Shade impacts to existing trees?

MAY

MAY

Location
Ontario
Hi everyone,

I have a question from the perspective of an environmental consultant: I'm working on a project where our client wants to build a 6 storey building next to an established woodland (mainly mature Red Oak and Sugar Maple). We have to evaluate what the impacts of the new shade will be on these trees but I can't find useful literature where this has been studied. I know that certain plants are shade intolerant but how does this affect existing vegetation, especially when the new condition is not full shade but partial shade at certain times of the year? If anyone has any ideas of literature I can look at or even experience tending trees in these sorts of situations I'd appreciate any input.

Thanks!

MA from Ontario
 
ISA website has archive of Journal of Arboriculture that might have some info and also check out arborcheck.com. They market instrumentation that measures chlorophyll fluorescence in the leaves to determine stressparameters. They may have some information available. Course they will try to sell you their stuff too I suppose.
 
Both trees mentioned will usually find their way in both shade and full sun. They want sun but many grow from the forest floor up through the canopy to find it. The thing to figure out is how much of an impact the shock of the instant change will effect them. And if the 6 story building will have an impact on shade, I would watch more for construction compaction and runoff. That's just going with my gut...without seeing anything of course.
 
The likely effect will be on the leaves it puts out in reaction to the available light. More shade would suggest the tree will respond with more "shade leaves", larger, thinner and darker. Initially the increased shade would effect photosynthate production. In the mature leaf it will reduce it and the subsequent winter bud will produce a leaf next season that is more like a shade leave. If the shading begins during the leafing out period the leaf will be somewhere in between, thicker but not as thick and I would think, larger. This is conjecture based on the following publication, http://jxb.oxfordjournals.org/content/57/2/343.full.pdf. Go to page 350 and the description of an experiment in the section titled How do C3 sun leaves have greater Sc than shade leaves?.

Based on shadow studies and shade analysis you may be able to get a sense of how great an impact the building may have overall on available sunlight to the woodland. If you consider what the impact of sustained light reduction is typically you may draw some theories on whether there will be dieback in some of the trees or limbs that are cast into perpetual shade. Furthermore, it would be safe to say, as Treelogic is suggesting, that you'll see, over time a change in form to more of a "forest" tree structure. Phototropism at it's best!

If the trees are protected from other stresses typical of a construction site then they may maintain sufficient vitality to adapt.

You may want to contact U of T's urban forestry dept and see if they have any research into this subject. Hey, you might actually be onto a great subject for a research grant!
 
A shadow impact study was done by the architect, and based on the orientation of the building and the forest there won't be a lot of sustained heavy shade. I'll look more to see if I can find resources to analyze shadow studies and also do another search of the Journal of Arboriculture.

Happily, one of the requirements of the project is that no impacts will happen within the dripline of the existing trees (it will be fenced), so construction impacts should be minimal.

Thanks for the input!
 
Yeah MAY, if you only knew how many times we've put up tree fences and had them trespassed, and filled with construction materials, piles of bricks etc. Monitoring the site is just as important as installation of the protection itself.

Once did a job where construction workers would throw circular saw blades (like Chinese throwing stars) into the trunk of a specimen tree for fun.

All contractors have to be made aware of the importance of the sacred, "no entry" zone. As Guy states above, hiring an arborist to do this is a smart move.
 
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