Arboriculture & Urban Forestry 40(3): May 2014 cated within 30.5 m of a main area of use (pavilions, playgrounds, restrooms) were measured. For SFA- SU, trees were measured in the core part of campus. Tree Value Assessment Mapped trees were evaluated to determine the U.S. dollar value and to calculate biodiversity and health condition using the Texas Shade Tree Valuation Formula (Dreesen 1994) based on the CTLA method (CTLA 2000). The four vari- ables measured were size, species, condition, and location, as used in the following formula: [2] Location where N = value per square inch of cross-sectional areal; USD $75 per 6.5 cm2 , a value of $75 for N was used for this study; Size = cross-sectional area in square inches based on diameter in inch- es at 1.4 m, (DBH)2 times 0.7854; Species Class = 1.0, 0.80, 0.60, or 0.10 depending on the spe- cies; and Condition = percentage of health value. Condition is based on a scale of 1–5 (1 being the lowest) for Trunk, Structure, Crown Development, and Life Expectancy; and a scale of 1–3 for Insects and Disease and Growth. Variable ratings for condition are: • Trunk Condition: sound and solid, 5; missing section of bark, 3; extensive decay, 1 • Growth: vigorous, 3; moderate, 2; poor, 1 • Crown Structure: sound, 5; one major or several limbs dead, broken, or missing, 4; two or more major limbs dead, broken, or missing, 1 • Insects and Disease: no pests, 3; one pest 2; two or more pests, 1 • Crown Development: full and dense crowns with balanced growth, 5; full but unbalanced 3; unbalanced and lacking a full crown, 1 • Life Expectancy: more than 20 years, 5; 15 to 20 years, 3; less than 5 years, 1. Life expectancy was estimated based on species, location, condition variables of the trunk, growth, structure of the crown, presence of absence of insects and diseases, and growing area available. Data for age for In the GIS geodatabase, each tree was calculated in the attribute table for its value as a function of the five variables (value, size, species, condition, and location). Another attribute field was added assuming the rating of the six Condition vari- ables was a 26 out of 26 rating, therefore 100% as the Condition value. The difference between the field-measured value and the tree in optimum health condition value was compared as a mea- sure of loss for the parks and university trees. The central research question was to compare tree health, as measured by condition and species, between the Nacogdoches city park trees and the SFASU campus trees. The overall tree health condi- tion values and the six variables, which determine the condition values (trunk, growth, structure, insect and disease, crown development, and life expectancy), were compared between the two groups. A t-test (alpha 0.05) was conducted on each variable to determine if there was a significant difference between the two. The test applied to all trees in two groups. In addition, the same test was performed on those individual species where 30 ©2014 International Society of Arboriculture Value = N × Size × Species Class × Condition × 167 removal for campus trees were based on the rate of removal for the past 20 years, and for the last 10 years for Nacogdoches parks trees. Smiley and Baker (1988) indicate life expectancy is not easy to determine; however, the CTLA method provides ranges for estimated time of removal. Hollis (2012) indicates the comparative age of a tree and its current life expectancy should be consistent with International Valuation Standards (IVSC 2005). The remaining life expectancy of a tree is part of the Condition factor in Guide for Plant Appraisal (CTLA 2000). For condition, a total score of 26 is 100% of condition (maximum of each variable); the minimum value is 6 out of 26 (23%). These trees did not have visible crown or trunk defects or pest problems; and the growth and longevity were considered optimum for the site. • Location: This value refers to the placement of the plant within the landscape. Since all the trees involved in this evaluation are park or campus trees, this value was 70% of value (Dreesen 1994).
May 2014
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