Arboriculture & Urban Forestry 36(6): November 2010 exotic vegetation (arriving via means other than encroachment), and encroachment elements (e.g., waste, lawn extensions, unau- thorized pathways, or invasive yard plants). Within each 0.5 m × 0.5 m quadrat sampled, the authors of the current study recorded the percentage cover of the quadrat of each of these components visible at 30 cm above the ground, according to the Braun-Blan- quet (1932) cover-abundance scale. The scale assigns a number, or code, to each forest floor component, ranging from 0 to 6 (Table 1). Table 1. Braun-Blanquet (1932) abundance-cover scale. Code 0 1 2 3 4 5 6 Scale 0% <1% 1%–5% 6%–25% 26%–50% 51%–75% 76%–100% The frequency in which encroachment occurred was calculated by counting the number of times one type of encroachment appeared within the quadrat, no matter what percentage of the quadrat it covered. The sample design was perfected during the pilot study to capture the breath and depth of encroachment activities under different boundary treatments prevalent in Ontario (McWilliam 2009). Boundary treatments included: no boundary treatment; municipal boundary post; mown grass strip; mown grass strip and path; and fence, fence with mown grass strip, fence with mown grass strip and path, fence with gate, fence with gate and mown grass strip, and fence with mown grass strip and path. Eleven 0.5 m × 0.5 m quadrats were sampled at two-meter intervals along five transects placed perpendicular to, and equal distance along, property boundaries. From the prop- erty boundary, transects extended 20 m into forest edges. The 20 m transect length was developed from the results of the pi- lot study that indicated the majority of encroachment occurred within 20 m of forest borders. The first and last transects were placed one meter from neighboring property boundaries to re- duce the risk of recording neighboring encroachment. This design resulted in 55 samples per site, for a total sampling intensity of 930 transects and 10,225 samples (Figure 2). Care was taken to record only encroachment associated with adjacent study residents. For example, cut trees were not recorded because resident-cut trees could not be distin- guished from municipally-cut trees. In addition, evidence of old dumps, rock piles, and old fencing, were not recorded as they may have been from previous agricultural land uses. Categories of encroachment were developed in order to analyze the significance of different encroachment behav- iours within the forest edge. Categories of encroachment were developed from the types and spatial patterns of en- croachment in forest edges in relation to yard activities and patterns revealed in the pilot study (McWilliam 2009). Mu- nicipal forest managers, bylaw enforcement officers, and ca- sual conversations with residents verified these behaviors. Behaviors identified include: 1) waste disposal, 2) yard ex- tension, 3) forest-recreation, 4) response to forest encroach- ment, and 5) yard plant invasions. Disposal behavior results in residence-related waste dumped in forest edges. Yard extension Figure 2. Quadrat/Transect sampling design for one study site. encroachment includes any extensions of private yard-related land uses within the public forest edge. Forest recreation en- croachment includes types of encroachment that result in private, forest recreation-related facilities. Yard plant invasion encroach- ments result in garden plants growing within the forest edge. Ex- otic plants growing in the forest edge, but not typically grown in residential gardens, were not included within the encroach- ment category. Residential encroachment in response to forest encroachment refers to encroachment activities responding to the forest encroaching into yards (e.g., forest vegetation or wildlife). Data Analysis A null hypothesis of uniform distribution within the forest of all encroachment traces, encroachment behaviors, and by boundary treatments was tested using a Kolomogorov-Smirnov test. The number of encroachment areas (frequency) and the percentage of the sampled forest floor covered by each area of encroachment were calculated for all encroachments, as well as by type and behavior of encroachment. In addition, an indicator of the sig- nificance (or of the total area covered by encroachment) per site was calculated by multiplying the mean frequency by the mean Braun-Blanquet (1932) abundance cover scale. For example, if a yard extension encroachment trace was sampled three times in a site (i.e., in three different quadrats) and covered a mean of 75% to 100% of the quadrats (Braun-Blanquet cover scale of 6), then the indicator of encroachment significance for this site would be 18. RESULTS What were the prevalence, mean frequency and per- centage cover of encroachment types and behaviors? Evidence, or traces, of encroachment were recorded in 184 of 186, or 99% of sites. Encroachment incidences numbered 4,422 and were recorded at a mean frequency of approximate- ly 23 traces (evidence of encroachment within quadrats) per study site. Encroachment traces covered on average 26% to 50% of the sampled area. Twenty-nine types of encroachment were sampled. Table 2 lists the frequency of encroachment by type and behavior. Encroachment types suggest encroachment activities are closely associated with yard activities, primarily taking place during the growing season, but stretching into the autumn months after leaf drop. The presence of Christmas trees indicates a small amount of encroachment also occurs in winter. Waste disposal and yard extension were the most com- monly recorded encroachment behaviors. Waste disposal types of encroachment accounted for 59% of encroachment events ©2010 International Society of Arboriculture 255
November 2010
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