Whilst looking at trees that persist with just strips of sapwood, I thought I’d share these photos of a hornbeam within the same country park as the oak tree mentioned in my previous post. This tree was different to all the others, as it quite literally is half a tree!
Some months ago I was exploring a large country park and came across an open field, in which there two oak trees and a mound that housed a couple of ash. One oak was particularly intriguing, for in its retrenchment it has remained in existence with only one strip of sapwood on one of its sides – the remainder of the structure is simply exposed heartwood, which is colonised by Laetiporus sulphureus at least in part.
The below images, which show the tree from all four sides, really do speak for themselves, though we can see that a small ‘crown’ has formed from the only functional sapwood that remains. This oak, assuming the sapwood connection is not drastically damaged, may remain living for many decades.
For more information on veteran and ancient trees, the Ancient Tree Forum has released three publications in PDF format. These are: (1) Ancient and other veteran trees: further guidance on management; (2) Veteran Trees: a guide to good management; and (3) Veteran Trees: a guide to risk and responsibility. The latter two can be found on Natural England’s website split into chapters, though here they are found as entire PDFs. The first book is new (as of 2013), and was written by David Lonsdale. I advise that you purchase a hard copy from the ATF, if you can.
First and foremost, I wish to extend a thank you to David Humphries for confirming that what I was looking at here was Pseudoinonotus dryadeus. Given the condition of the (significantly lacking) brackets, I had only anticipated them being P. dryadeus because of the algal greening atop their structure, though having not seen this fungus in abundance it was very much an ‘educated’ guess.
The below pictures taken of the desiccated brackets around the butt of an oak (which sits on a woodland edge next to a golf course) are very telling. Classic bottle butt associated with a white rot (in this case, it is a selective white rot) can be seen, and consulting the very brilliant Arborist’s Field Guide by Guy Watson and Ted Green, the buttressing present here is indeed indicative of P. dryadeus decay. The authors state: “many trees stand on ‘stilts’ of buttress roots where the fungus has decayed the central wood completely, giving the appearance of the Eiffel Tower.”
Of course, failure is a risk. If decay extends into the buttress zones, or the buttresses have been weakened via other means, then windthrow may be of a higher possibility. Given this oak is a woodland edge tree, and the target zone beneath is frequently used (particularly in summer), management of the hazard via means of pruning may very well be something to consider.
Fagus sylvatica, once felled (or following death), can quickly become riddled with decay pockets. It is suspected that fungal endophyte species latently present within the tree’s system, which cause no disease / decay symptoms during the host’s life, are responsible for the rapid manifestation of decay following death. The exact entry of these endophytes in Fagus sylvatica is not largely understood, though it is anticipated that leaf scars, bud scale scars, the thin periderm, and lenticels are the main means of entry.
Laboratory experiments in the past have given weighting to such an assertion, when freshly-cut and healthy branches of Fagus sylvatica were incubated under varying drying regimes. After a period of 14 days, active mycelium could already be observed on the branches, indicating that latent endophytic fungi present at the time of the healthy branches being cut were the species now developing mycelial networks, and it is thought that the reduction in water content and increase of oxygen availability lead to the development of the mycelium (basically initiating the switch from latent to active).
Past studies had not shown that Fomes fomentarius, a very common white rot of Fagus sylvatica, could persist within healthy Fagus sylvatica for a period of time before the host’s death (or detachment of a part of the tree), though the decay strategy adopted by Fomes fomentarius (in Fungal Strategies of Wood Decay in Trees, the authors here allege, though I cannot find a specific direct reference to this in the book asides from comments regarding colonisation of the xylem in living hosts) suggests that the species should be able to exist as an endophyte prior to the right conditions manifesting within the host. The reason for past studies not showing Fomes fomentarius as an endophyte may perhaps be because past studies looked only at branch wood, whereas Fomes fomentarius is known to principally colonise the main stem and larger limbs of its host.
In this study, therefore, samples were taken in February from the ‘lower’ canopy (diameter: 5-10cm), ‘upper’ canopy (diameter: 10-25cm), and main stem (diameter: 20-50cm), in order to test whether Fomes fomentarius does indeed exist within healthy wood. 360 main samples were taken from ten (outwardly) healthy Fagus sylvatica, all of which were 70-85 years old, once they had been felled, and then the samples were transported to a laboratory and processed within 24 hours into 2,160 smaller samples.
Once the 2,160 samples had been processed and incubated for the duration of the study (either 8, 16, or 24 weeks), mycelium observed to have grown from the samples were analysed, identified, and recorded. Of the 2,160 samples, 61 had mycelial growth of Fomes fomentarius. The table below shows the breakdown of how long it took for the mycelium to begin developing, and in what samples they were found (lower canopy, upper canopy, or stem).
What can be ascertained from these readings is that, whilst not a common endophyte (in these samples), Fomes fomentarius can indeed exist latently within a healthy Fagus sylvatica. Analysis of the locations of the samples also suggests that Fomes fomentarius will exist most frequently within the stem, much less frequently within the upper canopy, though not at all in the lower canopy. The data also indicates that Fomes fomentarius will not immediately begin its active mycelial phase following host death, but instead manifest after 16-24 weeks (or even longer, though this study ended after a 24 week period). A period of incubation is thus necessary, and active growth is likely initiated by a change in wood moisture content and the increase of oxygen (which may be the result of cracks associated with the drying wood).
The study did also address concerns regarding whether Fomes fomentarius presence was simply a result of contamination post-branch removal, and the authors suggest that because the samples were taken in February, before the sporulating season of the fungus (starting in March across Central Europe, where the study was done), contamination was unlikely. Additionally, because isolates were found growing within heartwood of the main stem and ‘upper’ canopy (where diameters of samples were over 10cm in diameter, and up to 50cm), it is unlikely that contamination would have caused this – if isolates were found in the xylem of the ‘lower’ canopy samples that were 5-10cm in diameter, contamination may have been possible. Furthermore, the location of the isolates correlates with the position of Fomes fomentarius sporophores, which are typically found on the main stem of the host. Lastly, all isolates of Fomes fomentarius were genetically different, which means contamination to such extents would have been very unlikely (particularly given the time of year).
Interestingly, the study also mentions that there has been evidence recorded by Danby, Boddy, & Lonsdale (but not published, it seems) of Fomes fomentarius being latently present within Betula pendula as well.
Source: Baum, S., Sieber, T., Schwarze, F. and Fink, S. (2003) Latent infections of Fomes fomentarius in the xylem of European beech (Fagus sylvatica). Mycological Progress. 2 (2). p141-148.
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Certainly a more uncommon site, I came across this during the summer of 2015. As you can see, there are two decent-sized Inonotus hispidus sporophores within the crown of a Sorbus intermedia. One to keep a tabs on, given the location of the sporophores (right beneath the trunk’s trifurcation).
Trees provide fantastic amenity value year-round, though there are those times of the year when their beauty just steps up a level. An avenue of blossoming Japanese cherries in Spring lights up an otherwise dull urban roadscape, and the rich crimson red flushing of Liquidambar styraciflua foliage during autumn is a joy to behold in an urban park.
So when I was taking a stroll through a local open space, which is home to many Populus nigra ‘Italica’, I was awestruck by their intense golden colours on one fine afternoon during autumn. I admit, working typically within urban areas, I don’t oft see a Lombardy poplar have room to adopt an unhindered growth form (unfortunately many have their tops taken out because of the perceived risk associated with a tall tree, and the fact they are physically dominant, and block light), though this sight really gave me a different perspective on the Lombardy.
In this blog I will be sharing facts, experiences, and news associated with the arboricultural industry, in a bid to improve not only my own knowledge of arboriculture but help others expand their knowledge too. Posts will include book reviews, article reviews, facts (many will be cross-posted from my ‘Arboricultural Fact of the Day‘ thread on ArbTalk), industry news, general musings about arboriculture, and – perhaps at times – other things not so closely associated with arboriculture. The tagging widget on the sidebar should enable for simple navigation of my posts.
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