88 characteristics of respondents is reported in Table 1. Care was taken in order to cover various conditions for administrating the questionnaire, so different temporal windows (from morning to late afternoon) and days of the week were randomly selected. The questionnaires were administered by 17 undergraduate students of the Faculty of Agricultural Sciences of the Univer- sity of Pisa (10 males and 7 females), who volunteered by fol- lowing a short introductory seminar. The interviewers wore a T-shirt, a cap, and a badge of their Faculty, to make them eas- ily recognizable, and to look respectable but no too formal. Table 1. Sample breakdown according to gender, age, edu- cation, and occupational characteristics of respondents (figures represent the responses per category). Variable Gender Age (years) Levels Men Women Total 15-19 20-30 31-50 Over 50 Total Education Occupation Housewife Retired Student Professionalz Manualy Othersx Total 306 184 181 144 110 19 944 32.4 19.5 19.2 15.2 11.7 2.0 100.0 zIncludes white-collar worker, teacher, self-employee, managers, and professionals. yIncludes workmen, unskilled workmen, and craftsmen. xIncludes unemployed. Questionnaire In addition to standard demographic profiles, the standard ques- tionnaire comprised the following items: 1. Do you frequent this garden/boulevard (a) often; (b) sometimes; (c) seldom? 2. Can you recognize differences between this plant (dead) and the other(s) (healthy)? The following options were given: (yes; no; no reply.) 3. What could the cause of the death be? (open question, with a single answer allowed) 4. Are you aware that a diseased/dead tree may collapse and cause injury to people or property? (yes; no; no reply.) 5. Do you have any suggestions to give your administrators concerning the management of public greenery? (open question, with a single answer allowed). Up to junior high school Senior high school Degree/Ph.D. Total n 501 443 944 147 270 276 251 944 79 671 194 944 % 53.1 46.9 100.0 15.6 28.6 29.2 26.6 100.0 8.3 71.1 20.6 100.0 Nali and Lorenzini.: Perceptions of Tree Disease All of the questions were put verbally and the responses were recorded immediately by the interviewer on questionnaire sheets carried on a clipboard. The short and easily understand- able format allowed interviewed people to complete the survey in less than ten minutes, although some people lingered longer to ask questions about our research. All people who accept- ed to collaborate a tulip bulb was given as a sign of gratitude. Statistical Analysis Variability of the socio-demographic characteristics of par- ticipants (gender, age, education and occupation) in relation to their answers was analysed with contingency table [Pear- son chi-square test (χ2 )]. This tests to the data sets to derive quantitative measures that are linked with the answers of re- spondents, have a null hypothesis that the relative frequencies of occurrence of observed events (in this case the responses) follow a specified frequency distribution. The events are con- sidered to be independent and have the same distribution, and the outcomes of each event should be mutually exclusive. The data are divided into k bins and the test statistic is defined as , pected frequency for bin i. The expected frequency is calculated by , where Oi is the observed frequency for bin i and Ei where F is the cumulative distribution function for the distribu- tion being tested, Yu is the upper limit for class i, Yl for class i, and N is the sample size (Snedecor and Cochran 1989). RESULTS AND DISCUSSION Phytopathological Diagnosis Preliminary conventional phytopathological investigations and etiological analysis were performed on tissues (collected in loco) of the paradigmatic trees, in order to ascertain the actual causes of the death. For the systematic classification of fungal pathogens have been used specific scientific texts (Anselmi and Govi 1996; Brown 1982; Goidanich 1975, 1986, 1987, 1994; Tattar 1978) that made it possible, to diagnose, in all cases, fungal root rot caused by Armillaria sp. So, for the aim of this study, the correct answer to the question #3 was “a disease.” If an infectious agent (a pathogenic fungal species) was the actual culprit, we should keep in mind that—especially in urban environments—other predisposing or contributing stress factors may play a role in decline and death of trees, such as drought, air pollution, poor fertility, soil compaction, or insects (Manion 1981). However, the peculiar location of the dead trees (surround- ed by healthy ones) should suggest that “generic” stress factors (such as pollution) could not have been so selective to injure a single tree and to save all the others. Furthermore, age of the trees was not likely a stress factor, as the selected (dead) trees were quite uniform in size and shape to the adjacent, healthy trees. is the lower limit is the ex- ©2009 International Society of Arboriculture
March 2009
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