Select a title from the list below to see an abstract of the article. For information about ordering reprints of complete articles, contact ISA at (217) 355-9411 or isa@isa-arbor.com.
A Study of CTLA Formula Values
Gary Watson
Abstract. Appraisal records dating from 1980 to 1995 were acquired
from 51 casualty loss appraisers (usually for privately owned trees) and
24 municipal inventories (primarily for street trees). The final database
consisted of 3,966 casualty loss appraisals and 129,880 inventory appraisals.
The data from this study were used to develop a reference table of tree
appraisal values grouped by size and species classes. The table does not
eliminate the need to use the formula, but it does provide an individual
an opportunity to compare his or her appraised values to values of similar
trees. Appraised values of inventory trees were significantly higher (P
< 0.001) than values of casualty loss trees. The difference is partially
explained by larger size and higher location rating of inventory trees.
The average condition of all the trees appraised was rated as fair.
Impact of
Pitch Canker on Ornamental Monterey Pines in Santa Cruz County, California,
U.S., 1987-2000
Donald Owen and David Adams
Abstract. Long-term observations of ornamental Monterey pine
(Pinus radiata) showed that pitch canker severity varies considerably from
one tree to the next and over time. Most Monterey pines proved susceptible
to the disease, but many sustained only light to moderate levels of infection
and some never developed any disease symptoms. We developed a rating system
that proved useful in assessing pitch canker’s impact. Although the majority
of trees sustained heavy levels of infection, mortality was not a foregone
conclusion for even the most heavily damaged trees. After an initial outbreak
of pitch canker activity, the incidence of new infections decreased and
eventually dropped to an undetectable level. Trees are now recovering in
the absence of new infections. Application of this information will contribute
to better predictions of disease impact. It should not be presumed that
pitch canker will necessarily result in a high rate of mortality among
Monterey pines.
Equations for Predicting Diameter,
Height, Crown Width, and Leaf Area of San Joaquin Valley Street Trees
Paula J. Peper, E. Gregory McPherson, and Sylvia M. Mori
Abstract. Although the modeling of energy-use reduction, air
pollution uptake, rainfall interception, and microclimate modification
associated with urban trees depends on data relating diameter at breast
height (dbh), crown height, crown diameter, and leaf area to tree age or
dbh, scant information is available for common municipal tree species.
In this study, tree height, crown width, crown height, dbh, and leaf area
were measured for 12 common street tree species in the San Joaquin Valley
city of Modesto, California, U.S. The randomly sampled trees were planted
from 2 to 89 years ago. Using age or dbh as explanatory variables, parameters
such as dbh, tree height, crown width, crown height, and leaf area responses
were modeled using two equations. There was strong correlation (adjusted
R2 > 0.70) for total height, crown diameter, and leaf area with dbh. Correlations
for dbh with age and crown height for several species were weaker. The
equations for predicting tree sizes and leaf area are presented and applied
to compare size and growth for all species 15 and 30 years after planting.
Tree height, crown diameter, and dbh growth rates tended to slow during
the second 15 years, but the leaf area growth rate increased for most species.
Comparisons of predicted sizes for three species common to Modesto and
Santa Monica trees suggest that pruning has a significant impact on tree
size and leaf area, potentially more than climate and soil characteristics.
Influences of Community Characteristics
on Municipal Tree Ordinances in Illinois, U.S.
Shawn D. Dickerson, John W. Groninger, and Jean C. Mangun
Abstract. While the overall objective of municipal tree ordinances is to provide safe and attractive community forests, the approach to addressing this issue varies profoundly among municipalities. This study explores the relationship between community characteristics and municipal tree ordinances using data from 151 Illinois communities. Results show significant correlations between ordinance provisions and community characteristics relating to wealth and education. Communities with higher mean income and level of education are more likely to have provisions biased toward the maintenance and protection of existing community trees, while communities where residents are less educated and poorer on average tend to have ordinances focused on community aesthetics and safety through resource improvement. Municipal governments, and the tree care professionals advising them, can use this information for guidance when revising or developing ordinances to match community preferences and objectives.
Terravent™: Soil Fracture Patterns
and Impact on Bulk Density
E. Thomas Smiley
Abstract. Soil compaction is reported to
be a limiting factor in many urban tree plantings. The Terravent™ was developed
to decompact and aerate soil through the soil injection of high-pressure
nitrogen gas. The purpose of this project was to determine the soil fracture
patterns created by the Terravent and to determine if soil bulk density
is reduced. Replicates of six fractures were made at three sites. Bulk
density and the degree of fracturing were measured. No significant differences
in soil bulk density were found between treated and nontreated areas. Fracture
patterns were generally horizontal to convex shaped with a mean width up
to 22.2 in. (56 cm), typically 9 in. (23 cm) below the soil surface. Other
means of alleviating soil compaction are thought to be more effective.
Occurrence, Associated Symptoms,
and Potential Insect Vectors of the Ash Yellows Phytoplasma in Iowa, U.S.
Christopher J. Feeley, Elwood R. Hart, Janette R. Thompson, and
Thomas C. Harrington
Abstract. The ash yellows (AshY) phytoplasma has been reported
widely across the United States as an organism associated with ash decline
in urban communities. Prior surveys conducted in Iowa communities indicated
that AshY was found in up to 20% of the urban green ash (Fraxinus pennsylvanica
Marsh.) when using the DAPI (4’ ,6-diamidino-2-pheylindole.2HCl) staining
method. A new survey of trees in nine Iowa communities used polymerase
chain reaction (PCR) to detect the AshY phytoplasma. PCR analyses of tree
tissue were positive for AshY in 4% of the 240 trees surveyed. Although
145 of the sampled trees had decline symptoms similar to those exhibited
by trees infected with the AshY phytoplasma, the phytoplasma was detected
in only 11 trees. Because Homoptera have been shown to vector phytoplasmas,
insect populations associated with ash trees in two Iowa communities were
also sampled to help determine whether the insects were carrying phytoplasmas.
A total of 471 insects, representing 34 species, were collected from green
ash trees; of these, 396 were assayed for the presence of phytoplasmas
using PCR. Three leafhopper species were found that were reported to vector
phytoplasma diseases, but phytoplasmas were not detected in any of the
insects assayed.