254 MacFarlane: Quantifying Urban Saw Timber lower Michigan, U.S. using systematic inventory procedures across different urban land types and landownerships (both public and private land). Motivation for this research arose from an immediate need to address economic losses associ- ated with an abundance of dead and dying street, park, and backyard trees killed by emerald ash borer in southeastern lower Michigan and a general desire to comprehend the po- tential for recovering urban saw timber. METHODS Study Area The study area was comprised of urban portions of 13 coun- ties in southeastern lower Michigan (Table 1, listed in de- scending order of urban land cover), which constitute the core 13 counties quarantined by the Michigan Department of Ag- riculture to control the spread of emerald ash borer (the beetle has since spread beyond this region). A statewide land use/ land cover (LULC) classification system (IFMAP, MDNR 2003) was used to define urban areas in the 13-county region. Four of 37 IFMAP classes were deemed to represent an “ur- ban” condition: (1) low-intensity urban; (2) high-intensity urban; (3) roads/paved (which includes areas appurtenant to roads and large paved areas such as parking lots); and (4) parks and golf courses; the first three explicitly comprise urban types in IFMAP and the last was added to represent developed greenspace appurtenant to urban land use. The remaining IFMAP classes were combined into one “nonur- ban” stratum that was not considered part of the potential sample space (Table 1). For this study, only roads and paved areas associated with urban areas were of interest; wood from trees associated with other roads and paved areas (e.g., roads traversing farm fields) was not of interest. The fraction of all roads and paved areas that were urban, as opposed to other roads, was approximated as proportional to the total land area that was under high-intensity and low-intensity urban land use (Table 1). Thus, the total urban land area was estimated for each county as the sum of high- and low-intensity urban land use, parks and golf courses, and “urban” roads and paved areas (Table 1). Inventory Methods A stratified, multistage sampling technique (Shiver and Bor- ders 1996) was used to assess the quality and quantity of saw timber over different portions of the urban landscape. An accuracy assessment by NOAA CSCC-CAP (2003) sug- gested that IFMAP most accurately represented LULC types when classified map pixels (30 m × 30 m [99 ft × 99 ft]) were aggregated into larger homogeneous blocks (at least 90 m × 90 m [297 ft × 297 ft]). Thus, the grid of Michigan public survey quarter-quarter sections (QQSs) were chosen to define large (402 m × 402 m [1327 ft × 1327 ft]) primary sample units from which representative urban areas could be se- lected. During the first stage of sampling, random QQSs were chosen within the 13-county area. If the randomly selected QQS was composed of a relatively homogeneous block of one of three urban types (high-intensity urban, low-intensity urban, or parks and golf courses), then it was accepted as a sample location; if not, it was rejected. The roads and paved LULC type was excepted because it never formed relatively homogeneous blocks but was a linear network that traversed portions of QQS blocks. Instead, roads and paved areas were sampled within randomly selected blocks dominated by either high-intensity or low-intensity urban areas such that only Table 1. Urban land use composition in 13 counties in southeastern lower Michigan based on a statewide classified satellite image (IFMAP, MDNR 2003). County Wayne Macomb Oakland Genesee Ingham Washtenaw Livingston Monroe Jackson St. Clair Shiawassee Lenawee Lapeer 13-county area Area (ha) Parks and golf 166,482 2.24% 125,359 1.99% 234,912 1.89% 168,203 0.60% 145,169 0.54% 187,041 0.93% 151,581 0.55% 144,466 0.07% 187,313 0.55% 190,407 0.22% 140,056 0.05% 197,129 0.00% 171,666 0.05% 2,209,786 0.77% ©2007 International Society of Arboriculture High-intensity urban 15.29% 8.62% 5.93% 4.06% 3.16% 2.14% 1.77% 2.12% 1.08% 1.20% 1.18% 0.71% 0.40% 3.61% Low-intensity urban 13.17% 10.53% 8.72% 6.69% 3.32% 2.65% 2.26% 2.08% 2.31% 2.02% 1.18% 1.29% 1.18% 4.44% Roads/paved (urban + other) % Urban % Nonurban 5.72% + 14.37% 36.42% 2.13% + 9.01% 1.33% + 7.72% 0.69% + 5.75% 0.33% + 4.70% 0.22% + 4.38% 0.16% + 3.88% 0.20% + 4.60% 0.12% + 3.49% 0.12% + 3.61% 0.09% + 3.90% 0.07% + 3.66% 0.04% + 2.40% 0.51% + 5.82% 23.27% 17.87% 12.04% 7.34% 5.94% 4.74% 4.47% 4.05% 3.56% 2.51% 2.08% 1.66% 9.32% 63.58% 76.73% 82.13% 87.96% 92.66% 94.06% 95.26% 95.53% 95.95% 96.44% 97.49% 97.92% 98.34% 90.68%
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