To study the pH preference of epiphytic lichens, the bark pH of Fraxinus, Tilia, Quercus and Ulmus trees in
an urban environment was measured using a flat surface electrode. The total number of trees was 253. A
survey was made of the lichens in a 40 40 cm quadrat surrounding the pH measurement point. Our
data analysis using multivariate and univariate statistical techniques indicates that the tree species is the
most important factor influencing lichen colonisation, and that bark pH alone is of less importance. We
hypothesize that the changed pollution climate, with strong decreases in both sulphur dioxide and ammonia concentrations over the past two decades and a concomitant general increase in bark pH, has made epiphytes less sensitive to pH.
To study the pH preference of epiphytic lichens, the bark pH of Fraxinus, Tilia, Quercus and Ulmus trees inan urban environment was measured using a flat surface electrode. The total number of trees was 253. Asurvey was made of the lichens in a 40 40 cm quadrat surrounding the pH measurement point. Ourdata analysis using multivariate and univariate statistical techniques indicates that the tree species is themost important factor influencing lichen colonisation, and that bark pH alone is of less importance. Wehypothesize that the changed pollution climate, with strong decreases in both sulphur dioxide and ammonia concentrations over the past two decades and a concomitant general increase in bark pH, has made epiphytes less sensitive to pH.
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