🚀 go-pugleaf

*** Note followup:  let's move this off ubc.general where noone outside of
campus can join in. 

In article <248pfv$91g@iskut.ucs.ubc.ca> holland@geop.ubc.ca writes:
>
>This argument is true if you think of a forest as a unit consisting of a
>single species of tree.  Replanting is a good way of creating tree farms
>but not a good way of rebuilding a forest.  Biological diversity will only
>redevelop if there is a near-by forested area that can "colonize" the 
>open space.  I don't know what distances such recolonization is possible
>over, or what the relative sizes of the forested vs cleared areas have to
>be but I would imagine that the larger the ratio the better.
_____________
Many, if not most, tree species have small, light seed with winged
attachments that allow for fairly easy dispersion.  Pioneer or early seral
species are excellent at dispersing seed (Red alder, for example), however
these species may not be desired from a management perspective.

Biological diversity is a more complex question than an assessment of a
forest at a single seral state, such as "old-growth" or climax.  After
logging, most forests on the coast are innundated by a variety of
quick-growing shrub and herb species that are not represented in later
seral, or maturity, stages.  These species are well adapted to spreading
seed from disturbed area to disturbed area.  Early seral stages are
optimum for different types of wildlife, such as deer which take
advantage of the abundance of forage, for example.

In fact, abundant shrub growth can hamper the transition to a forested
state by shading seedlings out or competing for moisture.  Planting, as
well as vegetation control techniques such as fire or herbicide
application, speed up the process of establishing the tree cover.  Once
full tree cover is established, vegetation diversity usually declines as
shrub and herb layers are shaded out.  Accompanying this change is a
change in wildlife as well.

Further maturity in coastal forest may see another period of increased
diversity as early seral tree species are replaced by mature canopy
species which reproduce in the shade of the mature forest.  Tree death,
either by tree-by-tree disturbance or old age, can provide canopy openings
allowing for a greater shrub or herb layer in the immediate vicinity. 
Late-seral tree species do not need to spread there seed quickly, as the
conditions for their survival do not exist until after the early seral
species have become established.  In fact, early conditions may likely be
detrimental to their establishment.

The diversity represented by changes in time is referred to as temporal
diversity and represents different levels of local, or alpha, diversity.
Another concept of diversity is the diversity across the landscape.  How
many different ecosystem types occur in a given area is known as beta
diversity.

It seems that in recent arguments surrounding forestry issues preservation
has been the forefront issue.  Should "preservation"in an absolute sense be
achieved in any given area it would seem that temporal diversity would be
ignored.  In fact, forest management has had its part in reducing temporal
diversity in some areas by managing to reduce natural forest fires, insects
and disease, and increase it in others through harvesting.  In my opinion,
it would be better to look at what advantages and disadvantages are
presented in different levels of the different types of diversity and make
management decisions around those options, rather than make an absolute
decision surrounding some concept of "preservation."

>It is interesting that the logging companies seem to prefer cutting in
>old-growth areas rather than regions that they have replanted in the
>past.  This suggests that either old-growth wood is not as poor as they
>tell us that it is, or that the replanting efforts of the past were 
>very badly done.
_____________
Large scale forestry has not taken place in B.C. for a very long time,
thus there are not many second growth forests ready for harvest.  We are
beginning to do so as they come into maturity, an example of which are the
roadside logging areas along the highway immediately north of Campbell River.
Large scale planting did not occur until the '50s or so and even then it
was not done with great knowledge. In many cases the wrong species were
planted for the type of site planted on and the forest establishment rate
was slowed as a result.  Modern planting follows much more strict
ecological assessment of forest sites prior to harvest to determine the
ecologically appropriate species or species mix.



-- 
Robert Froese  VE7MOQ
taganov biogeocoenose approach                  "Clearcutting is not a Crime"
taganov@unixg.ubc.ca