166 Kulhavy et al.: Comparison of Tree Condition and Value in Texas, U.S. The latest version published by the Interna- tional Society of Arboriculture was Guide for Plant Appraisal (CTLA 2000), incorporating four factors: size, species, condition, and location. Species rat- ings were regionalized for the state of Texas and are described by Dreesen (1994). The CTLA method is useful for determining the collective value of the urban forest in a community. Tree inventory data can be used to determine an average rating value for tree species (Pokorny and Albers 2003), and this value is multiplied by the total trees inventoried to calculate the urban forest value (Petijean et al. 1997). Grande-Ortiz et al. (2012) reviewed the applicabil- ity of the CTLA method and concluded that it was most suitable for street trees, parks, and forests in urban areas, with low difficulty to implement. The CTLA method is mainly for evaluation and does not consider air pollution, energy savings, and other environmental factors. Characteristics for evalua- tion of urban trees with the CTLA method include species, health and aesthetic value, and location. The CTLA method provides more moderate values compared to five other methods (Grande-Ortiz et al. 2008; Grande-Ortiz et al. 2012). Hollis (2012) recommends further evaluation of the micro- site suitability for location in the CTLA methods. There are three commonly used methods for eval- uating biodiversity. Species Richness (S) is the total number of different organisms present and does not take into consideration the proportion and distribu- tion of each species. Simpson index (D) is a measure- ment that accounts for the richness and the percent of each subspecies (horticultural variety) from a bio- diversity sample within an area. This index assumes the proportion of individuals in an area and indicates their importance to diversity. The Shannon–Wiener index (H) is similar to the Simpson index, taking into account subspecies richness and proportion of subspecies within a zone. Of the species diver- sity indices used, the Shannon–Wiener index (H) is the most common (Spellerberg and Fedor 2003). Hermy and Cornelis (2000) developed a method for the general monitoring of the biodiversity in urban parks based on the Shannon–Wiener index. Assessment and monitoring of urban forest health represents a key point for environmen- tal policy and the management of environmental resources. The species composition, age, and size of urban forests have become complex, includ- ©2014 International Society of Arboriculture ing impacts on the benefits derived from, and the economics for, managing urban forests (McPher- son et al. 1997), the decreased size of urban forest patches, the increased isolation of urban forest patches, and the expansion of roads. These factors have negative effects on native biodiversity. Through proper management, these trends can be reversed, or at least slowed. Progress toward urban forest recovery can be measured through the use of eco- logical indicators that correspond to the specific conditions and trends of concern (Noss 1999). Since the completion of the Global Positioning System (GPS) in 1995, the integration of GPS and Geographic Information Systems (GIS) technology has expanded rapidly for ecological and conserva- tion applications. GIS is an information technology with the capacity to retrieve, store, analyze, and dis- play both spatial and non-spatial data (Parker 1988). Using GPS and GIS, trees in an urban area can be inventoried with high efficiency and precision. To determine the current replacement value and forest health condition in the 26 Nacogdoches city parks and the SFASU campus, trees were appraised using the Evaluation of Texas Shade Trees formula (Dreesen 1994) based on the standards of the Coun- cil of Trees and Landscape Appraisers (CTLA 1992; CTLA 2000). Each tree was measured for species, size, condition, growth, structure, insects and dis- ease, life expectancy, and location. Species rich- ness, species evenness, Shannon-Weiner index, and Simpson index were calculated to analyze the biodiversity of the SFASU campus and city parks. METHODS Field Measurement In 26 Nacogdoches city parks and cemeteries and the SFASU campus, each tree >10 cm diameter at 1.4 m in the parks and on campus was located using a Trimble Pathfinder ProXRS® GPS unit to an accuracy of 1 m. The geographic coordinates of each tree along with its attributes were entered into an ArcGIS 10.1 (ESRI, Redlands, California, U.S.) geo- database in the GIS Laboratory, Arthur Temple Col- lege of Forestry and Agriculture, SFASU. Initial tree locations for SFASU were located by Perkins (1996) and updated in 2005 and 2010. City park trees were rated in 2005 and data updated in 2008. For the city parks, trees with a diameter >10 cm at 1.4 m and lo-
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