Appendix

Oak – White rot

White rots are capable of removing cellulose, hemicellulose and lignin but have different strategies in the way they do this. Selective delignification white rots prefer to decay lignin and hemicelluloses and move onto the cellulose at an advanced stage of the decay process. Simulataneous white rots,as the name suggests are capable of degrading lignin, cellulose and hemicellulose from the early stages of decay. This can be a concern if the tree decay is extensive or located in a mechanically critical area of the tree.

The impact of the differences in the type of white rots can make a difference to the prognosis, removal of the cellulose reduces the tensile strength of the wood and removal of the lignin reduces the compressive strength. (Hirons,2016, 324-326)

Oak – Lonsdale’s autonomous functional units

Lonsdale recognised trees as a series of functional units and argues the case that trees can be better understood if the physiological requirements of certain branches, together with their associated sectors of the root system should be recognised as semi- autonomous units (2013,188)

This is trees survival strategy, allowing certain parts of the tree to become dysfunctional through aging or damage that are affectively protected from the spread of this dysfunction by boundaries that provide a degree of separation between the conductive pathways of adjacent functional units. By walling off such zones of dysfunction, enough lateral connections remain to allow fluid to move through new pathways. (196,2013)

“Dead branches can fail when they become brittle or decayed but their presence is usually of no concern in relation to the overall mechanical integrity of the tree” (Lonsdale,77,2013)

“potential failure of a decaying part might merely contribute to the process of natural retrenchment, whereby the crown of a tree becomes smaller and more easily supported, both mechanically and physiologically” (Lonsdale,78,2013)

Fire damage Lime – What’s happening internally

Wounds to the tree surface tend to the most easily damaged by the colonisation of fungi and bacteria immediately after the bark is damaged and before the tree can respond. The drying of any damaged wood, done by letting air in, allows for the microbes to grow. Thus the prognosis comes down to a race between tree ability to reduce the oxygen content and depend upon how rapidly the microorganisms can colonise the injury. (Boddy,1992) When the bark is damaged or breeched many species defences start in the living cells within the inner bark to develop and produce substances that can hinder the development of some microorganism and insects (Some microorganisms can use these substances as food however) Typically a dicotyledonous tree will produce oils and latex. The production takes place in the parenchyma cells around the wound or ooze from special reservoirs. Even in species where reservoirs are not found, pathological or traumatic canals can be induced through wounding. (Hirons,318,2016)

After the initial response of chemical production, repair will follow with minor wounds being treated by the initiation of wound periderms that typically occur from the anaplasia parenchyma cells located within the cortex of the inner bark. The wound periderm, an active defence mechanism, has the role of restoring a continuous physical barrier between the sapwood outside, yet a wound periderm is unlikely or unable to replace all of the lost bark and is only in operation during the growing season.

Parenchyma cells can become modified by suberisation and lignification of their walls known as metacutisation to become cork cells, its effectiveness is dependent upon the number and distribution of parenchyma cells on the exposed services. This again will only create partial boundary and eventual closure of the damage will be dependent upon wound callus create around the edge of the wound by the vascular cambium, with new wood growing inwards from the margins of the wound. This can take many years to complete and may never occur. (Hirons,319-320,2016) The fire may have impacted the defence mechanisms that normally activate following wounding.

Horse Chestnut PAE – Remedies

AIRSPADING -Any form of root damage reduces the trees ability to uptake water and nutrients, which could lead to water stress witnessed by reduced shoot growth, dieback and tree death (Cited Pervival et al,2004) Vertical mulching has been the subject of many research projects and Pervival et al concluded “ a soil injection system should be considered to stimulate fine root development…which should improve was and nutrient absorption…and aid there recovery” (2004,100) Yet Pervival et al’s research in itself is not conclusive and does state that some samples did not return any significant improvements.

Research has shown that resistance to bacterial infection can be enhanced however. This is done through applications of chemical and biological agents such as potassium, phosphate salts and plant rhizobacteria (Becot et al 2000, Fobert & Despres 2005, Krokene et al 2008 cited Percival & Banks 2014) however due the reduced impact of therapeutic treatments to pathogen attack, research has focused on improving resistance to pest and disease before attack, rather than during, this is an area of research that still requires further investigation.

As possible reasoning for this may well be in the way trees respond to bacterial and fungal attack.