Published by the International Society of Arboriculture.
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.
By D.W. Burger, G.W. Forister, and P.A. Kiehl
Abstract. Ten tree species common to the California landscape were grown from liners with or without treeshelters in the landscape for 2 years. Periodic (~ every 2 months) height and caliper measurements were taken and, at the end of the 2 years, all trees were harvested for fresh and dry weight biomass determinations. Response to the treeshelter microenvironment was species dependent. Height was greater for sheltered versus unsheltered trees during the first 30 to 250 days for all species After 2 years, only Ginkgo biloba and Pinus canariensis trees grown in shelters were taller than their unsheltered counterparts. Stem caliper was often reduced for sheltered trees. Treeshelters may be useful for tree establishment in the landscape, but should be removed once the tree has grown out of it. Staking likely will be required after removal of the treeshelter.
By Gary W. Watson, Patrick Kelsey, and Klaus Woodtli
Abstract. Soils were replaced in various patterns within the root
zone of mature landscape trees as an alternative to surface mulching. Care was
taken to minimize the damage to the root systems, through careful positioning of
the excavations, or use of hydraulic excavation procedures. Tree roots grew
better in the new soil mixes than in the original site soil, exhibiting up to a
320% increase in fine root density and up to a 68% increase in rooting depth.
Declining annual growth rate trends were reversed by the treatment in Tilia
and Platanus. Soil replacement has potential as another useful tool for
treating declining trees.
By Pavel Svihra, David Burger, and Richard Harris
Abstract. Treeshelters (Tubex® polypropylene tubes, 4 inch diameter, 4 ft tall) inhibited development of redwood tree (Sequoia sempervirens) roots. Unprotected redwood trees without treeshelters gained more root fresh and dry weight. Trees grown in treeshelters produced roots with smaller diameter. These data suggest that the treeshelter environment might temporarily prevent redwood trees from attaining optimal root development and anchorage. Redwood seedlings are not suitable candidates for establishment in treeshelters.
By Lawrance M. Lesser
Abstract. An inventory of the most common street tree species in 21 southern California cities was created. The inventory included information on tree species and diameter at breast height. The inventory indicates differences in existing species as well as differences in planting trends between coastal and inland regions. Links between the data and the potential for determining the age of the urban forest are discussed.
by Richard E. Close, J. James Kielbaso, Phu V. Nguyen, and Robert E. Schutzki
Abstract. Physiologic measurements of the internal water relations of sugar maple in a natural forest and along an urban street in Michigan were performed as a complement to a companion site characterization study. Investigations were carried out to determine how street trees are affected by the urban habitat, and to confirm through correlation analysis that site-related water stress adversely influences tree growth and vitality. Significant water relations differences exist between the street site sugar maples and those in natural habitats. Predawn water potential, osmotic potential, and stomatal conductance were significantly lower in the street trees, and were significantly correlated with the low soil moisture levels and high atmospheric demands of the street site. Findings of this study, in conjunction with the site characterization data, can be of value in selecting appropriate remedial treatments for stressed urban trees, as well as to reiterate the need for further screening of drought-tolerant cultivars for urban sites.
By John K. Francis, Bernard R. Parresol, and Juana Marin de Patino
Abstract. For 75 trees each of 12 species growing along streets in San Juan, Puerto Rico and Mérida, Mexico, diameter at breast height and distance to sidewalk or curb was measured and damage (cracking or raising) was evaluated. Logistic analysis was used to construct a model to predict probability of damage to sidewalk or curb. Distance to the pavement, diameter of the tree, and species were all found to contribute significantly to the probability of damage. Predictive models are presented for each species and numerical trials are used to illustrate the relationship of the independent variables to probability of damage.