208 MATERIALS AND METHODS Study Site The study site was the Auburn University campus (32°36’N, 85°30’W). The core campus encompasses approximately 306 ha. The inventory included the managed and landscaped portions of campus, which covered approximately 238 ha. Inventory The method of assessment for this project was a 100% tree in- ventory in an i-Tree Eco compatible form (i-Tree 2010c; i-Tree 2010d). The managed areas of campus were first divided into 99 sections and numbered using spring 2008 aerial photo- graphs courtesy of the City of Auburn (Figure 1). The study area was divided into sections to provide a layout for inven- tory crews to follow and keep track of areas (“bookkeeping”) that had and had not been inventoried. Section perimeters were determined by selecting borders such as streets and side- walks where possible, and natural borders in all other cases so that sections were easily distinguishable. Sections were numbered starting with central campus and moving outward. Martin et al.: 100% Tree Inventory Using i-Tree Eco Protocol taken at 0.3 m from the ground line. Crapemyrtle (Lagerstroemia spp.) was the only species measured at 0.3 m from the ground for all specimens, because the majority of the trees were not measur- able at breast height due to their inherent form. Total tree and bole height were evaluated using a laser hypsometer (either a MDL La- serAce® hypsometer or a Laser Technology, Inc. TruPulse™ 360B rangefinder). Total tree height was determined by measuring from the ground line to the top (alive or dead) of the tree, and bole height was recorded as the height to the lowest branch of signifi- cance. Crown width was determined by taking two measurements from the crown edges at 90 degree angles and averaging them. Data collected were downloaded from the GPS units to a desk- top computer (daily) using the Trimble GPS Pathfinder® v.4.1 and 4.2 software. The ESRI ArcGIS® 9 ArcMap™ Office v.9.3 soft- ware was used for final data presentation. Once all data collection was completed, it was sent to the USDA Forest Service for analysis. Tree Condition Rating Dieback and percent missing crown were determined for each tree. Dieback of branches that appeared to have died from the terminal ends was evaluated by observing all sides of the tree and assigning an overall estimate of the percent dieback. Ranges of <1, 1–10, 11–25, 26–50, 51–75, 76–99, and 100% dieback were used to assign tree conditions of Excellent, Good, Fair, Poor, Critical, Dying, and Dead, respectively. The percent missing, or the amount of the crown that was missing, was determined the same way as percent dieback, by viewing all sides of a tree and estimating the overall percent missing in 5% increments. Missing crowns could be due to impacts such as directional pruning or branches being lost due to damage (e.g., ice, wind). In addition to the i-Tree Eco protocol, an overall condition Figure 1. Aerial photograph of the Auburn University campus in spring 2008. Data Collection All data were collected following i-Tree Eco tree inventory pro- tocol (i-Tree 2010c). Field data were collected by crews consist- ing of 1–3 members. A Global Positioning System (GPS) unit (either a Trimble GeoXM GeoExplorer® 2005 or a Trimble Ge- tripod) was used to collect forest structure data in a data diction- ary. The software used on the GPS units was TerraSync™ oXT GeoExplorer® 2008 series, with an external antenna on a v.2.4. The correct section was identified and the number entered into the collection unit. Total number of stems per tree was recorded and diameter at breast height (DBH) (1.37 m above ground) was obtained using a logger’s diameter tape. Minimum tree DBH to be included in the inventory was 2.54 cm. For multi-stem trees, up to the six largest stems were recorded at breast height. For those trees that could not be measured at breast height, the measurement was ©2011 International Society of Arboriculture rating was assigned as a comparison by assessing all aspects of a tree that were visible, including dieback and missing crown, trunk or limb damage, the presence of insects or dis- ease, visible root damage, and the proximity to infrastructure. The condition rating used was a modification of other rat- ings (Webster 1978; CTLA 2000). The rating scale was: 6 = Excellent condition, 5 = Good, 4 = Fair, 3 = Poor, 2 = Very Poor, and 1 = Dying/Dead. Excellent condition consisted of no missing crown, dieback, visible damage, or disease and pest presence. Good condition constituted <10% dieback, missing crown, visible structural damage, and injury from diseases and pests; whereas a condition rating of Fair had 10%–25%, Poor had 25%–50%, Very Poor had 50%–75%, and Dying/ Dead had >75% of the tree being affected by one or more maladies. The most noticeable (ocular observation) damag- ing factor was used as the deciding reason when assigning the condition rating. To reduce subjectivity, each crew mem- ber would rate tree condition independently, and then all crew members would discuss and arrive at one tree condition rating. To evaluate dieback as a tree condition indicator, the study authors compared the rating to the overall tree condi- tion rating for every tree on campus. To analyze the data, dieback ranges were assigned a numerical value, where <1% = 6, 1%–10% = 5, 11%–25% = 4, 26%–50% = 3, 51%–75% = 2, and 76%–99%, and 100% = 1; and the tree condition ratings used the assigned numbers. For the anal- ysis, trees rated as Excellent and Good by the dieback and overall condition ratings were combined into one group.
September 2011
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