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.
Damian F. Bresnan, Wayne A. Geyer and G. Rink
Abstract. Green ash trees from 18 provenances were planted in a seed-source test in 1971 near Manhattan, Kansas, in the central part of the Great Plains Region. Most seed sources were from north of the planting site. After 20 years, growth measurements revealed that the tallest trees were from more southerly sources and/or those near the plantation site. Trees from moderate distances north (150 miles) of the planting site also showed adequate growth. Height and dbh age-age correlations were highly significant and increased when compared to age measurements of earlier intervals.
Peter Simpson and Rufin Van Bossuyt
Abstract. In 1995, Eastern Utilities was among 14 utilities in the United States and Canada participating in a study to collect and evaluate data about the phenomena of how trees cause outages. Results indicate that failure of trees accounted for 40% of the preventable treecaused outages in the Brockton territory of Eastern Utilities. Even though line clearance tree trimming continues to be the primary strategy, programmatic changes were made in Eastern Utilities Tree Management Program. A Danger Tree Project was initiated to identify and mitigate trees with structural weaknesses along the 3-phase portion of the electrical distribution circuits. Approximately 4% of the trees in the portion of the urban forest managed by Eastern Utilities will either be removed or storm-proof pruned. Reliability has improved by 20% to 30% along the circuits where hazardous trees have been removed or storm-proof pruning has been done. Proactive communication within the community and participation in community-based tree planting has accompanied this project.
Richard J. Hauer and Jeffrey O. Dawson
Abstract. Ectomycorrhiza formation, biomass production, and iron accumulation were determined for pin oak (Quercus palustris) seedlings grown for 2 years in acidic (5.5 pH) or alkaline (7.5 pH) media and inoculated with soil from 1 of 3 sites: 1) a native pin oak forest, 2) an urban site with chlorotic pin oak trees, or 3) an urban site with non-chlorotic pin oak trees. Ectomycorrhiza formation on pin oak roots was similar for soil inocula from all 3 sites, similar for both pH treatments, and lacking on non-ectomycorrhizal seedlings that had been inoculated with autoclaved soil. Seedling biomass was greater in the acidic medium than the alkaline medium. Inoculated seedlings in the alkaline treatment had greater biomass than uninfected control seedlings inoculated with autoclaved soil in the alkaline treatment. The mean iron concentration of seedlings grown in the acidic medium (54.3 ppm) was significantly greater than that of seedlings grown in the alkaline medium (48.7 ppm). Inoculated seedlings had similar mean leaf iron concentrations despite pH differences (49.3 ppm under acidic conditions and 52.7 ppm under alkaline conditions). Mean leaf iron concentration was lowest for the uninoculated seedlings in alkaline medium (44.8 ppm), suggesting that ectomycorrhizae contribute to iron accumulation in pin oak under alkaline soil conditions. Results indicate that ectomycorrhizae influence both growth and iron sequestering under iron-limiting conditions and that some urban soils harbor infective pin oak ectomycorrhizal fungi.
Scott R. Templeton and George Goldman
Abstract. Urban forests provide tree products and aesthetic, recreational, health, and environmental benefits. Yet the expenditures that people make to secure these benefits are difficult to estimate for lack of comprehensive published data. Based on various sources of data, we estimate that Californians spent at least $947 million to obtain these benefits and the state s urban forestry sector had sales of at least $1.115 billion in a 12-month period in the early 1990s. As a result of direct, indirect, and induced effects, urban forestry accounted for at least $3.384 billion in total sales. This level of sales became about $1.869 billion in annual income to individuals and supported about 57,200 jobs in this period within the state. Knowledge of this economic activity is important, in principle, to voters and public decisionmakers who allocate human resources, tax revenue, and water for the management of community forests and other natural resources in California.
Richard E. Close, Phu V. Nguyen, and J. James Kielbaso
Abstract. This study provides a profile comparison of several tree growth, phenology, and site characteristics. The comparisons are between sugar maple trees in a forest stand and those in tree lawns on urban streets, both sites within 2 km on the Michigan State University campus in East Lansing. Sampled trees are from a stratified random group of healthy sugar maples. The study reports on significant terminal growth differences and much earlier leaf drop from the urban street site. Site soil moisture, air temperature, leaf temperature, relative humidity, and vapor pressure deficit were all significantly less favorable along streets, as was soil bulk density. Soil pH and the foliar nutrients N, K, Ca, Mn, B and Na were significantly less favorable along streets. The net effect of these urban conditions is a slow growing, restricted, low-density root system. This, in combination with prolonged water stress and high atmospheric demand, producing chronic water deficits in the tree crown, results in low vitality and reduced growth rates in the street trees.
Edward F. Gilman
Abstract. No roots of live oak (Quercus virginiana) or sycamore (Platanus occidentalis) went through BiobarrierTM during a 3-year period after planting. Most roots on both species without a barrier were located in the top 30 cm (12 in) of soil, and root number decreased with increasing soil depth. Roots were located at deeper soil depths beyond the Biobarrier. The roots 15 cm (6 in) from the Biobarrier were mostly 30 to 45 cm (12 to 18 in) below the soil surface. Eighty percent of oak roots and 72% of sycamore roots greater than 3 mm in diameter 0.9 m (3 ft) from the trunk without a barrier were in the top 30 cm (12 in) of soil, whereas, only 42% (oak) and 38% (sycamore) of roots were in the top 30 cm (12 in) for trees with the root barrier. Biobarrier forced roots deeper in the soil but in the high water table soil in this study, many roots returned to the soil surface by the time they had grown 1.2 m (4 ft) away from the barrier.