Arboriculture & Urban Forestry 34(6): November 2008 Table 2. Shrub information collected for the UFORE Model. Variable Description Species code Average height of mass Percent area Percent shrub mass missing UFORE Urban Forest Effects. Species code from standard list currently containing over 10,000 tree and shrub species Where mass is a group of shrubs species or genera of similar height (ft or m) Percent of total shrub cover on plot occupied by shrub mass Percent of shrub mass volume (height × ground area) that is not occupied by leaves; estimated to nearest 5% substantially reduce the field work by decreasing the number of trees measured, but less information on trees will be attained. Woody plants that are not 30.5 cm (12 in) in height are con- sidered herbaceous cover (e.g., seedlings). Shrub masses within each plot are divided into groups of same species and size, and for each group, appropriate data are collected (Table 2). Tree variables (Table 3) are collected on every measured tree. Field data are collected during the in-leaf season to help assess crown parameters and health. More detailed information on plot data collection methods and equipment can be found in the i-Tree User’s Manual (i-Tree 2008). Leaf Area and Leaf Biomass Leaf area and leaf biomass of individual open-grown trees (crown light exposure [CLE] of 4 to 5) are calculated using regression equations for deciduous urban species (Nowak 1996). If shading coefficients (percent light intensity intercepted by foliated tree crowns) used in the regression did not exist for an individual species, genus or hardwood averages are used. For deciduous trees that are too large to be used directly in the regression equation, average leaf area index (LAI: m2 leaf area per m2 projected ground area of canopy) is calculated by the regression equation for the maximum tree size based on the appropriate height–width ratio and shading coefficient class of Description the tree. This LAI is applied to the ground area (m2) projected by the tree’s crown to calculate leaf area (m2). For deciduous trees with height-to-width ratios that are too large or too small to be used directly in the regression equations, tree height or width is scaled downward to allow the crown to the reach maximum (2) or minimum (0.5) height-to-width ratio. Leaf area is calculated using the regression equation with the maximum or minimum ratio; leaf area is then scaled back proportionally to reach the original crown volume. For conifer trees (excluding pines), average LAI per height- to-width ratio class for deciduous trees with a shading coefficient of 0.91 is applied to the tree’s ground area to calculate leaf area. The 0.91 shading coefficient class is believed to be the best class to represent conifers because conifer forests typically have ap- proximately 1.5 times more LAI than deciduous forests (Barbour et al. 1980) and 1.5 times the average shading coefficient for deciduous trees (0.83; see Nowak 1996) is equivalent to LAI of the 0.91 shading coefficient. Because pines have lower LAI than other conifers and LAI that are comparable to hardwoods (e.g., Jarvis and Leverenz 1983; Leverenz and Hinckley 1990), the average shading coefficient (0.83) is used to estimate pine leaf area. Leaf biomass is calculated by converting leaf area estimates using species-specific measurements of grams of leaf dry Table 3. Tree variables collected for UFORE analysis with associated reason for data collection. Variable Tree ID Unique tree number Distance (ft/m) and direction (degrees) from plot center or TMPz Species codey (A, C, E, S, V) Number of dbhs recordedy Dbhy (C, S) Dbh measurement height Total heighty (A, C, E, S, V) Height to crown basey (A, S, V) Crown widthy (A, S, V) Percent canopy missingy (A, S, V) Diebacky (C,E, S) Percent impervious beneath canopy (H) Percent shrub cover beneath canopy (H) Crown light exposurey (C, S) Distance (ft/m) and direction (degrees) to space-conditioned residential buildingsy (E) Street tree Tree status Required for UFORE analysis. Variable used to assess: A air pollution removal; C carbon storage/sequestration; E energy conservation; H hydrologic effects; S structural information; V VOC emissions. UFORE Urban Forest Effects. zRequired for permanent reference of plot. y ©2008 International Society of Arboriculture Used to identify and locate trees for future measurements; TMP is tree measurement point (Table 1) Species code from standard list currently containing over 10,000 tree and shrub species For multistemmed trees Diameter at breast height (in/cm) for all recorded stems Recorded if dbh is not measured at 1.37 m (4.5 ft) Height to top of tree (ft/m) Height to base of live crown (ft/m) Recorded by two measurements: N-S (north–south) and E-W (east–west) widths (ft/m) The percent of the crown volume that is not occupied by leaves; two perpendicular measures of missing leaf mass are made and the average result is recorded; recorded to nearest 5% Percent crown dieback to nearest 5% Percent of land area beneath entire tree canopy’s drip line that is impervious Percent of land area beneath canopy drip line that is occupied by shrubs Number of sides of the tree receiving sunlight from above; used to estimate competition and growth rates Measured for trees at least 6.1 m (20 ft) tall and within 18.3 m (60 ft) of structures three stories or less in height Y/N; used to estimate proportion of population that is street trees Indicates if tree is new or removed from last measurement period 349
November 2008
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