Arboriculture & Urban Forestry 46(1): January 2020 surfaces (Berland 2012; McGee et al. 2012; Alonzo et al. 2016; Song et al. 2016; Locke et al. 2017). Com- plementary field-sampled “bottom-up” studies, while providing specifics about tree species, age, and condi- tion, typically sample and assess limited areas because field measurements are costly and it is diffi- cult to obtain access to generally private urban forest properties (Wiseman and McGee 2010; Alonzo et al. 2016). Therefore, few studies have addressed the effects of specific policies on urban tree cover based on detailed field measurements (Landry and Pu 2010; Roman et al. 2014). Increased new housing construction within the area of northern Virginia near Washington, D.C., USA, generally follows the approach of replacing old houses rather than expanding urban boundaries. In Falls Church, Virginia, redevelopment is escalating, 13 with existing houses being replaced by larger ones (City of Falls Church 2005), and most of the city for- est is on private property (Walker 2015). An i-Tree ecosystem analysis (i-Tree 2017) based on a random- ized field sample of public and private plots recently completed for Falls Church estimated 35% canopy cover overall (Wiseman and King 2012); a similar study evaluated street trees (Wiseman and Bartens 2012). However, neither of these assessments pro- vided the kind of information necessary to evaluate, at the plot level, the city’s existing policies that regu- late canopy cover on private land. Municipal management of trees is done less often on private property than on public lands (Conway and Urbani 2007), and can be difficult (Conway 2016), particularly in states with strong private prop- erty rights. However, in Falls Church the residential Table 1. Lot-scale summary of urban forest data for trees on 21 lots in Falls Church, Virginia. Nonoverlapping canopy cover (cover), basal area (ba), trees per hectare (tph), quadratic mean diameter (qmd), and total above/belowground carbon (C) were calculated for inventory Time0 (including trees slated for removal as well as all others on the lot), Time1 (trees preserved and newly planted at time of redevelop- ment), and Time2 (field inventory 1–18 years after redevelopment). The variable period is the number of years between Time1 and Time2 inventories; Time0 was generally one year less than Time1. % Canopy cover Lot 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Min Max Lot area Period (m2 ) 1,551 855 1,213 1,540 1,707 1,176 687 639 970 855 584 1,091 1,297 582 994 972 1,100 1,439 790 1,229 1,008 582 1,707 Mean 1,061 SD 325 (yr) 11 1 10 8 9 6 7 8 15 11 6 14 3 11 12 14 5 9 13 18 1 1 18 9 5 Cover0 53 80 35 49 56 82 64 80 41 28 3 51 85 55 44 8 44 19 62 80 77 3 85 52 24 Cover1 7 28 32 0 48 50 64 0 0 0 2 43 30 5 30 0 36 1 5 15 11 0 64 19 20 Cover2 22 29 41 28 63 56 75 7 51 29 13 58 33 26 51 6 43 13 35 59 14 6 75 36 20 Basal area (m2 Ba0 18.7 19.9 11.1 22.0 13.2 50.1 14.9 31.2 6.9 10.4 1.0 16.1 31.4 11.3 13.8 2.7 19.4 4.2 16.7 31.9 24.1 1 50 18 12 Ba1 1.8 8.0 /ha) Ba2 5.8 8.5 9.7 13.1 0.1 4.0 11.6 17.8 32.4 36.8 15.0 17.1 0 0.8 7.9 2.7 0.1 0.1 0.7 12.6 17.8 5.2 0.6 6.0 3.7 Trees per hectare Tph0 109.6 175.5 49.5 58.4 210.9 221.2 14.6 140.8 41.2 140.4 2.5 119.9 229.2 316.1 86.0 9.6 19.0 110.6 0.1 0.7 14.8 19.9 0.3 1.0 1.5 6.8 4.6 18.4 3.3 0 32 6 8 3.7 1 37 10 9 92.6 181.8 62.5 101.3 366.1 267.8 15 366 147 94 Tph1 96.7 128.7 65.9 279.2 246.0 144.6 58.2 46.9 185.5 105.3 308.4 412.5 84.8 171.9 231.3 185.2 163.7 111.2 113.9 268.5 89.3 47 413 167 95 Tph2 96.7 128.7 65.9 279.2 246.0 144.6 58.2 46.9 185.5 105.3 308.4 412.5 84.8 171.9 231.3 185.2 163.7 111.2 113.9 268.5 89.3 47 413 167 95 Quadratic mean diameter (cm) Qmd0 47 38 53 69 28 54 114 53 46 31 10 30 36 41 40 19 37 29 46 33 34 10 114 42 21 Qmd1 16 28 43 3 25 53 57 3 3 3 5 20 28 7 23 3 34 6 10 15 22 3 57 19 17 Qmd2 28 29 50 14 30 57 61 15 23 18 10 23 30 17 32 7 39 13 27 30 23 7 61 27 15 C0 36.6 24.8 18.0 46.3 33.2 77.2 15.6 28.6 7.7 8.4 0.2 18.8 51.1 8.6 17.1 2.2 26.3 6.0 18.9 54.8 33.3 0 77 25 20 Total carbon (Mg/ha) C1 2.4 7.5 16.3 0 30.7 50.9 15.6 0 0 0 0.1 14.7 8.8 0.2 10.3 0 19.8 0.2 0.9 4.4 3.9 0 51 9 13 C2 8.1 7.9 22.8 4.1 42.8 58.6 18.0 0.4 7.3 1.8 0.7 21.6 10.0 2.0 21.5 0.4 28.0 1.5 6.7 22.6 4.1 0 59 14 15 ©2020 International Society of Arboriculture
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