title: Is bark pH more important than tree species in determining the composition of nitrophytic or acidophytic lichen floras?
abstract: 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.
authors.affiliation: Alterra, Landscape Center, POB 47, 6700 AA Wageningen, Netherlands.
authors.forename: L
authors.initials: L
authors.lastname: Spier
authors.forename: H
authors.initials: H
authors.lastname: van Dobben
authors.forename: K
authors.initials: K
authors.lastname: van Dort
mesh_terms: D000393:Air Pollutants / Q000032:analysis; D004784:Environmental Monitoring; D004787:Environmental Pollution; D005163:Factor Analysis, Statistical; D031661:Fraxinus / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008011:Lichens / Q000502:physiology*; D015999:Multivariate Analysis; D009426:Netherlands; D009584:Nitrogen / Q000378:metabolism; D024301:Plant Bark / Q000737:chemistry*; D029963:Quercus / Q000737:chemistry; D013045:Species Specificity; D032384:Tilia / Q000737:chemistry; D034403:Ulmus / Q000737:chemistry
chemical_list: D000393:Air Pollutants; D009584:Nitrogen