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.
Designing Urban Pavement Sub-Bases
to Support Trees
by Palle Kristoffersen
Abstract. In Denmark, poor growth conditions for urban trees
have been perceived as a problem since the 1980s. Restricted planting-pit
sizes are mainly responsible for this problem. In 1996, a survey found
that the average size of municipal planting pits had increased from 0.1
m3 (3.5 ft3) in the late 1960s, to 3.4 m3 (120 ft3) in 1996. To increase
the volume of the planting pit, several materials have been introduced
to mix with soil to allow root growth under pavements. Three methods are
available for installing these materials under pavements. During the last
5 years, more than 800 trees have been planted on more than 30 sites using
these materials and installation methods. Every method has advantages and
disadvantages. No serious difficulties due to load-bearing capacity or
frost heaves have been recorded.
Progeny Testing in Street Trees
Subjected to Roadside Soil Pollution
by Oddmund Fostad and Per Anker Pedersen
Abstract. To investigate the relationship of the characteristics
of offspring from selected individual urban trees to the fitness of the
mother trees, seeds were collected in 1991 and 1992 from Acer platanoides
(Norway maple), Aesculus hippocastanum (horsechestnut), and Betula
pendula (silver birch) along streets in Oslo center, Norway. Half-sib
families of A. platanoides, A. hippocastanum, and B. pendula,
numbering 12, 12, and 6, respectively, were grown in the roadside soil
or in peat for 2 years (1992 and 1993) with seeds collected the previous
year. Seedlings grown in the roadside soil were 64% shorter than those
grown in peat. Stunting in roadside soil was greatest in A. platanoides
and least in B. pendula. In A. platanoides, a significant
correlation between height of the seedlings and vigor of the mother trees
was found in 1993 but not in 1992. In A. hippocastanum, a correlation was
found in both years. Within A. hippocastanum, best vigor and growth
were found in seedlings originating from mother trees with excellent vigor,
suggesting a potential for selective tree improvement. B. pendula
produced the most homogeneous seedlings. Leaf drop occurred earlier in
seedlings grown in roadside soil than in peat.
Locating Trees Using a Geographic
Information System and the Global Positioning System
by E. Brian Kane and H. Dennis P. Ryan III
Abstract. This paper reviews the basics of GPS and GIS technology
and describes their application for locating trees in rural park and forest
settings. During a hazard tree survey in a Massachusetts state park, project
members investigated the feasibility of using GPS and GIS to create maps
that highlighted individual trees and other landmarks. The project intended
to show that GPS and GIS can accurately locate trees. This technology is
especially useful for arborists and urban foresters who need to map trees
in rural parks, along rural roads and trails, and on large estates and
institutional land, where other location methods are impractical. Depending
on a variety of circumstances, GPS and GIS can be used in combination with
aerial photographs or standard line and symbol maps to create appropriate
tree maps for a particular area. Although certain problems still hinder
the mapping process, new technology developments will expedite using GPS
and GIS to produce maps.
The Horsechestnut Leafmining
Moth (Cameraria ohridella): A New Pest in Central Europe
by Christian Tomiczek and Hannes Krehan
Abstract. The horsechestnut (Aesculus hippocastanum) is one of
the most popular shade trees in central Europe. Although it was introduced
only 400 years ago from southeast Europe, at least 20,000 horsechestnuts
grow in Vienna and its environs. The horsechestnut was a tree species with
few health problems (e.g., Guignardia aesculi Ascomycetes) until the leafminer
Cameraria ohridella was imported—first to Macedonia and later on to central
Europe. The origin, biology, damage, population dynamics, natural limitation
factors, economic impact, management options, and control of C. ohridella
are discussed.
Correlating Foliar Nitrogen Levels
with Growth in Two Landscape Species
by Ed Perry and Gary W. Hickman
Abstract. Trials were conducted to determine the effect of applied
soluble nitrogen fertilizer on leaf nitrogen concentrations and growth
in valley oak (Quercus lobata) and Chinese pistache (Pistacia chinensis)
trees. Leaf nitrogen concentrations in valley oak were not significantly
affected by the fertilizer at 3, 9, 16, and 28 months following treatment.
Leaf nitrogen concentrations in Chinese pistache were not significantly
affected by the fertilizer at 9 and 12 months following treatment. The
fertilizer treatments did not cause increases in trunk diameter growth
in either species over the period of the study. Additionally, no correlation
could be made between visual nitrogen deficiency symptoms and actual leaf
nitrogen concentrations.
Biological Control of Elm Leaf Beetle
by Graham S. Thurston
Abstract. The bacterial insecticide Bacillus thuringiensis tenebrionis
(Novodor-FC®) (Btt) protected elm foliage from feeding damage by elm
leaf beetle larvae, Xanthogaleruca luteola, when applied to urban elms
by mistblower or roto-mist. Whereas untreated control trees lost up to
40% of their total foliage due to elm leaf beetle feeding in a 3-week sample
period, Btt-treated trees suffered only 10% defoliation. The entomopathogenic
nematode Steinernema carpocapsae, when incorporated into tree bands containing
cellulose mulch, proved effective at killing high proportions of migrating
larvae. The use of the bacterium and nematode together in an integrated
program may effectively reduce elm leaf beetle populations, thus eliminating
the need for chemical insecticides.
The Role of Arborists in Providing
Wildlife Habitat and Landscape Linkages Throughout the Urban Forest
by Julian A. Dunster
Abstract. In recent years, great advances have been made in arboriculture,
but the main design professions, the general public, and some arborists
still lack understanding about the ecological functions of trees for other
organisms, and how these ecological functions and processes connect across
larger landscapes. Consequently, many opportunities for the retention or
creation of wildlife habitat in the urban forest are still being lost.
Some of these opportunities are discussed, along with examples from British
Columbia. A selection of references from related fields is included to
provide a basis for further reading and understanding about landscape ecology,
greenways, wildlife trees, and how arborists might integrate the principles
from these fields into their practice.