118 Silvera Seamans: Grassroots Citizen Science in Urban Spontaneous Vegetation al. 2012). The five models of PPSR are contractual, contributory, collaborative, co-created, and colle- gial. The contributory approach, where the public is asked to collect and submit data to a research project developed by a professional scientist/scien- tist associated with an institution, is the model that best describes most citizen-science projects (Shirk et al. 2012). The collegial model is at the end of the PPSR spectrum where there is little to no distinction between participant and researcher, or “expert ama- teurs arguably adopt the traditional role of scientist- as-knowledge-producer” (Shirk et al. 2012). The authors go on to note that although this model is “oſten overlooked or highly critiqued, commit- ted amateurs can make critical contributions that may not otherwise transpire owing to a lack of re- sources, time, skills, or inclinations in the profes- sional scientific community” (Shirk et al. 2012). Despite the admitted contemporary value of this form of scientific inquiry, not much has been written about collegial PPSR, especially contem- poraneously and in an urban context. An excep- tion is Silva and Krasny (2014), who analyzed the monitoring and evaluation strategies employed by civic-ecology organizations in New York City, New York, U.S. The authors found that of the eight non- profits they studied, five used a collegial form of monitoring protocol, meaning that this subset of organizations relied on lay practitioners and not professional scientists to monitor the outcomes of their projects. The collegial approach is not lim- ited to the evaluation phase of a project. Each of the five elements of a PPSR project (i.e., inputs, activities, outputs, outcomes, and impacts), as defined by Shirk et al. (2012), can be conducted in a collegial manner. PPSR projects studying organ- ismal biota tend to skew toward birds, butterflies, and charismatic flora. There are several citizen- science projects that solicit observations of invasive plants (which is sometimes conflated with ‘weeds’) for the purposes of eradication management. Urban Spontaneous Vegetation Most of the modern studies of urban ecology, at least in the U.S., have skewed toward native rem- nants and designed landscapes, but this is changing. The realization that spontaneous, disturbance- adapted vegetation is a perennial feature of urban ecosystems, or the “flora of the future” ©2018 International Society of Arboriculture (Del Tredici 2014), has instigated research of its potential, ecological and otherwise, and spurred advocacy to design with and to preserve this urban flora. This weedy floristic future is neither homogenous nor is it predominantly introduced, at least among woody angiosperms (Del Tredici 2010a) or invasive. Native plant diversity can be high in cities, while exotic species can be locally abundant, neither “broadly nor invasively distrib- uted” (Pickett et al. 2008). Although many cities share some exotic species, floral (and avian) spe- cies richness has not been homogenized globally (Aronson et al. 2014). Spontaneous plants, native and not, are one of the defining characteristics of urbanized landscapes, including vacant lots (Bur- kholder 2012; Cervelli et al. 2013; Del Tredici 2014), and biodiversity studies of this habitat type reveal some benefits of spontaneous vegetation. In two studies, Rega-Brodsky and Nilon (2016; 2017) showed that vacant lots provide beneficial habitat for songbirds. Vacant lots vary in their successional stage; avian species composition and behavior are associated with different types of vegetative structure. For example, bird species abundance and richness were highest on vacant lots with greater tree cover that were in close proximity, within 100 m, to forested areas (Rega- Brodsky and Nilon 2016). The authors pointed out that protecting tree canopy on vacant lots is an effective way to expand bird habitat. In a second paper, shrub density was the primary factor in nesting success for native generalist species, such as American robins, gray catbirds, and north- ern cardinals (Rega-Brodsky and Nilon 2017). From a structural perspective, sites of urban spontaneous vegetation that are composed of grasses, herbaceous annuals and perennials, shrubs, and light tree cover mimic that of early successional forest communities and thus pro- vide similar functions. Early successional forest ecosystems have been shown to have biological and food web diversity (Swanson et al. 2010). In a comparative study of sites of urban spontane- ous vegetation, remnant forest patches, and lawn areas in Halifax, Nova Scotia, Canada, Robinson and Lundholm (2012) found that areas of sponta- neous vegetation had higher habitat potential for plant and invertebrate diversity. Measurements of leaf-area index across sites showed that parcels
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