29 October 2006

The young and the old

Last weekend at Belt Woods, I walked thru a section of the reserve that was clear-cut several years ago. The forest has since been regenerating, but the appearance of the forest was so different than that of the old-growth section where the trees are believed to have never been cut that I decided to post pictures here.

The first picture shows the regenerating 2nd growth forest.

youngforest

Here, all of the trees are young, have narrow trunks and their stands are dense. On the ground there is very little deadwood; what is there consists mostly of small branches. Because the canopy formed by the young trees is not very extensive, plenty of sunlight reaches the ground.

Compare this with the below photo of a typical scene from the old-growth forest.

oldforest

The old-growth forest (and in general, any old enough 2nd growth forest) is characterized by huge trees (in addition to younger ones) that are more widely spaced as well as a large amount of rotting wood on the ground. Also when the canopy is fully developed, especially in the summer before the leaves start to fall off, very little sunlight gets thru to the ground.

One additional and important characteristic of old forests is the thick layer of litter or humus consisting of rotting leaves and wood and other plant parts mixed with animal remains that covers the ground. This litter layer provides habitats and food for many small animals and fungi. Young forests growing on heavily disturbed soil, such as an abandoned farm field, lack this litter layer and it may take many years before enough of it accumulates.

3 comments:

matt said...

Many conservative, anti- (or at least non-) environmentalist folks like to point out that there are more trees now than there were before the turn of the century.

What they fail to grasp is that it's not the number of trees that matters, it's the complex heirarchies that are developed in the old growth forests that is important for the long-term support of biodiversity. Not seeing the forest for the trees in more than one way.

budak said...

I get the feeling that some statistics seem to include tree plantations (e.g. acacia and rubber estates for paper/pulp and rubber in the tropics) in their count of green areas....

leaf litter is a very interesting microhabitat.... i learnt recently that aquatic leaf litter accumulations (mature litters that have piled up and deepened over the years) in forest streams actually harbour species (Cobitiid fishes, shrimp) peculiar to these microhabitats.

Anonymous said...

Both statements are true with respect to there being more trees, but of less quality. What we also should understand is that contrary to popular belief, this country was not one wide swath of old growth. Natural disturbance (fire, insects, floods, etc...) and man made disturbances (clearing for crops and fires to flush game by native americans) actually created much more stratification of forest ages. Without a doubt there were tens of thousands of acres of what we would consider old growth, but they are natural systems that do cycle on their own. Places like the Belt Woods will eventually succumb to natural disturbance themselves and start anew, as all things do.