Trees are amazing, spectacular, ingenious, astounding and magnificent.
Trees sustain, recycle and contribute to our very existence.
Trees house us, clothe us and heal us.
Yet, many, in the lustful moment of attempting to immortalize an ephemeral passion of eros, carve insignificant initials into the bark of trees. Initials that on average linger long after the amour that inspired their carving has evaporated to nothing. Initials that will ultimately infect and condemn the chosen tree to a slow death.
The very existence of trees is dependent on a complex process of chemistry to communicate within themselves and between their neighbours. Their chemistry defends against pests and microorganisms. The very diversity of tree species is dependent on evolution over millenia.
In the Garden Route alone, nature lovers can check off 139 species of trees compared to a meager 9 species in the boreal forest in Canada.
This diversity has been driven by a complex mixture of temperature, disease, rainfall and nutrient availability.
In the higher latitudes, the annual freezing winters have played a sanitizing role for any microbial pathogens and pest populations reaching an epidemic population within a host species. This annual cleansing has allowed single species to dominate vast areas without threat of an epidemic wiping them out.
Disease has led to diversity in low latitude forests.
By contrast, at lower latitudes, the mild winters pose no impediment to pests or microbial pathogens with the result that an infestation or disease can develop into an epidemic with the potential to kill a dense stand of a species.
Natural selection has driven the evolution of speciation to increase the spatial arrangement of trees in an endeavor to reduce the risk of infection within a species.
Within this complex spatial arrangement, there is a complex communication and inoculation system to combat infection and pest invasion both intraspecifically and intraspecifically.
The sheer time scale of tree longevity requires that trees have a means of both preventing infection and combating infection.
Defense strategies of Trees.
In super long lived species like Podocarpus falcatus and P. latifolius (Outeniqua Yellowwood and Real Yellowwood respectively), an auto pruning bark is the first line of defense against infection.
By regularly shedding flakes of bark, the potential colony of epiphytic flora is repelled, thereby reducing the risk of rootlets and hyphae penetrating the bark and inadvertently allowing the introduction of pathogens.
In the case of microbial infection, the second line of defense against infection in trees is the synthesis of an antibiotic. If the tree has the antibiotic present in its immune system, it can dispense it directly. In the event that it lacks the antibiotics required, it produces a chemical which moves to the roots and is transferred to the fungal hyphae that are integrated with the roots.
Wood Wide Web of Defense.
There are two macro systems of fungal mycelium integrated with the roots, namely an interspecific network that connects trees of the same species and secondly an intraspecific network connecting different species to each other through out the forest.
Both networks transmit the chemical identifying the pathogen at a rate of approximately 4cm/second. Any tree connected to the network that has the required antibiotic, then passes it into the network, where it is conveyed to an infected tree, where hopefully it can recover.
In the case of pest invasions, the tree first responds with chemicals to repel the pests. Simultaneously, it produces pheromones. One type alerts neighbouring trees of the presence of the pests. The second type of pheromones attracts the predators of the pests to assist in combating the pests.
In addition, the tree will transmit chemicals to the fungal mycelium both as a wide reaching warning of the pests presence, which stimulate other trees to prepare to repel imminent attacks, and to request pest repellent, which is delivered via the mycelium.
All of these communication strategies and chemical defense strategies have evolved since the dawn of trees emergence onto floral landscape.
So, when a hormone engorged hominid, armed with a penknife sets out to carve its erotic emotions into the bark of a tree, one of two consequences occur.
If by chance the blade is sterile, the wound from the carving allows airborne spores and bacteria from the immediate area to penetrate the protective defensive bark of the tree and infect it internally.
Oleo capensis, the indigenous Ironwood, is a species that is particularly susceptible to infection by this means. Lacking auto pruning bark, any breach of its bark is a potential site of infection.
Ironwood sap is rich in carbohydrates and is an ideal source of nutrition for pathogenic fungus. Initially it starts growing on the weeping sap, and can be seen as a black stain down the trunk, before entering through the wound and infecting the entire tree. Such an infection can take over 7 years before killing the tree, weakening the structural strength and resulting in it falling over.
Should the penknife blade be infected, then the potential exists that an infectious microbe from another region is introduced into the tree, and again condemn the tree to a slow, but sure death.
Infected by Love.
On the Giant Kingfisher Trail in Wilderness, there are two Outeniqua Yellowwood trees standing approximately 2.5m apart. For the past 15 years I have watched them and speculated on which one would die first. This speculation started when the Northern tree lost a lot of leaves and the crown was colonised by ‘Old Mans Beard’ lichen.
Both trees are approximately 320 years old judging from their diameter and height, mere youngsters compared to the potential age of between 900 and 1000 years life expectancy for the species in the region.
The leaf loss was during a drought period and the colonization indicated a reduction in the trees vitality. Compared to its neighbor with a full crown or leaves, it was blatantly apparent that this tree would succumb first, even if it took 5 decades. A natural tragedy of a life expectancy cut drastically short from a potential 900.
Then in 2005, the southern tree, despite all its auto pruning bark, was colonized by a strangling fig in the crook of a branch, a Ficus tree that has the potential of killing off the Yellowwood in 40 to 50 years.
The odds were once again even as nature rolled the dice of fate.
Then, in 2014, along came two blade yielding hominids, one with a machete which slashed the southern tree and another amour infused individual who carved K loves A in the northern tree.
These two acts have all but condemned both trees to a slow, though early death. In December 2014, around the sites of cutting, a fungal infection erupted with fungal fruiting bodies, more commonly known as mushrooms.
The extent was small, a nominal radius of 60cm. In the December of 2015, when the fruiting bodies again erupted, the radius was 1.5m. In December of 2016, the drought had obviously contributed to the deterioration of the health of both trees, though the infection rate now differed. The southern tree had a radius of 3m of fungal fruiting bodies while the northern tree had a radius of 7m.
Time will tell if neighboring trees of the forest will be able to supply a remedy for this fungal infection, but the larger picture is more concerning.
For some social dynamic seems to be encouraging a proliferation of tree carving in the Garden Route. Most trails now display initials carved on tree trunks and token attempts at romance scratched onto rock surfaces. In the midst of of global threats from over population, global warming, rising sea levels and encroaching distribution ranges, the very environmental sanctuaries that grace the Southern Cape are under an additional threat from informed lovers.
As a desperate plea to young lovers on behalf of the forests of the Garden Route, please broadcast your love on social media where at least your ephemeral eros will outlive the post.
If you are looking for some guided nature walks through the forests and fynbos of the Garden Route visit www.gardenroutetrail.co.za