humans and animals are lost in these fires because of how fast they burn down. They are tinder
dry most of the time and the oils cause explosions. The fires are too hot even for Lodgepole
pines as the cones experience temperatures too extreme. You have to take many precautions to
travel in Australia. Here is a tree that was almost burned to the ground and you can see the new
growth within a year. This strategy is developing shoots from the stump that remains. There are
enough tissues that remain buried in the stump to give rise to new branches. This is called
coppice shoots. Species that do this are loved by horticulturalists and they cut many trees so that
new shrubs start. Species that do this can regenerate after a fire. If some branches remain there
can be resprouting similar to coppicing up the tree. Almost all trees produce many more buds
than they actually use to have new leaves and branches in case of hard times. This is referred to
epicormic regrowth. These are seen in pyrophytes very readily. If you make a cutting from the
Eucalyptus tree it is easy to do. Some plants do this much better than others i.e. Forsythesia with
the yellow flowers and are very good at adapting to fire. Aspen trees also do very well after fires
and at epicormic sprouting.
There are 3 mechanisms that plants display that drive the course of succession. One is the
mechanism of tolerance. We just saw examples of this i.e. Sequoya and fires. It won’t die so it
will persist in succession for a long period of time.
Tolerance of light or shade is used to describe plant species. In this dense forest from B.C. you
can see how shade tolerant the smaller species are. At the bottom you will only find shade
tolerant trees/plants will live. Here we have 1-2 microeinsteins of light. As succession
progresses and shade intensifies the species on the ground have to be tolerant. This is a major
mechanism in succession when it comes to who exists and who dies.
Here we see many ferns as they are very good at extracting light on the forest floor where most
of the taller plants disappear. This is a White Oak Tree (on overhead).
(Picture of Algonquin Park) This is a sun tolerant tree (shade intolerant species). Junipers love
the sunlight and usually don’t survive in the shade. There are some shade tolerant ones that are
planted here on U of T campus and the shade of green will change because the plants will burn in
the sun. Norman Huner studies the interaction of low temperature and high light intensity and
when you bring them together you have to be perfectly adapted.
This is the 2nd one. This means that you are helping along the success of the plants that are
growing underneath. Under here you can see the seedlings of Thimbleberries. You often have
wild raspberries under the Aspen trees. The Aspens do not compete with the raspberries they
actually help them along. The soil is completely different for both. The Aspen help the
raspberry directly by lifting water up to the upper levels in the soil for the raspberries. Martin
Caldwell studied a phenomenon called ‘The Hydraulic Lift’ which means the roots of the trees
go way down and layers of the soil and water access is transported and oozed out at interface of
soil and atmosphere. That is only one means by which facilitation might occur.
BGYC61H3F.December.1.2008 Lecture 12 2