nutrients for tree growth. There has been considerable interest in decay of trunks of standing trees for over 200 years, particularly because of loss of timber. Research on tree pathogens continues but study of heart-rot caused by saprotrophs largely petered out 50 years ago, until recent work on beech. However, despite this long interest almost nothing is known about the development of decay in the trunks of standing trees. 

The most common fungi reported on oak trunks, based on fruit bodies, are Ganoderma australe (=adspersum), Fistulina hepatica, Inonotus dryadeus, Laetiporus sulphureus, and Meripilus giganteus. However, a recent study employing cores taken from standing beech trees shows that fungal fruit body surveys poorly reflect the fungi and decay that is taking place internally. The fungi are likely to gain entry by a variety of routes, depending on fungal species, including branches with and without heart-wood, large broken branches or stubs, with exposed heart-wood, bases of twigs embedded in the trunk, and via roots, and from latent endophytes within functional sapwood, though which route each fungus employs is largely unknown. Currently, very little is known about composition of these communities, how the communities change over time, whether they are entirely saprotrophic or whether in some circumstances they are pathogenic, the location, rates and patterns of decomposition in relation to wood anatomy, nor how this impacts on the organisms dependent on this habitat.

The project aims to address the gaps in the research groups knowledge mentioned above. This is essential for understanding what threats fungi may pose to oak trees, how to ensure continuity of heart-rot habitat essential to many hundreds of saproxylic invertebrate species, and the threatened rare oak polypore. They aim to fill this knowledge gap by:

  • Determining the main fungi involved in oak heart-rot in in the UK.
  • Analysing their 3-dimensional community structure in tree trunks (supported by coring studies, but mainly carried out on recently felled trees).
  • Assessing the presence of fungi latently present in the functional sapwood of oak.
  • Molecular detection of the rare oak polypore.