"mhagen" wrote in message
...
This is good content - not theoretical at all. In the PNW, this is how
we cruise. Yes, a forester had better know what his findings mean in
the "real world" of non-mensurationists, on the other hand, he had
better be able to explain his procedures professionally too. If photo
cruises can do that for you back east, fine. That's not done often here,
except for cursory overviews. Partly that's because of the way we sell
timber - we have a lot of cash sales rather than stumpage sales and
values had better be nailed down to a few percent.


Oh, you're talking about a cruise for a timber sale? I thought the
discussion was cruising for mgt. plans. Certainly for a timber sale- you
need very good information. Here, only timber beasts cruise for a timber
sale, before they rip off the owner. Any reputable forester will mark and
tally each and every tree- a 100% tally. However, not even doing a 100%
tally, here, will give anyone accuracy to a few percent- since the trees are
difficult to accurately measure. Most hardwoods have irregular shapes,
forking- defects of all kinds, etc. so it becomes as much art as science.
What really counts is consistancy. The wood buyers keep a good record of the
results they get from each forester- so if I'm consistantly over by 15% on
some species and 5% on another- they know it- and they bid accordingly-
which makes everyone happy. Consistancy is the key. I suppose since you work
with mostly conifers which are more likely to be straight and round and not
forked- if you're carefull you should get much better accuracy- but with any
sort of a cruise that's not 100% I doubt anyone can get within a few
percent.



Back to the original question: having to derive a sample area when
using a relaskop is not kosher, but its done all the time to estimate
the number of plots needed before a cruise. Then sampling intensity is
adjusted in the field, depending on the findings. An BAF of 40 in large
timber is approximately equivalent to a 0.2 acre fixed plot for
estimating purposes only. As to whether one would actually DO a fixed
area plot, the advantages of using variable plots are so great in this
region (see that caveat?) that fixed plots are used only for
regeneration or research.


--
Joe Zorzin
http://www.forestmeister.com