Environmental Engineering Reference
In-Depth Information
10,000 m
2
The average tree density (in trees per ha) on each site
¼
per
ha/(mean m
2
per tree)
Mean tree density over all species total density
ð
Þ ¼
trees
=
ha
What was the mean density of
each different tree species
?
Mean density for Species A
¼ð
no
:
of trees of Species A
Þ=ð
total no
:
of trees
Þ
total density
5. If the total tree density on the site was 800 trees/ha, then the density of white pine
trees would be 0.10
800/ha
¼
80/ha. Compute the density for each
tree species.
Are some species bigger than others?
6. Foresters are often concerned with how big each tree is and how much wood is
on each site as a measure of profitability. Ecologists care about this, because
bigger trees can potentially exert more influence on an ecosystem. Tree size is
often represented by basal area, which is the cross-sectional area of each tree
(usually at breast height).
Calculate the basal area for each tree by using BA
r
2
. Use the diameter at
breast height (DBH) data to determine the radius (r) of each tree. Once you have
computed the basal area of each tree, find the mean basal area per tree of each
species on the site.
7. Next, compute the total basal area per hectare of each tree species. This is:
¼
π
no
:
of trees per ha density
Mean basal area per tree in m
2
ð
Þ
For example, if the mean cross-sectional area of a white pine tree was
2,000 cm
2
you would first divide this by 10,000 to convert it to 0.2 m
2
. Then
multiply this by 80 trees/ha (the density of white pines that we calculated above)
to find the total basal area. In this case it is 16 m
2
/ha. A high basal area can be
achieved by either having a high basal area per tree or a high density of trees.
8. Finally, compute the relative basal area of each species by dividing that species'
basal area per tree by the total basal area per tree for the site.
Questions
Use the data in your tables to answer the following questions in complete sentences:
1. What tree species is present in the highest density and lowest density?
2. What tree species is present in the highest basal area and the lowest basal area?
