Sustainable urban forests require tree acceptance and support. Two groups of respondents, professionals (working in urban green areas) and individuals (with no professional connection with trees) revealed their attitudes towards trees by assessing statements in a survey questionnaire. Similar general attitude from professionals and nonprofessionals towards the examined benefits and harms related to urban trees was observed. Tree benefits were perceived as much more important than the annoyance they might cause. However, 6% of nonprofessionals found only negative aspects in trees, proving to be arboriphobes. No arboriphobes and no “Tree sceptics” were among the professionals. Around 40% of the respondents in the two groups found the number of trees in the surrounding areas too low. The nuisance caused by trees was seen as more disturbing by younger and lower-educated professionals. Women tended to assess trees as more attractive and as having a stronger influence on socioeconomic contributions than men. Men dominated the “Tree indifferent” group. The attractiveness of trees and their impact on socioeconomic contributions were related to the place of residence and the level of education among the nonprofessionals. The level of education of the nonprofessionals was also connected to being clustered into one of the four abovementioned groups of respondents. A majority of medium and big city dwellers as well as a minority of villagers were in the “Tree liking” cluster.

New, radiatively generated, leading order (LO) quark $\mathrm{}(u,d,s,c,b)\mathrm{}$ and gluon densities in a real, unpolarized photon are presented. We perform a global 3-parameter fit, based on LO Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution equations, to all available data for the structure function $F_2^{\gamma }{(x,Q}^2).\mathrm{}$ We adopt a new theoretical approach called ACOT(χ), originally introduced for the proton, to deal with the heavy-quark thresholds. This defines our basic model [Cornet-Jankowski-Krawczyk-Lorca (CJKL) model], which gives a very good description of the experimental data on $F_2^{\gamma }{(x,Q}^2),$ for both $Q^2$ and x dependences. For comparison we perform a standard fit using the fixed flavor-number scheme $({\mathrm{FFNS}}_{\mathrm{CJKL}}$ model), updated with respect to the previous fits of this type. We show the superiority of the CJKL fit over the ${\mathrm{FFNS}}_{\mathrm{CJKL}}$ one and other LO fits to the $F_2^{\gamma }{(x,Q}^2)$ data. The CJKL model gives also the best description of the CERN LEP data on the $Q^2$ dependence of the $F_2^{\gamma },$ averaged over various x regions, and the $F_{2,c}^{\gamma },$ which were not used directly in the fit. Finally, a simple analytic parametrization of the resulting parton densities obtained with the CJKL model is given.