260 Roman et al.: Monitoring Young Tree Survival with Citizen Scientists and as Tree Checkers becomes an expected activity for every Tree Tenders group (i.e., staff have pushed for participation more strongly in recent years). The overall 2017 survival was the same for both intern and volunteer data (91%), and interns and volunteers agreed on mortality status for 96% of trees recorded in common (Table 3). For crown vigor, both crews reported that the vast majority of trees were in vigor classes 1 and 2, and volunteer-reported vigor was within one class of intern-reported vigor for 90% of trees recorded in common. Trunk circumference from volunteers was within 2.54 cm of intern val- ues for 62% of trees recorded in common; different circumference values were generally attributable to different heights used. Data consistency levels needed for urban forest management are not necessarily as high as data consistency needs for scientific research (Roman et al. 2013; Bancks et al. 2018). For instance, in this case, mortality and vigor class agreed for the vast majority of trees, and trunk circumference agreed generally within 2.54 cm, but not at the level of inter-field crew agreement required for scientific research with the Forest Service's Forest Inventory and Analysis program (U.S. Forest Service 2016b). These findings suggest that volunteer and intern data quality for vigor and trunk circumference are adequate for PHS needs, but perhaps not sufficient for rigorous research. For instance, the volunteer- produced data should not be used for regression models of factors that predict stem growth, but could be used for rough reporting of typical tree size the first summer after planting. Volunteer mortality observations would be more suitable for research applications, particularly if consistency levels can be raised closer to 99% (the acceptability threshold for mortality consistency in Urban Forest Inven- tory and Analysis, U.S. Forest Service 2016b). The mortality consistency rates for volunteers in Roman et al. (2017) was 99.9%; those citizen scientists had more training hours compared to Tree Checkers but also encountered fewer dead trees. Additional time devoted to training, or different training techniques, could potentially produce higher consistency levels (Starr et al. 2014; Bancks et al. 2018). Future trainings will emphasize that standing dead trees should have completely dead crowns (i.e., a nearly-dead tree with only a few leaves would be classified alive), and dis- cuss how to treat situations in which the main stem is dead but living suckers have emerged at the base. Mulch classification was reported to be the same category for 55% of trees recorded by both interns and volunteers, the lowest consistency level reported in Table 3. Consistency levels for other stewardship variables (presence/absence of weeds/trash, inade- quate water, bark damage, broken branches, suckers/ sprouts, and buried root flare) are not reported here because of concerns regarding how those variables were interpreted and recorded by field crews. We sug- gest several possible explanations for challenges with recording stewardship variables: 1) with subjectivity involved in most of these observations, some crews may be rating trees more harshly; 2) some volunteers may have recorded the circumstances as they leſt the tree (i.e., aſter doing maintenance) rather than how they found the tree (as instructed during training), and may have been more focused on doing mainte- nance than recording it; 3) some of the stewardship variables are inherently ephemeral, so recording this information on different days could produce different observations; and 4) inconsistent notation (e.g., yes/ no, blank/check mark) by volunteers using paper data entry. Overall, it is apparent that improved training is needed to produce consistent results with the stew- ardship variables, and the authors have not reported findings for most stewardship variables because the interpretations are unclear. Learning from these Table 3. Monitoring findings comparing overall volunteer-collected data (n = 707, convenience sample) to intern-collected data (n = 198, random sample), and tree-by-tree consistency for the trees observed by both field crews (n = 178). Blank entries were omitted from all summary data. Variable Survival Crown vigor Trunk circumference Mulch Volunteer result 91% 74% in classes 1 & 2 n/a 40% good ©2018 International Society of Arboriculture Intern result 91% 84% in classes 1 & 2 n/a 34% good Tree-by-tree consistency 96% agreement volunteer vigor within 1 vigor class of interns for 90% of trees 62% within 2.54 cm 55% agreement
November 2018
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