| Rucker-area
curve: Observations
resulting from East Fork of Baxter Creek, GRSM, NC |
Robert
Leverett |
| Dec
07, 2004 06:09 PST |
Will:
You have defined for us another way of
evaluating and comparing
sites using indexes related to increasing area. I was struck by
the
small area associated with a rectangular swath 0.75 miles x 100
yards
wide. It is a little over 27 acres. So the Baxter Creek site
earns
151.24 points in as little as 27 acres. This puts the
extraordinarily
high numbers of the Smokies into better perspective. One does
not have
to include tens of thousands of acres to get to the big numbers.
Of
course you and I have known that for a long time, but your
acreage
figure ties it down and draws our attention to the high density
and
diversity of the tall species.
It might be interesting to look at the
clustering of tall species by
plotting Rucker points against increasing acreage. The X-axis
would
display increasing acreage and the Y axis would display the
Rucker index
for the corresponding acreages. The minimum value on the X-axis
would be
that number against which 10 canopy species (or an alternate
number)
were tallied. This approach could provide us with a simple means
of
making site to site comparisons. The labor-intensive nature of
the
analysis would necessitate doing this for only a modest subset
of our
ENTS sites. What do you think?
Bob |
| Rucker-area
curve? |
tpdig-@ysu.edu |
| Dec
08, 2004 13:41 PST |
Bob,
Will et al.,
That's essentially the same concept as a species-area curve, but
applied to tree
height index. Obviously surveying an entire area will give you
all species
present, but there is typically some much smaller area that is
meaningfully
representative in terms of species richness or diversity.
Increasing the
sampling effort yields a steadily lower chance of finding new
species (the
asymptote of the curve is the total number of species present).
I think the same
would prove true for a Rucker Index. For example, the Rucker for
Zoar Valley NY
is currently a little over 136', which includes about 70 acres
of streamside
terraces. I believe the Rucker Index for the ~8-acre Skinny Dip
Terrace (likely
the tallest) may be around 131'. I'd be curious to calculate the
mean Rucker
Index for a set of small plots just big enough to encompass ten
canopy species
each (on Skinny Dip Terrace these plots might be as small as 1/2
acre).
Labor-intensive, of course, but would probably yield some
interesting results.
Tom |
|