TOPIC: Site Characterization
== 1 of 1 ==
Date: Sun, Jul 27 2008 9:00 pm
From: "Edward Frank"
The willy nilly measurement of single trees gives you one measure of
a site. Since a site is made up of trees of different ages within a
species, with perhaps different maximum height potentials, and
growing in area with differing amounts of competition, light,
moisture, and nutrients, then measuring a subset of those trees,
such as the tallest of each species, is one way to characterize a
site. This measure has both strengths and weaknesses. The average
canopy height for all of the trees would also provide a different
way to characterize a site. It could be likely be done using air
photos or side scanning radar, but only at a great cost. What will
this number tell you given the variables involved in a particular
site, and how do you define the boundaries of a site? Lee apparently
has a methodology to determine average canopy height through a
series of measurements either along a line or within a give plot.
There are many ways to characterize a site. The question becomes
what ways give you a meaningful number? I am not sure that average
canopy height would be an improvement over a Rucker Height Index in
terms of information. Yes it would tell you something, and if
practical it would be worth measuring, but is it an improvement? I
Some sites have a good species diversity. They may have old trees.
They may have an unusual species assortment. They may have a unique
understory structure. They have have some important or interesting
characteristic that is not dependant on height. My problem is that
if height is the value being measured, and you are concerned that
height is not the best way to characterize the nature of a site,
then would a different way to measure height improve the situation?
My idea was to develop an aesthetics index, that would include a
bunch of ecological characteristics, with height being only one
category. A rating would be given to each characteristic out of a
long list, then an aggregate score would be compiled out of the
highest rated subset of those characteristics, much like all the
trees are not included in the Rucker Index, only those that are the
tallest. The exact configuration of parameters used to characterize
a site would vary from site to site, just like the tree species used
to compute the Rucker Index varies from site to site. I have not had
a good chance to work on it.
I'm a little frustrated with characterizing sites by willy-nilly
measuring single trees. I'd be nice if you could devise a radar that
would return the crown and the ground so you could generate two
surfaces. One for the ground and one for the crown height. Then you
could calculate the average difference between the two for the
average height of the forest as a whole.
== 2 of 3 ==
Date: Mon, Jul 28 2008 6:56 am
The technique for measuring canopy height, texture, downed trees and
more is already out there. As you probably guessed, it is very
expensive. LIDAR is a technique that uses a laser deployed on a
flying a grid pattern. The laser functions much like our range
finders to determine distances based on the return time of the laser
beam's "bounce" off of a surface. LIDAR is used most
commonly to map
terrain, and tree heights, etc, are filtered out as noise. However,
serveral recent papers in "Forest Ecology and Management"
with using LIDAR to quantify coarse woody debris. LIDAR could
certainly be used to map canopy height as well. For North Carolina,
the data has already been collected. All that is needed is someone
with the GIS and computer skills to turn the noise into canopy
== 3 of 3 ==
Date: Mon, Jul 28 2008 10:00 am
From: DON BERTOLETTE
And for tree/forest biomass volumes too!