| Biogeochemical
Cycling:
Trees and Carbon
Allometric
Equation
Carbon
| Determining
the allometric equations to use for estimating the amount of
carbon sequestered in a forest has been getting a lot of interest
in the last decade as countries debate global warming and the
effects of deforestation. One way for us to proceed would
be to use the equations developed by other researchers on similar
forests. For instance, Martin, Kloeppel, et al1
calculated a set of average equations for deciduous trees in
the southern Appalachian mountains that relate the diameter
of the tree at a height of 1.4 meters to various parameters
like the dry mass of the stem, the dry mass of the stem, bark,
and branches, and the total biomass of the tree excluding roots.
If we were to use these equations, we would not have to develop
our own equations, which would require that we sacrifice a few
trees.
The recent construction of apartments on the campus of KSU
and the clearcutting of the 15 acres of forest, though, have
provided us the opportunity to verify these equations.
Before the trees were ground up into mulch, we were able to
sample 5 representative trees (3 pines and 2 sweet gums) from
this location. Measurements of the circumferences of
the stems of the trees were made at multiple heights, allowing
for the volume of the stems to be calculated. Wood samples
were taken for age analysis and density measurements.
The wood samples were dried, and the densities were measured.
Using the density and volume measurements, the total mass
of the stem of the trees was found.
|
Picture
of one of the reference plots before trees
were clear cut to make room for the construction. |
|
Tree
|
Diam.
at 1.4 m
|
Stem
Mass
|
Age
|
|
Pine
#1
|
15.5
cm
|
89 kg
|
35 yrs
|
|
Pine
#2
|
32 cm
|
544 kg
|
54 yrs
|
|
Pine
#3
|
31 cm
|
467 kg
|
51 yrs
|
|
Sweet
Gum #1
|
18.5
cm
|
102 kg
|
37 yrs
|
|
Sweet
Gum #2
|
12 cm
|
31 kg
|
26 yrs
|
Now
that we have the masses of the stems and the diameters of the trees
at 1.4 m, we can develop our own allometric equation relating these
two and see how it compares to that developed by Martin, et al1.
If we plot this data on a log-log plot, we get
This data shows a relationship
between the diameter of the tree at 1.4 meters and the stem mass
of
log10M = -1.43 + 2.76
log10D
where M is the dry mass of the tree
above ground in kilograms and D is the diameter of the tree in centimeter
at 1.3 meters above ground level. This compares very well
to the results of Martin, et al of
log10M = -1.44 + 2.69
log10D
for the same relationship, given
the error bars on the data.
The fact that our reference data
for stem mass and diameter so closely matches that of Martin, et
al provides some evidence that the trees in our forest are similar
to those in their forest. This makes sense since the area where
their data was collected was at a location that is only about 100
miles from our site. Since our data is so similar, we are justified
in using their equation that relates the diameter at 1.4 meters
with total biomass of the tree (excluding roots) in our estimate.
This equation is
log10M = -1.25 + 2.66
log10D
1 "Aboveground biomass
and nitrogen allocation of ten deciduous southern Appalachian tree
species", Martin, Kloeppel, Schaefer, Kimbler, and McNulty, Can
J. For. Res. 28: 1648-1659 (1998).
|
