Trunk reiteration in a Sequoiadendron giganteum

One of the local parks has an absolutely stunning Sequoiadendron giganteum, which I valued (with the Helliwell System) at just under £100,000 in pure amenity value (which I’d say is a conservative estimate – CAVAT would value it much higher, I would suspect). Half way up the main stem however, sits a tree forming within a tree (trunk reiteration). Such a reiteration is really quite awesome, and in their natural range in California such trunk-trunk crotches can support entire mini-ecosystems, and as there may be dozens of these crotches in a single large specimen then one tree can support, in itself, an array of ecosystems (at heights of over 50m above ground). Obviously, the one here isn’t going to do that, though it’s a nice example of trunk reiteration in its earlier stages.

You can see it from here, actually. But this image is really just to give a sense of scale and importance to the tree. It’s literally quite massive.
A zoom-in from the same point as in the first photo.
And here we can really observe the reiterating trunk (half way up on the left). I would love to see how this looks in 50 years time!
Trunk reiteration in a Sequoiadendron giganteum

Severing roots to put in a fence

Sometimes I just have to wonder why. How does anyone think it’s even remotely a good idea to sever large roots to install a new structure? Surely it’s not even a case of lacking common sense, as it’s got to be instinctual to stop and think “hmm, if I remove this part of this object, will the result be something other than beneficial?”. In this case, the answer would be a resounding yes, and for that reason I’m flabbergasted that the individual still went ahead and sliced off a load of tree roots. Now, we can observe a hazard, whereas before we couldn’t have observed one.

One word: lunacy. We, as professionals, can learn as much as there is to know about trees, but such work can be undone so readily by those who just genuinely don’t exercise thought. A sobering lesson, perhaps, that we need to extend our reach to those who may never think, nor even care, about trees.

…and now let out a massive sigh, and question the sanity of some.
Severing roots to put in a fence

Using an electronic nose to detect decay in tree roots

Following on from my initial post about using electronic noses to pick up decay within a tree (which I suggest you glance over before reading this), I thought I’d visit further literature on the subject but with more of a refined focus. In this instance, we’ll be looking solely at the ability for electronic noses (specifically the PEN3 electronic nose) to detect decay within the rooting environment of trees. As was elucidated to in my previous post, the PEN3 can pick-up decay from root systems in the field setting, though here we can observe how a slightly earlier study fared in terms of its efficacy upon root samples inoculated in the laboratory and stored beneath different types of soil.

Because not all fungi will colonise the root system of a tree, the fungal species chosen in this study were Armillaria mellea, Ganoderma lucidum, and Heterbasidion annosum (a shame that Meripilus giganteus was not included). These three species can be considered principal root-rotters. These fungi were, once cultivated and made into mycelial plugs, brought into contact with healthy root samples (1-3cm in diameter and 2-10cm in length) of adult trees of the species Aesculus hippocastanum, Cedrus deodara, Liquidambar styraciflua, Platanus x hispanica, and Quercus robur. Such roots, complete with fungal inoculum, were then buried beneath sourced urban soils (and also ‘professional’ nursery soils), in order to reflect what soils the PEN3 would need to ‘sense’ through if it were to be applied in the ‘field’, and a period of time was given for the mycelium to begin colonising the root samples and. After a year, the samples were ready for testing. Then, following a set of complex processes that only a three-page methodology could ever fully encapsulate, it was time to look at the results (which are equally as complex, so I’ll do my best to simplify them).

What the researchers found was that the ability for the PEN3 to detect decay in the roots of different tree species by different wood decay fungi, all whilst under different soil types, was quite good (and more notably for urban soils) – see the below graphs. The nose was able to differentiate between healthy and decayed samples of root tissues with a high degree of variance between the two, meaning that there was little to no scope for ‘confusion’ between healthy and decayed root samples. Similarly, it was able to significantly differentiate between the fungal agents causing the decay in certain instances, and particularly in the cases where the fungi-tree relationship would naturally occur in the ‘field’. For example, the nose could identify (but not significantly differentiate between the two) oak roots colonised by A. mellea and G. lucidum – both are natural pathogens of the species. Granted, this trend wasn’t conslusive, as the nose couldn’t differentiate between healthy and A. mellea-infected samples in horse chestnut. The second set of graphs outlines the data collected with regards to differentiating between the decay from different fungal species.

The ability of the PEN3 to discriminate between healthy (green) and infected (blue) tree roots for A. hippocastanum (a), C. deodara (b), L. styracuflua (c), and Q. robur (d).

Under the urban soils, the nose worked more effectively, and this is considered to be because soils also emit their own VOCs, and professional nutrient-rich soils will have a ‘stronger’ emission. However, these professional soils still didn’t stop the PEN3 from identifying whether a root was decayed or healthy.

How the PEN3 differentiated between decay from different fungi (A. mellea [blue], G. lucidum [red], H. annosum [grey], and healthy [green], on the tree species A. hippocastanum (a), C. deodara (b), L. styraciflua (c), P. x hispanica (d), and Q. robur (e).
Evidently, some work is required in ensuring the PEN3 becomes very able to differentiate between the decay from different fungi on different tree species (and under different soils), though even from the graphs above we can see how there is, by-and-large, some degree of differentiation between the readings (as shown by the clusters, which infrequently overlap, but are sometimes close together). The decay from different fungi in Cedrus deodara appears to be particularly well differentiated, whilst decay in Aesculus hippocastanum is less so. Of course, it’s mainly a calibration and sensory game, and if the PEN3 can be accentuated in sensory ability then there’s certainly scope for this to be a very effective field diagnostic test for decay of root systems, and all whilst not having to damage the tree in any manner. Compiled with the more recent results of the PEN3 being able to work in the ‘field’, it’s an interesting piece of technology to keep an eye on.

Source: Baietto, M., Pozzi, L., Wilson, A., & Bassi, D. (2013) Evaluation of a portable MOS electronic nose to detect root rots in shade tree species. Computers and Electronics in Agriculture. 96 (1). p117-125.

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Using an electronic nose to detect decay in tree roots

A walk in the forest – the health benefits

I don’t think that one can question the anecdotal benefits of walking through a woodland or forest. Away from civilization, it’s a time where one can really begin to relax, let the mind shut off from stressors, and let the eyes take in the wonderful sights. I know, from personal experience, that a woodland walk can bring about a state of calm and ‘inner peace’, and I often find myself exploring for hours on end only to realise I’ve been gone for half a day, am slightly lost, and need to walk home before it gets too dark.

Personal journeys aside, there is a growing amount of evidence to state how woodland and forest settings can be used to reduce anxiety, treat (as part of a wider range of things) stress, and maintain a general good state of well-being. In this post, I thought I’d look at a study from Japan that assessed how the practice of ‘Shinrin-yoku’ (‘experiencing the forest’) can impact upon the mental and physical state / well-being of individuals (for this study, this was 12 male university students of 21-23 years of age). The forest in question was an old-growth broadleaved deciduous forest, and the experiment was undertaken in the height of summer.

In order to quantify the benefits of Shinrin-yoku, the 12 men were separated into two groups of six. One group spent the first day in the forest and the other in a nearby city (to enable for comparisons to be drawn), and on the second day the two groups swapped locations. All 12 men stayed in the same hotel, which was located around one hour away from either site (by car). Before leaving for each location, they would have breakfast, and upon return they would have dinner. Once at each location, individuals had their day planned so that they would first spend some time in a rest room on the site, and then go on a leisurely but lone walk (a pre-planned route) within the study area. They would then return for lunch at the rest room on the site, before remaining in the rest room to look at the scenery (by themselves). During each day, all individuals had physiological data collected from them, including blood pressure and pulse rate, before and after each activity (at the hotel for breakfast, at the rest room prior to the walk, after the walk, before looking at the scenery, after looking at the scenery, and back at the hotel for dinner). The men were also asked to rate, on 13-point scales, whether they felt comfortable or uncomfortable, and calm or roused (agitated). They were also asked to rank how refreshed they felt. Again, these subjectivity tests were taken six times each day, for all individuals.

The results of this study are very interesting, as they show that the 12 men almost always preferred the forest experience in a subjective sense, and their physiological measurements backed this up. Benefits were particularly evident after the men had experienced the forest (after the walk and after looking at the scenery from the rest room), though even prior to going on the walk and observing the scenery there were marked benefits (as if the expectation automatically improved an individual’s perception of well-being, and their physiological condition). Below, we’ll look at specific data sets and what they show.

How calm or roused the men felt at each site and at each measurement time. * p<0.05; ** p<0.01

In terms of how calm the men were, one can clearly observe how the forest walk had a significant impact upon their state of mind, which was even more significantly impacted following a period where they individually took in the view from the rest room site. Alarmingly, the men actually felt slightly agitated after observing a city vista. However, we can observe how the impacts on the feeling of calm were largely immediate, as by the evening there was no significant difference between the two data sets. However, the fact that those who experienced the forest felt calmer in the evening than those who experienced the city is interesting, as it is the inverse of the morning’s results, and even prior to the walk’s results.

How comfortable the men felt at each site and at each measurement time. * p<0.05; ** p<0.01

With reference to how comfortable the test subjects felt, we can clearly see how the forest experience (even when not on site, but eating breakfast at the hotel before heading out to the forest) made the men feel significantly more comfortable. The forest walk and scenery were particularly significant in raising the level of comfort within the men, whilst the city walk and scenery actually made them feel very uncomfortable. Following each walk and each observance of scenery in both locations, all men were significantly impacted by the experience, and the benefits and adverse impacts of these experiences have already been mentioned and can be seen in the graph above.

How refreshed the men felt at each site and at each measurement time. * p<0.05; ** p<0.01

Looking at how refreshed the men felt throughout the day, we can again see how the forest experience trumped the city experience. Again, the refreshed state of each individual rose significantly after each experience, and individuals were significantly more refreshed after forest experiences (notably after observing the scenery). We can now see a trend, that observing a forest view from a point of rest is certainly very beneficial, and studies on how hospital recovery time is positively impacted by the view of trees from a window now start to make yet more sense (as mental well-being manifests in the physical form, via blood pressure levels, and on on).

The pulse rate of the men at each site and at each measurement time. * p<0.05; ** p<0.01

Moving onto physiological impacts of a forest experience, we can see how the pulse rate of the men was, on average, lower before and after each forest experience, and also in the evening following the day’s experience. Only prior to the forest visit was pulse rate higher, and perhaps this was down to a form of excitement and / or apprehension (I am only speculating). Interestingly, the pulse rate of the men was quite markedly lower prior to the walk when they were awaiting a walk in the forest, suggesting that even the prospect of walking in a forest is physically calming, though curiously this doesn’t align fully with the men’s subjective feeling of calm prior to a forest walk. Therefore, we can observe perhaps a slight disparity between perception and actual physiological responses from the individuals to the prospect of a forest walk (perhaps, because walking in a city is more of the norm, they were more nonchalant about such a walk?).


The blood pressure of the men at each site and at each measurement time. * p<0.05; ** p<0.01

As for blood pressure, we can once again see how it was lowered in both the top (systolic) and bottom (diastolic) readings. Yet again we can see how the forest walk and observance of forest scenery were beneficial for lowering blood pressure, though this was more significant with the sitting down and watching of the scenery. Perhaps this is to be expected, as walking, which is a physical activity, will raise blood pressure (even slightly). Importantly, this benefit progressed into the evening, where evidently the men were still more relaxed, albeit not significantly so.

So there we have it. Forests are good both physically and mentally! Please, however, bear in mind this is only a study of 12 men of the age 21-23, so it’s by no means a conclusive study, but it’s a useful indicator of how a larger study might turn out. Further to this, it was done in the height of summer in a broadleaved forest of significant age, so we must also accept the marked benefit may also be seasonal (and younger forests, perhaps also coniferous in nature, may elicit a different response). There may also be differing cultural responses, and therefore replications in other areas of the world would also be interesting to see. I’ll let you look over the graphs again so you can form more conclusions for yourselves, though I hope this has been of use for many who are reading this. For me, it certainly aligns with my own experiences from walking through broadleaved woodlands. And I write all this as I overlook miles of fields and woodlands from my bedroom window, which has also had a very calming impact upon me – that is without doubt.

What’s not to love…!

Source: Tsunetsugu, Y., Park, B., Ishii, H., Hirano, H., Kagawa, T., & Miyazaki, Y. (2007) Physiological effects of Shinrin-yoku (taking in the atmosphere of the forest) in an old-growth broadleaf forest in Yamagata Prefecture, Japan. Journal of Physiological Anthropology. 26 (2). p135-142.

A walk in the forest – the health benefits

More books and more reading

And so, the book shelves continue to bulge. These additions are a little different to the more standard tree books, as I’ve taken an interest in understanding more about the traditional and cultural values of trees as of late (plus wanting to learn more about redwoods, before visiting next year). Below is the list of books, and where you can purchase them from (assuming you’re interested).

Links below!

Top rowThe Spirit of Trees (Hageneder, F.); The Olive: Tree of Civilization (Train, J.)

Middle rowThe Redwood Forest (Noss, R.); Coast Redwood: A Natural and Cultural History (Evarts, J. & Popper, M.); From the Redwood Forest (Dunning, J.)

Bottom rowPlants of the Bible and the Quran (Musselman, L.); Tree Wisdom: The Definitive Guidebook (Paterson, J.); Celtic Tree Magic (Forest, D.)

More books and more reading

Trametes gibbosa on a fallen hornbeam (Carpinus betulus)

It’s seemingly the beech that tend to be host to the greatest perennial fungal abundance in Epping Forest, and so whilst looking for fungi on constituent beech trees I came across a fallen hornbeam. On one of the larger stems, I noticed a cluster of fungal brackets, which turned out to be what I strongly consider is ‘the stumpgrinder’ Trametes gibbosa (syn: Pseudotramates gibbosa). Nice to see from a general interest point of view, and also good to see from a mineralisation angle, as this fungus is a very good decomposer of deadwood (hence the name ‘stumpgrinder’). Essentially, this’ll do what a mechanical stumpgrinder does (I suppose like many Trametes species), though in a more ecologically-friendly way and less instantaneously.

Pseudotrametes gibbosa carpinus1
Evidently quite markedly decayed already, if you look closely to the left of the image you can spot the brackets.
Pseudotrametes gibbosa carpinus12
Here they are upon the stem.
Pseudotrametes gibbosa carpinus13
A little closer, so that we can appreciate their morphology and colouration.
Pseudotrametes gibbosa carpinus14
Closer still!
Pseudotrametes gibbosa carpinus15
And the underside reveals the elongated tubes.
Pseudotrametes gibbosa carpinus6
Taking a cross-section, we can also see the pure white inner flesh and the depth of the tube layer.
Trametes gibbosa on a fallen hornbeam (Carpinus betulus)