ARBORICULTURE ARBORICULTU & CONTENTS URBAN FORESTRY Volume 37, Issue 2, March 2011 Formerly the Journal of Arboriculture, 1975 – 2005 (Volumes 1 – 31) www.isa-arbor.com Justin Morgenroth Root Growth Response of Platanus orientalis to Porous Pavements ............................................. 45 Abstract. An experiment was established to determine the effect of porous pavement on underlying root growth. An augmented fac- torial arrangementof pavement profile designs and pavement types was installed and fifty Platanus orientalis seedlings were evenly distributed to control plots or one of four treatments. Treated plots were characterized by either porous or impervious pavement pads measuring 2.3 m × 2.3 m, and underlain by either fine sandy loam or a gravel base and compacted subgrade, reflecting two pave- ment profile designs. Following two growing seasons, root abundance was categorized by diameter and depth. Results suggest root abundance is greater, especially at shallow soil depths, under pavements. Pavements designed with a compacted subgrade and gravel base only exacerbated shallow root growth, though they could decrease total root abundance. Finally, porous and impervious pave- ments affected root abundance and distribution in similar ways, dismissing the use of porous pavements to promote deeper rooting. Key Words. Abundance; Biomass; Diameter; Distribution; Oriental Plan; Permeable; Pervious; Road; Sidewalk; Soil Compaction; Street Tree. P. Eric Wiseman, Joseph W. Hoffman, Susan D. Day, and Terry L. Clements A Syllabus-based Review of Collegiate Arboriculture Course Content in the United States ......... 51 Abstract. The professional skills and expertise demanded of practicing arborists are greater than at any time in the past, and many employ- ers and educators believe that higher education plays a role in educating future professionals in this field. Although recent surveys have identified major instructional topics that are critically important for future arborists, no assessment of whether these topics are being taught in college and university programs is available. The following paper is a syllabus-level assessment of 68 arboriculture courses being taught at U.S. institutions of higher education. The most common instructional topics observed in syllabi of arboriculture courses at both two- and four-year institutions were pruning (85%), disorders (81%), physiology/biology (79%), risks/hazards (79%), and soils/nutrition (75%). Tree planting and tree selection, topics identified by educators and public sector employers in previous studies as among the most important instructional areas, were found only in 74% and 62% of course syllabi, respectively. Safety was mentioned in only 53% of syllabi. Syllabus content was similar at two-year and four-year institutions, although tree identification and arborist certification were mentioned more frequently in two-year institution syllabi. Trends in arboriculture education and implications for employers and professionals are discussed. Key Words. Arboriculture Education; Arborist Training; Course Objectives; Educational Assessment. Christina Staudhammer, Francisco Escobedo, Alicia Lawrence, Mary Duryea, Pete Smith, and Mickey Merritt Rapid Assessment of Change and Hurricane Impacts to Houston’s Urban Forest Structure ......... 60 Abstract. A subsample of 332, 0.06-hectare plots measured during 2001–2002 in Houston, TX, U.S., were relocated and measured in 2008 following Hurricane Ike. These 37 re-measured plots provide a unique opportunity to explore the effects of urbanization and hur- ricanes on the forest structure of coastal urban forests. Statistical analyses of growth, mortality, and in-growth were conducted using plot- and tree-level factors. In total, 305 trees were re-measured, of which 195 (63.9%) still remained on-site and 110 (36.1%) had been removed. Ninety-seven (31.8%) of these trees were determined to be removed due to urbanization and 13 trees (4.3%) were removed due to hurricane impacts. Results show an overall annual net loss in tree numbers and an increase in tree density during the analysis period. Average annual mortality and in-growth rates were 3.9% and 5.3%, respectively. Growth rates were significantly influenced by land cover type, tree stem diameter, crown width, and percent dieback (P < 0.05). Overall, Hurricane Ike resulted in the removal of 4.3% of all trees measured, with removal occurring on six (16%) of the 37 re-measured plots. These initial findings could be used to under- stand changes in forest structure in coastal urban areas, improve estimates of carbon sequestration, and develop management goals. Key Words. Emergency Management; Hurricane Damage; Urban Forest Growth; Urban Forest Mortality. ©2011 | International Society of Arboriculture | ISSN:1935-5297
March 2011
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