ARBORICULTURE CONTENTS & URBAN FORESTRY Volume 46, No. 1, January 2020 Formerly the Journal of Arboriculture, 1975 – 2005 (Volumes 1 – 31) Nicholas J. Brazee and Robert E. Marra Incidence of Internal Decay in American Elms ( ) Under Regular Fungicide Injection to Manage Dutch Elm Disease ................................................................................................1 = 0.182). For elms with decay, there was a significantly higher frequency of trees in the lowest decay class (< 25% of the cross section) com- pared to the highest decay class (> 75% of the cross section). The results suggest that the wounding associated with regular fungicide injection does not increase the likelihood of internal decay and that American elms exhibit a low frequency and severity of internal decay. Keywords. Butt Rot; Decay; Risk Assessment; Systemic Fungicides; Urban Forestry. David C. Chojnacky, Emily K. Smith-McKenna, Laura Y. Johnson, John A. McGee, and Cindy C. Chojnacky Evaluating Urban Canopy Cover Before and After Housing Redevelopment in Falls Church, Virginia, USA .........................................................................................................................................12 Abstract. Local governments have created regulations aimed to maintain and increase valuable urban tree cover. The City of Falls Church, Virginia, USA, requires each residential redevelopment to retain or plant enough trees for 20% canopy cover within ten years. To assess whether this goal is being met, we studied 21 Falls Church residential lots redeveloped between 1994 and 2011 where existing houses had been replaced with larger ones. Initial tree inventories and measurements prior to redevelopment were recorded in redevelopment plans. We remeasured preserved and planted trees in a ground survey and modeled tree canopy growth from a periodic tree diameter growth model linked to a model relating tree and crown diameters. Geo- spatial analysis was used to calculate nonoverlapping canopy cover within lots from crown diameter measurements and/or model predictions. We found that the City of Falls Church generally met its 20% canopy cover goal, but that the canopy cover metric alone is insufficient to fully describe urban for- est recovery. Although canopy cover might recover rapidly from planting many small trees, recovery to the larger tree sizes that maximize ecosystem services can take much longer. Our modeling of lot-scale growth from field measurements showed the potential to manage forests using traditional diameter-based forest metrics that would relate results to canopy cover when needed. These forest stand metrics—based on basal area and trees per hect- are—can account for tree size changes masked by the canopy cover metric. Keywords. Basal Area; GIS Buffer; GIS Dissolve; Municipal Tree Ordinance; Municipal Tree Policy; Quadratic Mean Diameter; Urban Forestry. F.D. Cowett and Nina L. Bassuk Street Tree Diversity in Massachusetts, USA .....................................................................................27 Abstract. Pests, disease, and climate change pose major challenges to street tree survival, and diversity in tree species and genera is widely considered to promote the sustainability of municipal street tree populations. Conversely, the lack of sufficient diversity in street tree population was judged a con- tributing factor in the death and removal of thousands of street trees in Worcester, Massachusetts, that state’s second most populous city, due to an infes- tation of the Asian longhorned beetle (ALB, Anoplophora glabripennis). Therefore, reducing the dominance of prevalent street tree species and genera and increasing tree species and genera diversity are considered vital to sustainable street tree management and to the preservation of the ecosystem ser- vices and social benefits that street trees provide. This paper assesses street tree diversity in Massachusetts by analyzing a nonrandom sample of col- lated municipal street tree inventory data stratified by plant hardiness zones. Consistent with results previously found for Connecticut, New Jersey, New York, and Pennsylvania, results in Massachusetts indicate that a relatively small number of species and genera dominate the composition of most ©2020 International Society of Arboriculture Abstract. Fungicide injection is regularly performed to prevent and manage Dutch elm disease (DED) of American elm (Ulmus americana). In an effort to better understand the effects of long-term fungicide injection on tree health, sonic tomography (SoT) and electrical-resistance tomography (ERT) were used to nondestructively determine the incidence and severity of internal decay in the lower trunk of American elms in suburban and urban set- tings. Overall, 253 sonic and electrical-resistance tomograms were generated from 210 American elms. Sampled trees were partitioned into two fungi- cide injection groups: (1) regular injection; and (2) irregular injection or no known history of injection. Among all American elms, the incidence of internal decay in the lower trunk was 30% (63/210) with a mean percent decay, as determined by SoT, of 39%. Based on Chi-square analysis, there were no significant differences in the frequency of elms with decay by injection history (P = 0.799). Mean percent decay was significantly different by dbh class (P = 0.005) and while linear regression demonstrated a positive correlation between percent decay and dbh, most of the variability went unex- plained (R2 Ulmus americana
January 2020
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