Arboriculture & Urban Forestry 34(6): November 2008 Table 3. Urban forest health monitoring variables to describe trees. Variable Instrument Tree number Tree location in plot Tree status Cause of death Species Diameter at breast height Height to diameter if not 4.5 Length of tree (height) Height to live crown Distance from tree to buildings UFORE Urban Forest Effects Model. were collected to describe plot, trees, crowns, and damages. Within each of these groupings, specific variables are collected (Tables 2–5). Data Analysis Data are analyzed using the UFORE Model. The UFORE model was developed to help managers and researchers quantify urban forest structure and its functions (Nowak and Crane 2000). UFORE is designed to use standardized field data from ran- domly located plots and local hourly air pollution and meteoro- logic data to quantify urban forest structure and numerous urban forest effects for cities around the world. The model has been adapted to use statewide data and general estimates for structural value (Nowak et al. 2002), air pollution removal (Nowak et al. 2006), carbon storage and sequestration (Nowak and Crane, 2002), risk to certain pests and diseases (Nowak et al. 2001), and building energy conservation (Nowak et al. 2006a, 2006b, 2006c, 2007a, 2007b). Advantages and Disadvantages of the Data Collection Approach The proposed national urban forest health monitoring system has been developed to meet the needs of state and federal urban resource managers for data and analysis of the structure, func- tion, and health of the urban forest. This program, which is designed to provide data and information at the state, regional, and national scale, is not designed to provide information at the local or city scale because there will be too few plots at this scale to provide adequate estimates. Plots at the local scale can be augmented with additional plots to provide desired accuracy of data estimates. Although not readily applicable at the local scale, this national program has advantages related to state and national policies and planning, but also has limitations as outlined in Table 6. Instrument Units RESULTS: WISCONSIN’S URBAN FOREST Data from 139 field plots located within the urban areas of Wisconsin were analyzed in this pilot project conducted by the U.S. Department of Agriculture, Forest Service, in partnership with the State of Wisconsin. Urban areas were designated using the 1990 census definition (U.S. Census Bureau 2002). Data from this statewide urban inventory has yielded interest- ing and useful information. Quantitative descriptions of struc- ture, function, value, and health will assist state and federal resource managers to prioritize and target funding and staffing to maximize benefits of the urban forest for the public. The fol- lowing is a summary of results from the Wisconsin pilot (Cum- ming et al. 2007). Structure A total of 80 different tree species were identified in the urban areas of Wisconsin. These species represent 31 genera and 17 plant families. They are fairly diverse with no one species com- prising more than 8% of the existing population overall. The Acer and Fraxinus genera, however, combine for 30% of all trees in urban Wisconsin. Given the potential risk to Acer from the Asian longhorned beetle and Fraxinus from the emerald ash borer, urban tree planting efforts in Wisconsin should consider shifting away from these genera to other suitable genera to avoid potential large-scale losses from exotic invasive beetles that exist within the United States. Functions Carbon storage by Wisconsin’s urban forest is estimated at 6.7 million tons (6.1 million metric tons). The species that are esti- mated to sequester the most carbon annually are Acer negundo (7.2% of the total annual sequestration), Fraxinus pennsylvanica (7.1%), and Quercus macrocarpa (5.4%). Annual carbon se- questration by urban trees is valued at $8.1 million per year. The Table 4. Urban forest health monitoring variables to describe crowns. Variable Crown light exposure Crown position Crown density Crown dieback Foliage transparency Foliage absent Field manual description No full light; top or one side; top + side or two sides; top + two sides; top + three sides; top + four sides Field manual description Superstory, overstory, understory, open canopy, undefined Field manual description 5% classes ranging from 0 (no crown) to 100% Field manual description 5% classes ranging from 0 to 100% (crown dead) Crown diameter—two directions Tape measure Field manual description 5% classes ranging from 0 (full crown) to 100% (few leaves present) Field manual description 5% classes ranging from 0 to 100% Feet ©2008 International Society of Arboriculture Field manual description Field manual description Field manual description Field manual description Field guides Diameter tape Tape measure Clinometer Clinometer Tape measure Units Number Map Live, dead, removal, missed live tree, missed mortality tree, no history Insect, disease, fire, animal, weather, vegetation, unknown/other, human, physical UFORE species codes Inches Feet Feet Feet Feet 343
November 2008
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