www.urban-forestry.com 39
The U.S. Forest Service's Pacific
Southwest Research Station recently published a
technical manual and launched the most extensive
database available cataloging urban trees with
their projected growth tailored to specific geo-
graphic regions.
"Knowing a tree's maximum size can avoid future
conflicts between
roots and sidewalks
or branches and
power lines," said
Greg McPherson,
research forester for
the Forest Service
and lead author of the
technical report and
database.
The products are
a culmination of 14
years of work, analyz
-
ing more than 14,000
trees across the United
States. Whereas prior
growth models typically
featured only a few spe
-
cies specific to a given
city or region, the newly
released database fea-
tures 171 distinct species
across 16 U.S. climate
zones. The trees studied
also spanned a range of
ages with data collected
from a consistent set of
measurements.
"There are very few studies, if any, in the world
that can compare to this in terms of scope with
regard to the number of trees studied, the species
analyzed, the geographic range and ages, and so
forth," McPherson said.
Advances in statistical modeling also have given
the projected growth dimensions a level of accu
-
Database Captures Urban Tree Sizes,
Growth Rates Across United States
racy never before seen. Moving beyond just
calculating a tree's diameter or age to determine
expected growth, the research incorporates 365
sets of equations to project growth.
"Although tree growth is the result of complex pro
-
cesses, growth equations capture changes in tree
size with age in a sur-
prisingly simple and
accurate way," said
Natalie Van Doorn, a
research urban ecol
-
ogist with the Forest
Service and co-au-
thor on the study.
In addition to pre-
dicted tree growth,
the manual provides
s p e c i e s - s p e c i f i c
data on foliar bio
-
mass, or amount of
foliage, that is crit-
ical to projecting
uptake of air pollut-
ants.
Written in a way
to be accessible
to non-technical
users, the technical
report gives step-
by-step instruc
-
tions on how to
use the equations
to calculate tree dimensions, bio-
mass, carbon storage and other features of interest
to urban foresters.
"The research and publication were done with
the urban forester and city planner in mind," Van
Doorn said. "Urban trees benefit communities in
innumerable ways, and it's this information can
help communities make the most of these natural
resources."
