sampling methods for old growth?   Joe Zorzin
  Apr 07, 2004 07:15 PDT 
Just curious about the following: let's say somebody tells about a new property which they claim has some old growth, otherwise unknown to you old growth fanatics. <G>

Say it's 1,000 acres and you want to get a quick overview- do you just wander around in there looking for whatever big trees catch your attention?

The reason I'm pondering this is that I'm always trying to find better ways to sample forests for traditional forestry work- that is to prepare a standard forestry plan. Standard forestry techniques are ancient. Once it was done by measuring every tree within a fixed radius, say 50'- and the sampling plots would be distributed in any of a number of ways to get whatever kind of statistical accuracy you seek. Now of course most such sampling is done with a prism, so larger trees are sampled at a higher rate. Foresters all take a least one course in this subject, if not 2-3. Out in the real world, often, we don't do it quite as well as we could - since doing it really well takes a great deal of time and most of the time extreme accuracy isn't needed for a routine forestry plan and we can only charge so much for this work.

In recent years I'm doing it better because I'm now using the Mass. GIS orthophotos, released on CDROM- and, I got tired of trying to use a compass while pacing distances, so I finally got a "hip chain" which uses string and a distance measuring wheel. Hip chains have been around for decades, but I always thought my pacing was pretty good- so why bother- and I didn't like leaving string in the woods- especially after seeing a bird that had strangled on some hip chain string left by a surveyor. By the way, the latest hip chains can measure up to 4 miles!

But, now with the orthophotos and hip chain, I've decided to do a better job of cruising- the hip chain is so much more accurate than pacing- and because of that, I can lay out the plots on the photos, and find them- and I know that I can find those points as accurately and quicker than with GPS. So, now I'm taking a lot more plots with better results.

Say that 1,000 acre forest has bits and pieces of old growth forest within it- you could wander around and try to find them, and use GPS to locate them, but that isn't a very systematic way. If you did a systematic search, you may not initially find all the best trees, but you'd get a good sense of the entire property- as to roughly how many especially good trees or areas of good trees are out there on that 1,000 acres.

So, are you old growth dudes using such methodical techniques?
Joe Zorzin
RE: sampling methods for old growth?   Robert Leverett
  Apr 07, 2004 08:04 PDT 


When I'm in "old-growth mode" I'm not focusing on tree size, but on
forest characteristics that indicate an age distribution that supports
an old growth determination. That means I have to be very sensitive to
how aging characteristics develop on a species by species basis. When in
old-growth mode, I'm also looking carefully at ground-level
characteristics, not only for the existence of particular species, but
for mature plant colonizations that take decades to centuries to
develop. It is true that in good growing conditions tree size is going
to be larger on the average than for younger sites, but sizs isn't what
tips the scale.

Sites that can cause trouble are those that have been selectively
logged in the past for particular species. There may be an abundance of
old trees of a few species, but if the site is missing the higher age
classes for other species, especially commercially valuable ones, one
must be circumspect. This is an especially appropros for highly
accessible sites as opposed to those in extremely challenging terrian.

In terms of the OG designation, we're mainly concerned most with
identifying places that exhibit a high degree of natural development
that has likely occurred over a couple of centuries or more. Such sites
will usually have the requiste physical characteristics that are
generally associated with old growth for the forest type. There are
between 10 and 15 general characteristics that are routinely considered.

   Maybe it is time for a detailed discussion of these characteristics
for the different forest types. The Tree Amigos are getting geared up
for another year of OG mapping on DCR land.