Tree Girdling How Long To Die

G.M. Moore
Burnley Higher, University of Melbourne, 500 Yarra Boulevard, RICHMOND, 3121

Abstract

Girdling and ring-barking of copse occurs for many reasons – vehicle impact, grazing past animals, insect and fungal assault and human being vandalism. Ring-barking that removes only phloem and cambial tissue has a vastly dissimilar bear on on tree physiology than girdling which removes phloem, cambial and xylem tissue. Girdling has an well-nigh firsthand issue on transpiration and so plants wilt apace and tissues can die within days. Ring-barking however furnishings translocation and and then causes a tiresome starvation of the root system and tin take many months or fifty-fifty years earlier root tissues start to die from starvation and the tree wilts and dies.

Many trees survive partial ring-barking, just how much of the vascular tissue needs to exist intact for plants to survive and what effective treatments are bachelor, if any, to arborists for improving the chances of tree survival? As little as 10% of vascular tissue may exist all that is required for an otherwise healthy and vigorous young tree to survive and recover. Furthermore, while ring-barking and girdling may non impale a tree they may leave it vulnerable to attack from insect pests and fungal diseases.

Tree management techniques such every bit span, approach or patch grafting may be considered as remedial treatments for ring-barked or girdled trees. Soil injection of sugar solutions may too be of benefit. However, making sure that the tree is free from environmental stresses and pest and diseases are important to recovery and allowing time for the tree to produce callus and wound wood.

Introduction

It is unfortunate the terms girdling, band barking, band-barking, ringbarking (ring-barking with the hyphen seems to about twice as common in use as ringbarking) and even ringing are used as synonyms to refer to the removal of a band or strip of bark which contains the cork and cork cambium, phloem and unremarkably the cambium around the unabridged circumference of a tree (Salisbury and Ross, 1992; Raven et al, 2005). It is unfortunate that so many terms are used for the aforementioned imprecisely specified activeness, as the depth to which the band of tissue is cutting can markedly bear upon the impact on the tree's vascular system and the subsequent effect on the tree of the action.

In this paper, ring-barking will be divers as a circumferential cutting made effectually the trunk of a tree which removes a band of tissue to the depth of an including the cambium. Such a cut removes a ring which contains cork and cork cambium, phloem tissues and the cambium and and so has an immediate impact on the translocation of materials in the phloem tissues. Girdling will be defined as a circumferential cut made around the body of a tree which removes a ring of tissue to the depth of the active or functional xylem tissues. Such a cutting removes a ring which contains cork and cork cambium, phloem tissues, the cambium and the current season's agile or functional xylem tissue growth ring and so has an immediate impact on both the translocational and transpirational processes. The merely way of telling whether a tree has been ring-barked or girdled is to examine the tissues which have been severed.

Because the furnishings and consequences of band-barking and girdling on trees are then different and impact on the tree over such different time scales, it would probably exist wise if unlike terms were adopted for the different actions. Such a distinction would bring clarity of pregnant to the terms, assistance in diagnosis of injury to trees, avoid ambivalence, aid in defining remedial handling and benefit the legal system in matters related to litigation involving either activity.

Causes of Ring –barking and Yardirdling

At that place are many dissimilar causes of band-barking and girdling from both natural and man interventions (Table 1). Both ring-barking and girdling have a long history of being used every bit management tools in forestry and agriculture for clearing land and removing trees from paddocks (Stubbs, 1998). Information technology is cost effective for selectively thinning forests and plantations and for the control of invasive woody species (Kilroy and Windell, 1999). In more subtle means, orchardists and horticulturists take used ring-barking and girdling to manipulate establish growth class, soluble carbohydrate content and fruit yield and production, but they are careful not to completely band-bark the whole stem or selected branch (Hartmann et al, 1981; Goren et al, 2004).

In urban arboriculture, the most common causes of band-barking and girdling arise from accidents, poor landscape management practices and attempts to impale trees. Accidental occurrences include motor vehicle accidents and wire and other not-degradable materials tied around tree trunks. Poor landscape management practices such as girdling roots from poor propagation technique, mower and whippersnipper damage, poor staking and tree guards, and pavement and physical surrounding trunks in paved areas can all cause serious damage. Finally, there are attempts at killing trees in disputes between neighbours and acts of deliberate vandalism (Harris et al, 2004).

Not all ring-barking and girdling damage, however, is acquired by human activity equally animal grazing, fungal and insect attack and poor root growth habit tin can occur naturally. While these cases are not all that common, impairment by sulphur-crested cockatoos (Cacatua galerita) can be all-encompassing and cause significant structural harm to large copse. Horses have also been known to ring-bark large trees in their paddocks by grazing the bark in great strips, obviously to come across a nutrient deficiency. Insect and fungal damage to trunks and large limbs is not uncommon, but usually affects trees that are already stressed.

Thdue east physiology of Ring –barking and Girdling

Ring–barking affecting ph50oem tissues and t ransport:

The effects of ring-barking, as defined before, on the physiology of a tree are dramatically unlike from the furnishings of girdling. The removal of the bark and cambium only has an touch on translocation via the phloem tissues, but h2o and nutrient send continues as xylem tissues are undamaged (Weier et al, 1982; Salisbury and Ross 1992). The removal of phloem tissues affects ship of complex organic molecules such equally sugars, amino acids and hormones, as well every bit other simpler substances dissolved in the phloem sap (Holmes, 1984). Transport of these substances from roots to foliage and stem above the region ring-barked is halted but so too is transport from the leaf to the root arrangement, specially of photosynthates and hormones.

The direction of transport through phloem tissues and its impact on tree physiology can as well vary according to the seasons. During periods of active growth when photosynthetic activity is high, send is oft predominantly basipetal from leaf to roots. Yet, in deciduous species coming out of dormancy in early spring, transport may be predominantly acropetal every bit carbohydrate stored in the roots and trunks is mobilized to facilitate bud burst and leafage product. Translocation and phloem ship is symplastic move of substances through the interconnected cytoplasm of interconnected living cells (Salisbury and Ross, 1992).

The ratio of the amount of phloem tissue to xylem tissue may be as loftier as 1 to 4, but is more usually nigh ane to six and in many tree species is closer to 1 to 10 (Fahn, 1975). The velocity of the motion of solutes through the phloem over long distances tin can be quite rapid, varying from about 100 – g mm per 60 minutes (Fahn 1975, Salisbury and Ross 1992; Atwell et al, 1999) with sieve tube cells emptying between 3 to 10 times per 2nd (Fahn, 1975; Salisbury and Ross 1992; Atwell et al, 1999). Interruption to phloem transport by band- barking and girdling would lead to rapid depletion of carbohydrates.

Tabular array ane. Some natural and human causes of ring-barking and/or girdling

Homo caused Ring-barking/Girdling	Naturally acquired Band-barking/Girdling
Agricultural killing of trees to clear paddocks	Grazing past animals, particularly horses
Foresters killing selected trees to thin stands	Stripping of bark by birds, such as cockatoos
Orchardists killing branches and controlling vegetative growth	Tunneling insects under the bark grazing on bark and cambial tissues to backlog
Orchardists controlling fruit, yield, size and sugar content	Fungal diseases, such equally collar rot
Placement of wires and nylon ropes around tree trunks and branches	Circling or girdling roots which can occur naturally, too every bit from poor nursery propagation
Unintended impairment from use of poor staking	Body harm from rocks, such every bit in trees germinating in crevices
Unintended impairment from mowers and whippersnippers	Bark eating rodents
Unintended root girdling of the stem by roots due to poor propagation and/or planting techniques
Accidental harm from motor vehicle impact
Unintended harm from construction works
Deliberate vandalism to torso and branches
Unintended torso damage from pavements and hard surfaces

The well-nigh immediate effect of these changes in transport is that hormones synthesised in the roots no longer travel above the zone of ring-barking and those produced by the foliage no longer attain the roots below. Ofttimes it is the interaction of different hormones at advisable concentrations that affect the physiological responses and so root and shoot growth and development tin can be impacted. Over the longer term, notwithstanding, it is the failure of photosynthate to achieve the root organisation that has meaning consequences that tin can kill the tree.

For some fourth dimension afterward impairment, growth and both branch and torso incremental increases to a higher place the zone of ring- barking keep. Indeed leaf condition may meliorate and incremental growth rates increase as all of the sugar produced by the leafage remains in the region of the torso and canopy, as none is able to reach the root arrangement. So the trunk above the ring-barked zone increases in girth and there is often a noticeable swelling above the ring-barking cutting. Growth below the cut slows and somewhen ceases and then an obvious departure develops in the body diameters higher up and below the ring-barking zone (Effigy 1).

Immediately after band-barking, almost copse have sufficient sugar reserves in the root cells to maintain an active jail cell metabolism and root growth. However, every bit fourth dimension passes these reserves are gradually consumed, at which point root growth ceases and root cells brainstorm to starve from lack of saccharide (Salisbury& Ross, 1992; Taiz and Zeiger, 2002). Water and nutrient uptake is then affected and the tree starts to shed foliage, foliage becomes chlorotic and finally, and often quite of a sudden, the tree wilts and the plant above the zone of ring-barking dies, which may result in the expiry of the whole plant.

Figure 1. Swelling above the cut on a ring-barked stem (Taiz and Zeiger, 2002)

For a large tree with substantial carbohydrate reserves and a adept root system, this procedure may take identify over a period of between 2 to 5 years. Nevertheless, if in that location are additional environmental stresses such as drought, flooding or waterlogging the decline of the tree volition be accelerated.

Girdling affectidue northg xylem and phloem tissues anorthd transpo rt

When girdling occurs, both translocation through phloem and transpiration through the xylem tissues are affected. However, the effect on transpiration is immediate as water supply to the trunk and canopy to a higher place the zone of girdling is cut and so on a warm windy day, wilting can brainstorm about immediately (McLuckie and McKee, 1954; Kramer & Kozlowski, 1960; Taiz and Zeiger, 2002). For most of the canopy and trunk higher up the girdling cut, permanent wilting will be reached within 24-48 hours depending on the size of the tree and environmental conditions. This girdling is a very effective method of killing establish tissues above the cut and the effects are almost immediate.

In dissimilarity to transport through phloem tissue, send of h2o and nutrients can be both symplastic and apoplastic (Effigy two). The latter is the motility of water and dissolved substances through the not-living jail cell walls and intercellular spaces of the plant. It is often forgotten that movement through the cell walls and intercellular spaces on a large tree can be quite significant and it is this movement and the properties of h2o, that get a long way to explaining why tissues immediately above cuts made in the trunk may not dry out or die. This may also explain why trees with major cuts though their trunks remain hydrated, healthy and growing.

It should also exist noted that some species have anomalous secondary growth (Esau 1965). Such growth may event in some trees having alternating rings of cambia, xylem and phloem while others have lobes of xylem alternate with phloem. For some species from some dicotyledonous plant families, including Myrtaceae, phloem may occur within as well as outside the xylem (Fahn, 1974). This intraxylary phloem may go far hard to effectively band-bawl or girdle copse that exhibit this unusual structure and may explain why some juvenile trees which appear to be band-barked or girdled remain unaffected.

Figure two. Symplastic and apoplastic pathways of plant transport (Salisbury and Ross, 1992)

The importance of the ring –barking and girdling cutting and tree responses:

The physiological response of a tree is besides influenced by the depth, width and location of the cuts fabricated to impact the ring-barking and girdling (Figure 3). If the width of the cut fabricated is quite narrow and so the tree may be able to abound over the cut by producing callus, which tin can differentiate into woundwood within weeks to a few months (Neely, 1988; Goren et al, 2004). Trees are well-known to take just grown over wire and other narrow obstructions, and band-barking bands narrower than 100-150mm have been known to exist grown over by large mature trees with substantial girths and sugar reserves. Deliberate attempts to kill trees past ignorant or lazy vandals accept also been thwarted when the cut narrow band (as narrow as 20-25mm) was simply grown over within a few months and the tree remained healthy and vigorous.

Effigy three. The width and depth of the cut affects the tree's response to ring-barking

Band-barking and girdling are large wounds and the usual tree response is to produce callus from the cambium at the margins surrounding the harm. Callus product is greatest in vigorous trees merely is affected by tree size, species and season (Neely, 1988). Spring, particularly early in the growing season, is typified past very fast responses to wounding and very rapid callus product, which can encompass the damaged surface. Callus and woundwood that predominantly develops from xylem ray cells grow best when xylem tissue growth is most active (Harris et al, 2004).

If the tree has dormant buds, such as axillary or epicormic buds, beneath the cut made to ring-bark or girdle a tree, these may be stimulated to develop by the cessation of basipetal transport of auxins from the canopy. The auxins will be the primary hormone involved in the inhibition of these dormant buds. If these buds develop with sufficient speed and grow to be large enough, they may send photosynthate downwards to the root system which will go along to blot and supply h2o and nutrients to the awning. Similarly trees that have adventitious buds or roots may provide a organization for circumventing the damage from band-barking and girdling.

In these situations it is possible that the parts of the tree in a higher place and below the band-barking cut may survive for very long periods of fourth dimension and even many decades. Species that tin can produce adventitious roots, such every bit species propagated by layering, for example Ficus species or some river red gums, E camaldulensis, are capable of surviving for decades, and possibly centuries nether such circumstances. Still, the part above the cutting usually eventually becomes stressed from environmental factors, such a drought or waterlogging, or the affect of insect grazing.

Some other of import aspect of ring-barking and girdling is the extent to which it occurs. There may exist full or fractional ring-barking and girdling of the trunk or major branches and stems. The effects of total ring-barking and girdling are clear, but a question arises as to how much of the vascular tissue needs to be intact for a tree to survive and recover over the longer term. Unfortunately there is trivial published information on this thing (Priestley, 2004) merely it is known that there is variability in response for dissimilar species of trees, which is also influenced by season and environmental conditions (Neely, 1988).

Trees accept certainly survived ring-barking and girdling to 50% of their trunk vascular tissues (Homes, 1984) and young trees of Eucalyptus camaldulensis, Platanus orientalis and Acacia melanoxylon survived and recovered from 60, 75, xc and fifty-fifty 100% damage (Priestley 2004). Furthermore, foresters trying to impale weedy woody species, such as beech, poplar and some maple species by girdling have reported how hard it can be (Glass, 2011; Kilroy and Windell, 1999). For the white poplar, Populus alba, which has the capacity to prolifically sucker, it has been reported that new bark can develop over the cuts in a matter of weeks (Glass, 2011).

The writer'southward observations have been that equally trivial as x% vascular connection tin can be enough for trees to remain healthy, if the tree is growing in ideal situations and is kept free of pests and diseases (Moore, 2011). Deliberate attempts to kill the celebrated Separation Tree in the Royal Botanic Gardens Melbourne in 2010 past ring-barking or girdling reported that a band of bark between 400 and 900mm wide was removed from lxxx% of the circumference (Fagg, 2012; Moore, 2011). With twenty% vascular connexion, the tree remains in total foliage, good for you and both callus and woundwood have been produced expanding the vascular connection. The woundwood differentiates into xylem and phloem tissues and new vascular cambium is also developed (Harris et al, 2004).

Other effects of Ring–barking and Girdling

One of the reported consequences of ring-barking has been an increase in fruiting and flowering, which is oft attributed to the retentivity of and higher levels of carbohydrate in the canopy of the tree (Kramer and Kozlowski, 1960), also as a survival response at times of farthermost stress (Taiz and Zeiger, 2002). This response is the basis of the employ of horticultural girdling and ring-barking, which unremarkably leaves between 10-20% of the vascular connectedness intact (Goren et al, 2004). Yet, there are little, if any data published on plant longevity after ring-barking or girdling.

In research on the effects of ring-barking and girdling young trees of Eucalyptus camaldulensis andPlatanus orientalis trees were girdled and Acacia melanoxylon, trees were ring-barked for sixty, 75, 90 and 100% of their girth (Priestley, 2004) using the definitions of ring-barking and girdling presented earlier. While the depths of cutting were unlike, the results were not as there were no apparent differences between trees in their responses regardless of whether they had been ring-barked or girdled.

Interestingly, whole tree or above cut deaths only occurred in the 100% handling. All specimens survived even 90% ring-barking or girdling, probably because the experiment was conducted over a 13 week period which was not long enough for plants to die and because the trees were juvenile and vigorous, they simply grew over the cuts that were fabricated to the trunks. Callus tissue is produced by repeated divisions of the about recent derivatives from the cambium with the bulk of callus (parenchyma) cells originating from cells destined to form xylem rays (Neely, 1988). Young trees would comprise a lot of such tissue. Withal, a number of interesting other effects emerged (Priestley, 2004):

For orientalis, the more astringent the treatment the slower the bud burst in leap and the less dense the canopy that subsequently developed (a greater response as y'all become from 60-100%). Later in the season the numbers of fruits produced by the ninety and 100% treatments were significantly lower averaging half-dozen.25 and iv.00 per tree respectively compared to xiv.25 for untreated controls.
For orientalis, the more than astringent the handling the greater the number of branches that were shed from these young tree (again, a greater response every bit you go from lx-100%).
For E camaldulensis, the undamaged controls showed an average increase in height of nearly 62mm, while none of the girdled treatments average over 30mm and most were considerably less.
For E camaldulensis, the level of Psyllid infection at the cease of the experiment was between lx and 90% for ring-barked specimens compared with an infection rate of 12.five% in undamaged controls.
For A melanoxylon, there was an effect for infection with leaf bane but in the reverse dir The blight afflicted control plants but was much reduced for the nigh severely ring-barked treatments.

What these data reveal is that even incomplete band-barking or girdling tin bear upon the growth and development of injured trees every bit well equally their responses to pest and diseases.

Arboricultural treatments for Ring– barking and Girdling

A number of arboricultural treatments for band-barking and girdling accept been suggested, including:

When bark is removed from a tree accidently or past vandalism, the bark should exist replaced in position immediately as natural grafting and callus growth tin take place so that growing over occurs very qui This procedure can be described equally bark patch grafting. The primal to success is speed, every bit the bark that has been detached cannot exist allowed to dry out nor can the damaged edges of the bark remaining on the tree dry. The work of Chandler (2009) showed that keeping eucalypt woody tissues moist facilitated successful callus growth and grafting success in Eucalyptus leucoxylon. Care must also exist taken to replace the bark at the right orientation so that, for instance, the part facing upward remains in that orientation and that there is as much contact as possible between the replaced patches of bark and the bawl on the tree (McGarry, 2001). The bawl tin be held in identify past whatsoever biodegradable material, but whatsoever fastening will suffice given the size and seriousness of the wound. Success may besides be afflicted for some species by flavour, with better rates of patch grafts occurring in bound and autumn for eucalypts than in winter or mid-summer (McGarry, 2001).
Bridge grafting is a well-known horticultural technique that has a long history of apply in repairing damaged orchard trees (Hartmann and Kester, 1975; Harris et al., 2004) simply it has also been used to repair damaged ornamental trees of historic, heritage, cultural, mural and horticulture significance which warrant the expenditure. The technique uses bark tissue from the same specimen, a clone, or the same species, which is inserted into the remaining healthy bawl of a band- barked or girdled tree. The objective of span grafting, as the name suggests, is to provide channels of connexion of both xylem and phloem tissue that allow send basipetally and acropetally over again (Figure 4). Success relies on salubrious cambium producing callus at both ends of the grafted bark and the rate of success can be influences past species and seasonal factors. Bridge grafting requires skill and is quite expensive to undertake and and so information technology is normally only contemplated for outstanding and significant trees. On a large tree, a number of grafts, upwardly to 10 or more may be inserted, and the aesthetics of the outcome are sometimes questioned past arborists and the general public.

Figure 4. Bridge grafting of a ring-barked trunk (modified from Hartmann and Kester, 1975)

Approach grafting and inarching are other well-known horticultural techniques used in repairing damaged orchard and valuable ornamental trees (Hartmann and Kester, 1975; Harris et , 2004). They differ in that for inarching, the top of the new rootstock found does not extend above the indicate of the graft matrimony. Inarching is considered to be a form of 'repair grafting'. Both techniques involve growing young seedlings that are progeny of the damaged establish, clones or at to the lowest degree of the same species as the damaged establish around the base of the damaged tree. The young trees should be of a reasonable size (1-2m in pinnacle with a stalk bore of twenty-25mm if possible) and the trunk or ane of the larger branches is then inserted into the healthy cambium of the damaged tree above the upper cut of the ring-barked or girdled region. The objective of approach grafting is to provide h2o and nutrients to the function of the damage tree above the zone of ring-barking or girdling, but it does not provide for transport downwards to the original root system. Nevertheless, if successful and given plenty time the young tree root systems develop as the original system declines and in some cases natural root grafting betwixt tree and seedling may occur (Tarroux and DesRochers, 2011). This technique is relevant when water is likely to be a limiting factor in the survival of a damaged tree and there is a significant adventure of imminent wilting. Again, approach grafting requires skill and is quite expensive to undertake. On a large tree a number of grafts, upwards to six-8, or more grafts may exist inserted, and the aesthetics of the upshot are sometimes questioned every bit there are a number of smaller trees growing around the trunk of the specimen.
Another aspect of postal service-damage direction that an arborist tin can undertake is to minimize the risks from environmental stresses. For the about part this will involve making certain that h2o and nutrients are not limiting and that at that place is no risk of waterlogging to the already stressed root organization. Good subsurface irrigation and drainage and proper mulching effectually the drip line would be useful practices. Mail-impairment control of pests and diseases is too wise (Priestley, 2004). Even partial band-barking and girdling of trunks or larger branches exposes plants to significant stress which may exit them vulnerable to pest and disease attack. For case, the assault on Due east camauldensis past the psyllid, white lace lerp (Cardiaspina albitextura) was confined to trees that had been ring-barked or girdled and not to undamaged control copse that were largely unaffected (Priestley, 2004). Psyllids are attracted to high nutrient levels in foliage and population numbers increment rapidly in these conditions (Collett, 2001) which is consistent with ring-barking and girdling causing an increase in sugar and carbohydrate accumulation above the zone of damage (Kramer & Kozlowski, 1960). Information technology is possible that these conditions might also suit some fungal pathogens.
Injections of sucrose into the soil have been reported to significantly improve fine root growth of established copse with responses dependent on species and the sugar concentrations applied (Percival et al, 2004). Information technology is unclear whether the response is due to the straight uptake of the carbohydrate the roots or to enhanced mycorrhizal growth, which would also do good the tree. The timing of such applications is as well critical. It should not be too early after damage as the roots, nether normal circumstances, should have sufficient carbohydrate reserves, but could exist applied when carbohydrate resources are in danger of depletion. Measurement of saccharide concentration in root tissue could inform the timing of application. Intendance must also be undertaken to ensure that the injected sugar does non benefit not-target organisms.

Decision

Depending on the tree and the weather condition that it is growing under, ring-barking may non mean the death of a tree, but picayune tin can exist done if a tree is effectively girdled severing the active xylem tissue. Arboricultural treatments that respond rapidly (inside hours) to the removal of bawl and which provide ideal growing weather condition for the tree heighten the chances of recovery from ring-barking. Treatments may involve irrigation, mulching, prevention of compaction and waterlogging and effective pest and disease command.

Depending on the species, environmental weather and the time of year, re-affixing displaced bark (bawl or patch grafting) can be successful if information technology is done within hours of removal and the tissues, both intact and displaced, have not dried out. If successful, callus product tin can be very rapid and growing over can occur within months. If the tissues dry or cannot be replaced other interventions such equally bridge or arroyo grafting may exist contemplated, but they can impact the aesthetic value of the specimen.

It should also be understood that healthy vigorous copse that announced to have been fully ring-barked or girdled, on closer and detailed inspection may show to have just been partially girdled or band-barked. Such copse may survive with as little as x-xx% vascular connectedness or less if they are young and healthy. Under these circumstances, the "do naught to the tree" option may exist an appropriate response provided that good arboricultural management practices are implemented subsequent to the injury.

Acknowledgements

The work of Sarah Priestly for her Industry Project Report at the Burnley Campus, University of Melbourne, is best-selling. I likewise acknowledge the contribution of my students in the 2013 Graduate Certificate in Arboriculture, Urban Tree Growth and Function, peculiarly Sian Flower, whose questions and essays on a related topic assisted in the writing of this newspaper. Ms East Moore, linguist, is thanked for her reading of and helpful suggestions for improving the manuscript. I as well thank Dr Sue Hughes for her excellent and thought provoking reading of the manuscript which enhanced the work.

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