A presentation I gave providing a brief glimpse into the effects that trees have on our lives and surroundings in an urban setting.
Presentation starts at 3:30.
Recently, in urban settings, trees are being used more as green infrastructure providing ecosystem services rather than merely street furniture. This presentation illustrates some ways in which this applies.
This presentation uses examples from the U.S, the U.K. and from India, where I am based. It includes the positive and negative effects and ways to improve matters with existing trees as well as potential trees. It is based on experience and research from around the world.
This is relevant for architects, town planners, municipal corporations, engineers, landscapers and anybody interested in improving urban forests through arboriculture.
Insisting on good quality tree seedlings from nurseries can ensure that your trees will thrive for considerably longer than plants already riddled with defects. This is an important consideration for trees that will live for decades or potentially much longer.
Some things to consider when obtaining trees from a nursery:
Bigger seedlings are not always better. The smaller the tree, the more it is likely to be in establishment mode (growing roots to be able to obtain the necessary water and nutrients for later growth and maintenance). It will need water and mulching to help it along but once it gets established, it may overtake plants that were planted as larger seedlings.
Selecting seedlings with a main stem will reduce potential future issues such as weak branch unions and damage to branches from rubbing branches.
Select seedlings with most branch unions in “U” form. Genetic variations or/and improper pruning can cause some trees to produce weak unions. This has been a major issue at times when large quantities of such stock have been planted along roads or in public places as they lose healthy branches periodically and will eventually need to be removed. This can be very dangerous if they have become large trees.
Avoid seedlings with damaged or diseased branches and/or leaves. This could otherwise mean that your plants would not survive very long and/or they might infect other nearby plants.
Some seedlings are sold grafted. This means that a scion (top bit which determines the fruit and flower) is fused onto a root stock (bottom bit which determines the vigor, ultimate size and drought resistance of the plant). One such example is the chikoo (Manilkara zapota) scion which is grafted onto a Manilkara hexandra root stock which helps it survive in the arid conditions of Auroville. Another advantage of grafting is that the plant will bear fruit earlier than normal as the scion will have been taken from an already fruiting plant. When buying grafted plants, make sure the grafts have fused properly. If a branch grows from under the graft union, you will get flowers and fruit from the root stock on that branch (which is often not wanted).
Check the roots before planting. Many seedlings are kept in containers that are too small for them. This often leads to roots turning around the container and creating girdling roots. The impact of this can be seen years later when such trees topple over or die from, essentially, self-strangulation. Some turning roots can be pruned if they are caught early enough but not if removing them would severely affect the health and then possibly the structure of a tree if/when decay sets in. If small roots are found circling at the bottom of the pot or bag that your tree comes in, they can be teased out or pruned if too thick.
The following two pictures show a tree that has failed entirely due to girdling roots: The tree has a stem diameter of at least 60cms and a height of nearly 10 meters. You can clearly see that it is lacking lateral roots.
We transplanted this (other) tree after it had been in the ground for several years. It had two roots which would have later damaged it and were therefore pruned.
What the roots looked like initially:
How it was pruned:
What was pruned off:
This tree will require a bit more aftercare than if it had been left with the defective roots but the long term effects will far outweigh the initial stress.
In the same way, trees properly grown and prepared in the nursery will be much more beneficial in the long term.
A brief article to inform people of how to go about digging near trees and why it matters.
Digging occurs for many reasons but the most important (for the tree) usually occurs when a trench is being dug for foundations or utility, such as for cables or pipes (there are many ways tree roots can be damaged but I am concentrating on digging damage).
Tree roots, usually, do not go below a meter in depth in the ground as there is not enough oxygen below to sustain them (through respiration). This is why it is usually feasible to dig under tree roots (Figure 8.16) instead of through them to install cables and pipes. For trees with tap roots, one can dig under the roots but to the side of the stem rather than directly under it.
Construction work near trees should be properly evaluated as most root damage to trees often occurs during this time but the effects will only be seen several years later.
Here is an example of poor planning and devastating results:
A new construction was planned to go around this tree (image) as it was a central focal point. The tree was not considered sufficiently. The result was that many roots were destroyed during excavation and a main branch was to be removed. I was called in by the owners who could clearly see that the tree had become a hazard as the above ground parts stretched for over 15 meters each direction and the below ground parts were all cut off at 1.5 meters in each direction. The only outcome was removal of the tree as the stability and health of the tree was severely compromised.
Construction work near trees should be properly evaluated as most root damage to trees often occurs during this time but the effects will only be seen several years later. The UK minimum root protection area is 12 times the diameter of a tree measured at 1.5 meters from ground level (a 12 meter radius for a 1 meter diameter tree). Before digging within this area root presence or absence should be verified. Foundations within this area are most often of the pile variety rather than the typical trench foundation.
Please think next time you want to dig near trees, especially if you want to build as close as you can to that special tree, because that may just shorten its life time significantly and defeat your purpose.
If you want more info, clarifications or advice, you are welcome to contact me. island@auroville.org or 7598103616
If you have a tree in India that you think might benefit from being moved to a better location, please get in contact with myself or Tree Care, India (link above).
We would also be happy to discuss details with regards to anything tree related.
I hope this will inspire people to move some trees instead of just chopping them down.
When tree surveys will/might be beneficial:
1: When buying a property that includes trees which might affect the initial or long-term price due to maintenance or removal of said tree(s).
2: Tree safety surveys (anywhere where many pedestrians or motorists visit often): in public areas such as schools, on private land or on commercial areas such as car parks. This serves to prove that the landowner is fulfilling their duty of care (not being negligent) and as such reducing the risk of damage to persons and property.
3: Development surveys compliant with BS:5837, 2012 Trees in relation to design, Demolition and Construction. To be included in planning applications where trees are present. This will also include trees that may be damaged by vehicular traffic on the site and will also include trees in neighbouring properties whose roots and/or branches may be affected.
4: A Condition report, to give a idea of the state of the trees on a site. This would possibly also include a management plan: what tree work is required or if other inspections (possibly aerial) are required down the line. This would include timescales for the work required or re-inspections.
5: Management plan: More often for older trees, veterans and ancient. If retrenchment is required to keep an old tree with a lapsed pollard from failing structurally, it may be beneficial to reduce the tree in stages and perhaps help it in other ways such as removing some competition (other trees), ameliorating the soil (perhaps with an airspade) etc… to enable reducing the tree without killing it a few years down the line.
