Arboriculture & Urban Forestry 40(3): May 2014 Arboriculture & Urban Forestry 2014. 40(3): 165–177 165 Comparison of Tree Condition and Value for City Parks and Stephen F. Austin State University in Nacogdoches, Texas, U.S. David L. Kulhavy, Di Wu, Daniel R. Unger, I-Kuai Hung, and Jianghua Sun Abstract. Trees in landscapes are valued for physical as well as aesthetic benefits and biodiversity. Trees on a university campus and in city parks also help to provide an environment in which students and visitors can study and relax. A critical decision facing urban forest- ers, arborists, and planners involves deciding when an existing tree should be removed and replaced; it is a decision oſten based on an evaluation of the tree’s health, condition, and safety concerns. This project surveyed a total of 3,335 trees with 79 species on the campus of Stephen F. Austin State University (Nacogdoches, Texas, U.S.) and 1,572 trees with 44 species in Nacogdoches city parks. Tree health and replacement values of the two groups were statistically compared, as were the diversities of the two. Finally, the tree health conditions and distributions were spatially analyzed using a geographic information system. Although there was statistical evidence indicating that the campus trees were significantly healthier than the city park trees, neither of their biodiversity status was desirable. It is important to identify and remove trees with extensive wood decay and introduce new species when performing forest maintenance and management. Key Words. Biodiversity; Campus; City Park; CTLA Method; Geographic Information Systems; Hazard Rating; Inventory; Risk Assess- ment; Species Diversity; Texas; Tree Valuation. Trees in the landscape are valued for physical, aes- thetic, and environmental benefits, as well as for their ecological biodiversity. The urban forest in city parks and at Stephen F. Austin State University (SFA- SU), Nacogdoches, Texas, U.S., provides an environ- ment for education and recreation. Critical deci- sions facing urban foresters, arborists, and planners involve deciding whether an existing tree should be removed and replaced based on an evaluation of the tree’s health, condition, and safety concerns as part of a tree maintenance program. Urban areas, with 75% of the population, contain over 3.8 billion trees covering 3.5% of the 48 contiguous United States. In the first national assessment of urban forest resources in the United States (Dwyer et al. 2000), important issues were local scale variation, com- plexity, connectedness of urban forest resources, and changes over time in response to external forces. The methods to calculate tree values vary world- wide (Helliwell 1967; McGarry and Moore 1988; Flook 1996; Asociacion Española de Parques y Jardines Publicos 1999; CTLA 2000; Helliwell 2000; Watson 2002). In the United States, a method authored by the Council of Trees and Landscape Appraisers (CTLA) has been widely used since 1951 (9th edition published in 2000; CTLA 2000) in both the public and private sector due to its flexibility (Nowak et al. 2002). This method is based on a mea- surement of the cross-sectional area of the tree trunk at 1.4 m height (DBH), multiplied by a monetary value per square inch (6.45 cm2 ). This is the maximum value, which is then reduced by factors for species quality, condition, and location in the landscape (0.0 to 1.0 for each factor). The value per square inches based on the cost of the largest commonly available trees (per square inch of trunk cross-sectional area) at regional nurseries. This cost was determined by a regional committee (CTLA 1992; CTLA 2000). The simplified formula of the CTLA method is: [1] Appraised Value = (Trunk Area × Basic Price × Species × Condition × Location) where parameters are multiplied based on area of the cross section of the trunk at 1.4 m in height (Grande-Ortiz et al. 2012). ©2014 International Society of Arboriculture
May 2014
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