344 Table 5. Damage Descriptions for urban forest health monitoring. Variable Instrument Units Damage—presence Field manual description Canker or decay; wound or crack; borers or bark beetles; stem-girdling roots; topping or poor pruning; excessive mulch; dead or dying branches; leaf chlorosis or necrosis; evidence of defoliation; vines in crown; root conflict with sidewalk; crown conflict with utility wires; improper planting urban forests in Wisconsin are estimated to remove approxi- mately 7,050 tons (6,400 metric tons) of pollution per year with an associated annual value of approximately $36.3 million. Pol- lutant removal rate was greatest for ozone (O3) followed by particulate matter less than 10 m, nitrogen dioxide, sulfur di- oxide, and carbon monoxide. Structural Value The urban forests of Wisconsin provide significant social and environmental benefits to the people of Wisconsin. In addition to the functional values described previously, the estimated struc- tural value of Wisconsin’s urban forest is approximately $17 billion. Health Overall, Wisconsin’s urban forests are healthy. Health indicators such as crown dieback, density, and damage reveal only a few issues of concern. Populus tremuloides showed a relatively high average dieback. Coupled with its borderline average crown den- sity, it appears that the species is not doing very well in Wis- consin’s urban forests. More investigation is needed as to wheth- er hypoxylon canker, a common disease of P. tremuloides, is associated with this dieback. Potential Value Loss Resulting from Invasive Pests and Diseases The risk of Asian longhorned beetle to Wisconsin’s urban forest is an estimated loss of $8.0 billion in structural value or 60.2% of all urban trees in the state. The risk of gypsy moth, already present in Wisconsin, is an estimated loss of $960 million in structural value. Finally, the emerald ash borer can kill many species of ash trees and has been detected in states adjacent to Wisconsin. The potential urban risk to this borer in Wisconsin is $2.4 billion or 12.5% of the urban forest tree population. CONCLUSION Urban tree management, just like timber management that uses FIA data, is executed at the local scale (community or stand). Policy and planning decisions involving forest lands are aided by state, regional, and national databases, which are, in part, popu- lated with data collected by the FIA/FHM programs. Similarly, wide-scale urban forest inventories and assessments should gather data at a comparable scale. Quantifying magnitude, com- position, and condition of the urban forest will aid in compre- hensive planning and policies. Identifying changes in species composition, cover types, and presence of invasive species will provide insight to maintain sustainable urban forest systems. Basic metrics, like canopy cover, biomass, and leaf area, can be translated into ecosystem services and values (e.g., carbon se- questration, air pollution removal) of a state’s (or the nation’s) urban trees. Long-term monitoring data on rates of change in and around urban areas are critical to developing management plans to sus- tain urban forest health and cover at the local, regional, and national scales. Health monitoring information can be used to detect or determine what factors are leading to changes in urban forests. Thus, regional and statewide management plans can be developed to help offset the undesirable forces of change. In addition, with accurate data on rates of change, accurate plans for sustaining or enhancing forest cover can be developed. Through continual monitoring, these plans can be updated to sustain urban forest health and consequently environmental qual- ity and human health in urban and urbanizing areas. Comprehensive and strategic policies must be based on accu- rate baseline and trend data. The large-scale data generated through the methods described here will assist policy and man- agement decisions at the regional and state levels and influence actions on a local scale. Basic data collected, like species, com- position, biomass, and leaf area, will be used to incorporate urban vegetation within environmental regulations. National mandates like the Clean Air Act and the Clean Water Act are beginning to recognize the contributions of trees and vegetation to improved resource conditions. For example, state implemen- tation plans may now include trees as a voluntary measure to improve air quality (U.S. EPA 2006). In addition, there are sev- eral other environmental programs in which urban trees could make a contribution to improving environmental quality (e.g., Total Maximum Daily Loads and Stormwater Program for Mu- nicipal Separate Storm Sewer Systems of the Clean Water Act; and several proposed climate change programs) (Nowak 2006). Large-scale data that describe the current and changing forest condition, composition, and extent of the urban forest will aid Table 6. Advantages and issues of concern related to the proposed method for statewide collection of urban forest inventory data. Advantages Large-scale monitoring of forest structure, functions, and health issues Standardized data and collection protocols with national FIA/FHM program Broad picture of urban forest over state/multistate regions Long-term data on rates and patterns of change Annual updates Plot layout consistent with national plot layout in forests for comparative purposes Data collection includes variables collected in forests for comparative purposes FIA/FHM forest inventory and analysis/forest health monitoring. ©2008 International Society of Arboriculture Issues May need plot intensification for increased precision May miss local variables of concern Need adequate analysis staff for timely reporting of data Long-term commitment to remeasure Only a fraction of the total plot population is measured each year Forest subplot design is inefficient for urban areas Some forest variables are not used in urban forest analyses Cumming et al.: Urban Forest Health Monitoring
November 2008
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