Ring barking and Sour felling- Let transpiration dry your wood.

As part of the ongoing drive to reduce reliance on heating oil, we are looking at providing a locally sourced economical, reliable and dry supply of woodfuel, initially for consumption within the glen. It is the dry bit I want to talk about today, particularly in relation to the supply of wood chip for for fuelling

I have recently written a report for the Forestry Commission on Ring-barking as a drying method. This report was written to accompany a felling licence application to carry out a first thin in a stand of larch trees using ring-barking as the thinning method. Drying wood chips to a low moisture content (MC) sustainably is a big challenge and I believe that ring barking (removing a strip of bark from around the tree, followed (unfortunately)  by a chemical injection) is a potentially very effective, low input method of naturally drying timber. Parts of the report follow below. Intrigued? Please carry on reading,.. feeling a bit bored already- that was probably the interesting bit above.

In Scotland's occasionally damp climate....

In Scotland’s occasionally damp climate, drying wood to a low MC within a set time period can be a difficult process, hence most wood chip suppliers supplement natural drying with a forced heat process, such as a grain dryer, forced air blower or kiln before storing the chips in a dry shed with a good air flow. Such processes inevitably involve expensive infrastructure and high energy costs, both in haulage/ double handling and in powering the drying machinery. Carrying out such processes reduce the overall sustainability of the end product as more carbon is added to it.

They also require the processor to have a substantial amount of space for housing the infrastructure and the sheds

Our situation as a community group with no property available to us does not currently let us contemplate a forced drying process, even if we wanted to.

We have therefore directed significant research towards natural drying methods and have come to the conclusion that, of the three methods assessed (drying in stacks and piles, ring-barking and sour felling), ring-barking or girdling the trees could offer most benefits, both in terms of low impact, low cost thinning and also in terms of a reduced MC product being produced.

Ring-barking

For a community group such as ours, which may need to build up a sustainable, low cost, low impact supply of dry or drying firewood for primarily local use, thinning by ring-barking may well be the optimum method to employ.

Using chainsaw, axe or scorp  and chemical injection an individual or a small workforce could carry out an inexpensive very swift, selective thin, without it being apparent that they had done so until some inevitable browning appeared in the canopy.  The canopy meanwhile remains intact (in a similar way to that of a self thinning mixture) until the tree is removed from it a year or two later by which time competition for light will have led neighbouring trees to begin to close the gaps left by the trees demise. The use of a thinning method that does not leave a network of holes in the canopy could be assumed to be an advantage in unthinned plantations at potential risk of windthrow.

It would also appear from our research that an optimum drying point can be reached where a stump attached sawlog still retains a high MC while the top third of the tree has reached an MC of 30% or below. In essence the top most easily processed third of the tree is ready for burning while the potentially economic bottom half or two thirds is still saleable or capable of being milled.

Ring-barking is an unconventional practice in the UK and while there appear to be many benefits from it, there may be drawbacks as well. Little research material is available on ring-barking, however another natural drying method called Sour Felling shares many of its characteristics.   

Sour Felling.

Sour felling involves felling trees and leaving them intact (whole tree) on the forest floor or in stacks at roadside.  Significant research has been carried out on sour felling as a drying method, principally in the UK, the Nordic countries and Canada.

Sour felling research experiments have reached the following conclusions:

1.      Leaving limbs and foliage on felled trees significantly increases moisture loss through transpiration compared to removing the limbs.  

2.      This enhanced drying effect lasts for a limited period of time, typically between 6-18 months. Some Swedish studies report an optimum transpirational drying period of between 4 and 6 weeks.  

3.      During the drying period foliage (needles or leaves) will drop from the limbs. If whole tree chipping for woodfuel is being considered, the loss of this foliage increases the calorific content of the fuel and reduces the ash content. Leaving the foliage on the forest floor returns a proportionate amount of nutrients to the forest cycle.

4.      The effectiveness of sour felling as a drying method is dependent both on the seasonal timing of the felling and the density of the remaining canopy.

5.      Sour felled logs will be lighter to remove from the forest, but MC’s will be variable throughout the crop. The research carried out into sour felling proves that an enhanced drying effect will be experienced if foliage remains on the tree following its demise.

Ring Barking and Sour Felling in Glenlyon

The benefits of sour felling as concerns transpiration will not only also apply to ring-barked trees but could be expected to be somewhat enhanced given that conditions in the upper canopy are somewhat more exposed to the drying effects of the elements than on the more enclosed and humid forest floor. Conversely it is unlikely that the tree as a whole will benefit from the reduced weight of sour felled trees, as moisture (trapped by bark) will drain down the cambium layer.  This is in accordance with general folk wisdom concerning standing deadwood that the tops will be very dry but at chest height the log will contain high levels of moisture.

Sour felling

Sour felling, as a drying method in Glenlyon appears to have numerous disadvantages compared to ring-barking.

A negative visual appearance is very much a disadvantage of sour felling. Looking somewhat similar to partially tidied windblow, sour felling would be an unlikely choice for a roadside thin in an area known for its sylvan beauty.

A potential knock on expense

From the point of view of the estates who own these forests having their forest edges slowly turned into something that both looks like, and presents, similar access problems to windblow could well be an unattractive option, both from a visual perspective and also from a “What happens if GWI folds and the estate needs to tidy up” point of view.

Sour felled Pine thinning in Glenlyon. The edges were thinned less heavily than the middle but are still pretty impenetrable as concerns access. Sour felling was only appropriate as the site was remote.

An increased fire risk could be an unwanted result of sour felling. Felled and delimbed normally much more of this visible (very dry) branching would be damply decaying in the grasses and bracken, that by now would be present as an under storey but are currently being shaded out by the brash. Having such “tinder” line the glen road may not be wise in terms of fire prevention.

The expense of, and need for, multiple operations makes Sour felling an expensive and complicated way to obtain a low value product ; Much of the unthinned woodland in Glenlyon is Sitka spruce, planted at a 2 metre spacing. The crowns of these trees are often locked together or entwined with those of their neighbours which can result in great difficulty in actually getting the tree down during selective thinning operations. Put simply – you fell them and nothing happens, they do not fall down or even necessarily move in the canopy.  To economically bring down these trees for sour felling would involve both chainsaw work and a winch assisted takedown. To have such infrastructure in the forest and to then “half do the job” i.e. to then exit the wood, without brashing or extracting to roadside, only to return a year or so later to reintroduce the equipment and finish the job (brash- extract to roadside) has obvious disadvantages for a small roadside operation such as ours.

Inconsistency in the drying effect makes forward planning awkward. I have been involved in various sour felling operations in Glenlyon. Revisiting these and measuring moisture contents revealed inconstancies in drying rates both in and across species. The pine in the photos, felled around 2005 was still reading, on average a fairly high 35% along its length. Some nearby Sitka sour felled at the same time was down to around 20% and one wind snapped Sitka spruce, down less than 2 years was 11-13% along its top third and around 19% in the middle and lower end.

The majority of the sour felled trees assessed by the author for this report showed heavy signs of predation by deer, with extensive defoliation presumably having happened early in the drying stages quite possibly during the first winter that the tops were on the ground. Such predation will obviously reduce the transpiratory benefits of leaving the canopy on. Deer are present in much of the woodland in Glenlyon and appear capable of moving through sour felled areas with relative ease.

Natural Drying Methods, Conclusion;

Of  all the natural drying methods assessed it would appear that the transpiratory drying processes (sour –felling and ringbarking) were of most value in reducing moisture content without incurring particular expense. Of these two methods, ringbarking potentially requires least handling and labour input, making it probably the most economical method.

Although much of the information on ringbarking is based on conjecture and folklore, there is no reason for it to be inaccurate and although there is a small possibility of deadwood related hazard, this would be little different to that of a self thinning mixture, in which dead crowns are enveloped by their light hungry neighbours.

The conservation benefits of ringbarking as a thinning method could be very high. Not only would it increase the percentage of standing dead wood, but an interesting light mosaic would appear on the forest floor, mimicking a natural cycle where a tree dies, but the dead canopy persists, then over time the tree falls and what little area of the canopy persisted is open to light, before the canopy eventually closes again.

Sour Felling as a drying technique is not visually attractive and creates a hazardous walking surface.  Its benefits in dedicated forest production areas, rich in machinery and labour and low in visitor interest could be very high should the end market require a moisture reduced (probably sap stain free) product.

The main practical disadvantage with sour felling is the need for machine assisted double handling, particularly when the stems are bunched together to dry. The main overall disadvantage with Sour Felling as a drying method for use in Glenlyon along roadsides and other amenity areas would be its negative physical appearance.

Drying logs in stacks is space efficient, but gives inconclusive results depending on stack location and the amount of effort expended in building it. Drying split firewood in stacks is a very good way to further reduce moisture content, particularly if the stacks are covered.

Weather conditions can greatly influence natural drying methods. It seems likely that ringbarked trees, exposed to winds running through the forest and standing away from the potentially humid forest floor will gain most from the drying effects of the elements. The transpirational benefits of seasonal ringbarking which involve the tree “flushing” in the spring are likely to advance drying further, also winter is increasingly a drier period overall than summer which, if humid, will slow down transpiration.    

My conclusion is that ringbarking could offer a space efficient, low input and low cost, relatively sustainable method of naturally drying timber. For our community needs and situation it appears a potentially very useful tool for providing an economical source of low moisture content fuelwood.

Open Day

It has long been my belief that in Scotland we have as many types of rain as the Inuit do snow. I have been compiling a compendium of these rain types for some time. The type of rain that fell occasionally during the open day is called Niar Llams, and it can fall for a while without actually making anything wet, although quite substantial in appearance in lacks in water delivery- it is the wet look of rain types and that was fine with me for the open day. It meant that the consultants could meet people and discuss the specifics of their situation in depth in the simply beautiful interior of Glenlyon Kirk, which we had kindly been allowed to use for the open day.

I had the night before discovered just how many people who would perhaps have been attending were away on holiday with their children. A reminder of how out of touch with holiday timing you get when you are self employed and also of how the demographics of the glen have changed of late. That there are so many families with children bodes well for the future of the school and the glen as a whole- Shame they were all on holiday when the open day was on though. That said I genuinely believe that a good time was had by all who did attend and I was pleased that most of the people who came stayed for the whole day.

Lots of people stayed for quite a while, having delicious refreshments helped.

Woodfuel Experts chat away, Bernd and Steve in the middle talk (presumably) woodfuel with fellow experts from  St Andrews based Stoveco. The table top is made from locally grown larch 225 years old, milled with a chainsaw and an Alaskan Mill.

Part of the plan for the day was about networking. Communities across Scotland are working together to improve their lives and environment, and the work being done at Tombreck with the Big Shed and Loch Tay Food Chain is really valid and inspiring. The Big Shed, built with timber from Bolfracks Estate and milled on site at Tombreck is really taking shape and is going to be of real benefit to the area as a nexus for creativity, shared learning and capacity building. The open day as a whole was a great opportunity for people to meet and chat (network).

Dennis Anderson of Scottish Sawmilling Services who did the milling for The Big Shed dropped in at the open day which was very nice.

Georgia's baskets and the Rowan poles looked the part.The wood slab is from a 300 year old oak

One of the highlights of the day was the Iron Horse demonstration, from Artcom Tradebridge, suppliers of interesting forest machinery. The demo was a bit later than planned and as such made a nice end to the day.

Hooray - It's time for the Iron Horse Demo'.

Although a small machine it can pull logs with ease.

Incidentally I was recently introduced to this rather good palindrome, from a 20 year entrant to a writing competition called U@50,  needless to say it stunned the judges. I thought I was clever realising Glenelg was a palindrome, but this is something else altogether....http://www.youtube.com/watch?v=aRG4ySdi_aE&feature=related

The day before Tommorow (special deja vu blog)

So as the big day approaches, is everything ready? "Probably" is the only answer I can give. In the last blog  I welcomed back my old friend Rain, who is welcome to go now, any time he wants to... Taxi for Rain please.... or at least be elsewhere on Saturday. This uncertainty with the weather is part of what makes it hard to know how ready you are.

 Oh Mighty God of Rain- Will you be blessing us with your watery gifts tomorrow?
If the weather is nice and sunny (no offence Rain) I plan to have some of the event outside in front of the church and have the consultants inside, answering questions and generally consulting on multiple aspects of wood heating. Outside will be the Loch Tay Food Chain and Big Shed representatives and also the various products for sale including some amazing woven creels, baskets an platters from local weaver Georgia Crook who has a studio and work on sale at Tombreck. 

J

Just a few glimpses of Georgia's work reveal both her talent and the incredible beauty and texture of the natural materials she works with - no plastics here.  

As to the day being a success, if just one person visiting tomorrow fits a wood heating system as a result of the information they have learnt then the day will have been a success in my opinion. Once that person, (very happy at having such cheap and good heating) starts telling their neighbours, " I wish I'd done it years ago" and people can see that these systems actually work and are not difficult to use, then more people will fit them.As woodfuelled heating systems become increasingly common, so oil heating with its ever rising cost and pollution will seem, even more than now, a poor solution to the problem of heating.

R

Rowan poles from Coppice Experiment 2, available for sale on the big day. An ideal gift for the Rowan pole collectors we all know and love.
These systems are so common in areas just like the glen all over the Nordic Countries, Austria, Poland, Germany, Canada, U.S.A.... In Finland there are numerous examples of wood fuel supply chains, often community owned cooperatives in which people take control of their own local heat needs. Local timber heats local houses, haulage costs are very low, so the fuel is more economical to produce and thus cheaper for the end user. Employment in forestry is guaranteed into the future, which ensures good sustainable forestry practice and as these chains are often community owned, any profit goes back into the community, rather than into the pockets of distant oil barons whose increasingly desperate ransacking of the worlds stored carbon (or oil) is paid for by our need for heat.
I certainly know where I would like the profits from heating my house to go and it isn't to Shell, supplier of oil to Glenlyon and environmental vandals par excellence. If Ogoniland was in America, not Africa then one day we might have seen Shell getting hauled over the coals alongside BP. The behaviour of Shell in Ogoniland is truly shocking, and deliberately so which makes it much much worse.

  Ogoniland in Nigeria, undoubtedly a lot nicer before Shell came along.

S

Gas flaring is a major contributor to global warming, a waste of energy and a serious health hazard. 

Rain Old Friend- welcome back, where have you been?

There has been excitement for the weather forecasters lately, bad weather on the way. Good. This has apparently been the most dry (or perhaps the most hot?) year since 1918.
I know its probably not a particularly popular opinion for most people, but I'm really happy to see Mr Rain coming to visit for a few days. We've had just about all sun (hot type) for a long time now and I have been missing Mr Rain as has the land.  He generally hangs about round here quite a lot, I remember one February (99 I think it was), when Mr Rain came and stayed for a whole month.

 Rain- so much more than just a way of making Rainbows.
We were working is smallish Sitka at the time and got soaked every day- everything, everywhere was wet , all the time, but when you work outdoors in Scotland, its not uncommon to have "precipitation anticipation" or be expecting some rain in other words. You soon get to know it of course and I've sometimes thought that I could match the Innuit's 80 whatever words for snow* with easily as many types of rain. If you were then to describe the accompanying weather pattern you would be into the hundreds. For example in Autumn in Scotlands most East- West aligned glen, we often have this pattern of really hot sunshine followed immediately by hard wet rain, they come in bands, one after another and can last for seconds a few minutes or ages, a bit like when you are out in the Islands and can see Mr Rain's little helpers scurrying about on the horizon with their little black sacks full of water to dump on wherever takes their fancy.

These Autumnal bands are nuts to work in, Its cold when it rains and the waters pouring off you, Then Lugh the Sun God jumps in and suddenly you are Roasty McToasty and steam is pouring off you. It is for me, weather like that that always puts me off the idea off moving to a hot country, You know (perhaps you don't, maybe its just me?) how it is, you go somewhere abroad. Really hot, "nice" Mediterranean type weather, your'e on holiday, everything's lovely, food, people, culture etc. At some point you idly wonder about moving there, wouldn't it be nice, ooh yes wouldn't it. Then by week 2 reverse cabin fever starts a little chant in your head " The weathers a bit boring isn't it?" "A bit of rain would sort out all this dust" "Its too hot to....do anything", " The weathers a bit boring isn't it?" and the answer is yes their continental weather patterns are pretty boring compared to our maritime climate.

So after having only had about 6 weeks in which it has rained since February, and having had almost unbroken and let me say, very beautiful blue skies right through from the winter snow to now, I'm glad for a few wet days, and from a view point other than the anthropocentric, all the flora and fauna are needing it too. Its strange though because although it must have been especially harsh for the Salmon Parr this year, trying to get upstream with so little flow, the wildlife especially insects and amphibians is really abundant this year. Frogs and toads being the most obvious example of that following the first drops of rain.

I

 I think this is an "Andrewlloydus webberus", but my toad ID is not very good.

One of many amphibians I encountered while doing some moisture measurements the other day.

Almost invisible in this photo; Camouflage and too small a photo size combine to hide a frog. I'll give you a clue, its not on the moisture meter.

Prior to that Insects were coming in vibrant bursts, during one particularly pleasant and colourful week there were Dragon and Damsel flies emerging everywhere, very sparkly in that ongoing, vaguely relentless sunshine. A few weeks before that it had been hover flies, truly remarkable close up like so many insects, and somewhere imbetween had begun the relentless march of the Beetles, as some but not loads of butterflies flitter overhead. I have seen a few lizards and slowworms have also been about (mostly victims of cars or cats), with the reptiles it constantly seems like some (usually unusually hot) years you see quite a few, some years you see none. What has been lacking of late in their usual abundance is Bee's, I keep hoping they are just a bit late gathering their numbers after the late frosts (the Midgies certainly are - Hooray), but I remain kind of concened.

T

There were blue and red dragon/ damsel flies all over the place, far too busy to stop for a photo. This picture in no way does justice to their colour.

  

Nearby here is a bank of Comfrey, which is grown for many reasons, as it has many uses. One is that the bees adore it, last year there were so many bees of so many varieties on it that it was almost anthill like in its hypnotic effect, you would see a few bees at first, then ten, twenty, a hundred, more, till there just seemed to be bees everywhere. This year it is more like 5, 10, 14, 20, 21 or is that the same one again, there is just not the abundance that there should be. Hopefully it is still just a bit early in the season for them and everything else is a bit ahead.

T

There should be umpteen bees in here- lets hope there will be soon. 
I met a nice and very interesting chap here the other day, while he was fixing a dyke (damaged by a bull) that he had built some time ago. He told me that the latest research on bees suggests that it is microwaves that are decimating bee populations, such as those used and emitted from Mobile phones. This is very worrying when you think how many people have them now, not just here but across the world.

Norman Haddow, a master craftsman at work.
They don't work in the glen, but the signals do leak through here and there for patient teenagers on holiday who will wait half an hour by a particular rock for a text to come through (it probably said "I'm on the train").
There is also a phone mast (for military use only) and also if you want to receive a TV signal you will need a satellite signal - Microwaves again.   
Anyway I have become diverted, I was going to talk about the rain and the sun and how everything as always needs to be in balance. Too much of either is not good and while we used to pray to Lugh and countless other sun gods for a good harvest, I bet we rarely did it with the concentrated fervour and immediate need that native American plains Indians would have carried out a rain dance. The rain dance as I understand it (a much misused term now) started as drought set in and continued until it rained. Participants danced and chanted until they dropped from exhaustion, when they recovered they got up and carried on, a trance like state was seemingly entered which perhaps helped to deal with the ongoing effect of dehydration. If it did not rain, drought, followed by famine and eventual death was a certainty. In rainy countries, somethings always growing so there is always something to eat, (read any John Muir book for proof- nice plate of Lichen anyone, this moss is very juicy?).

My little place in the country- I have been building this summerhouse for years, nearly finished now.


 *Peter Hoeg's "Miss Smillas feelings for Snow" discusses and explains these Inuit words very well.