Arboriculture & Urban Forestry 39(4): July 2013 Arboriculture & Urban Forestry 2013. 39(4): 189–196 189 Stewardship Success: How Community Group Dynamics Affect Urban Street Tree Survival and Growth Emily Jack-Scott, Max Piana, Blake Troxel, Colleen Murphy-Dunning, and Mark S. Ashton Abstract. Over the last two decades, there has been a substantial increase in street tree plantings across the United States. Many cities have set ambitious planting goals, relying on volunteer community groups to meet them. Existing research demonstrates that community stewardship increases the survival of urban street trees. There is a lack of research, however, on how defining characteristics of community groups affect the survival and growth of the trees they plant. This study explores the significance of community group size (# participants), type (apartment, block watch, church, concerned neighbors, park, public housing, school, and social service), planting longevity (# years active), experience level (# trees planted), and neighborhood (geo-political boundaries). Measured for this study were 1393 trees planted from 1995 to 2007, by 134 groups, through the Urban Resources Initiative’s Community Greenspace program in New Haven, Connecticut, U.S. There was an overall survival rate of 76%. Highest survival and growth was found among trees planted by groups with more planting experience, greater longevity, and more participants. Higher tree survival and growth was observed when trees were planted by groups working in line with their mission (e.g., park groups in parks). Lowest survival and growth was found among yard trees planted by public housing groups. Existing canopy cover and neighborhood percent homeownership had little effect on survival or growth. This research can offer guidance for city managers by suggesting which planting groups require particular assistance in conducting successful, lasting street tree plantings. Key Words. Community Forestry; Connecticut; Mean Annual Growth Increment; Mortality; Percent Live Crown; Planting; Stewardship; Urban Ecol- ogy; Urban Forestry; Volunteer. Urban trees are important features of city infrastructure and are known to improve air quality, ameliorate summer heat island temperatures, lower cooling costs (McPherson et al. 1994), re- duce storm water runoff (Sanders 1984), and increase property values (Anderson and Cordell 1988). They foster neighbor- hood cohesion by attracting permanent homeowners (Burch and Grove 1993; Zhang et al. 2007) and lowering violence and crime rates (Sullivan and Kuo 1996; Troy et al. 2012). Urban trees also boost cognitive development and function in urban children (Wells 2000; Taylor and Kuo 2011), alleviate stress, improve interpersonal relations, and provide spiritual fulfillment (Dwyer et al. 1992). Urban populations feel, on average, very positively toward street trees—most highly valuing their shade, aesthetics, air quality, and noise amelioration (Lohr et al. 2004). Despite increasing requests for tree plantings, canopy cover across U.S. cities is in decline (Nowak and Greenfield 2012). Survival of urban street trees has long been a problem, with survival over 50 years as low as 23% (Foster and Blaine 1978). Urban trees face many obstacles in the urban environ- ment. Generally speaking, ‘shortage of funds’ is cited by half of ecological stewardship groups as their major obstacle (Svendsen and Campbell 2008), and urban foresters are no exception (McPherson et al. 1997). Three recurring biophysi- cal challenges are: 1) insufficient nutrients, 2) lack of water, and 3) vandalism (Black 1978; Beatty and Heckman 1981; Quigley 2004); all of which can be ameliorated by commu- nity and homeowner involvement. It is therefore apparent that in order to augment city-wide canopy cover, urban forest- ers must not only increase the number of new plantings, but also bolster maintenance and survival of existing trees (Luley and Bond 2002; Maco and McPherson 2003; Boyce 2010). Community group participation has proven integral to meeting these planting and maintenance needs (Dwyer et al. 2000; Conrad and Daoust 2008; Greene et al. 2011). Home- owner inclusion in the planting process can lead to higher empowerment (Westphal 2003) and higher ratings of satisfac- tion with street trees (Sommer et al. 1994), greater sense of ownership, and improved stewardship (Black 1978; Pagdee et al. 2006). This is a crucial process, as trees have higher rates of survival when stewarded by local community groups (Boyce 2010). Volunteer motivations for planting trees vary. The most commonly reported motives included: a) improving the aes- thetics and health of the urban environment, b) community service, c) benefiting youth, and d) a love for planting trees (Westphal 1993; Ryan et al. 2001; Moskell et al. 2010). Vol- unteers become deeply committed to not only their worksites, but also to other natural spaces in their areas (Ryan et al. 2001). It is difficult for practitioners to gauge the success of com- munity-driven urban greening projects because progress is of- ten relative for each group (Westphal 2003). Possible indicators of success are longevity (Burch and Grove 1993), sustainability (Florin et al. 1992), and group size (Pagdee et al. 2006; Wag- ner and Fernandez-Gimenez 2009). These can be influenced by the degree to which members of the group relate to the issue, the cohesion of its members around a mission, the support the group receives from the broader base, and lastly, the group’s ©2013 International Society of Arboriculture
July 2013
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