Hallo Krtek,
ich nehme an, es geht dir um die Besiedlung der Baumborke mit Flechten, inwiefern diese vom pH-Wert beeinflusst werden.
Also, auf welchen Substraten mit welchem pH-Wert die größte Anzahl oder Diversität zu erwarten ist?
Ich habe jetzt mal kurz in engl. Sprache gesucht (bark pH lichen) und zwei interessante Untersuchungen gefunden (sehr sehr lang, nicht alles gelesen), von da aus könnte man auch noch weiter suchen.
"Tree and stand level variables influencing diversity of lichens on temperate broad-leaved trees in boreo-nemoral floodplain forests"
https://www.researchgate.net/publicatio ... in_forests
Abstract
Tree and stand level variables affecting the species richness, cover and composition of epiphytic lichens on temperate broad-leaved trees (Fraxinus excelsior, Quercus robur, Tilia cordata, Ulmus glabra, and U. laevis) were analysed in floodplain forest stands in Estonia. The effect of tree species, substrate characteristics, and stand and regional variables were tested by partial canonical correspondence analysis (pCCA) and by general linear mixed models (GLMM). The most pronounced factors affecting the species richness, cover and composition of epiphytic lichens are acidity of tree bark, bryophyte cover and circumference of tree stems. Stand level characteristics have less effects on the species richness of epiphytic lichens, however, lichen cover and composition was influenced by stand age and light availability. The boreo-nemoral floodplain forests represent valuable habitats for epiphytic lichens. As substrate-related factors influence the species diversity of lichens on temperate broad-leaved trees differently, it is important to consider the effect of each tree species in biodiversity and conservation studies of lichens.
Darin zur pH-Messung
Measurement of bark pH
For measurement of pH of bark surface, two small samples of bark (ca. 1.5 cm 2 ) were cut with a knife within each 20 9 20 cm sample plot on both sides of the tree trunk. Bark samples were air dried and stored in paper bags until laboratory analysis. To measure bark pH, a flathead electrode (Consort C532) was used applying a slightly modified technique suggested by Schmidt et al. (2001) and Kricke (2002). Of a solvent (0.01 M KCl), 0.5 ml was dropped in a small Petri dish and a bark sample was placed into the solvent with the outer surface downward to soak only its uppermost part. After a minute of floating, the bark sample was removed and the solvent was slightly shaken off. Then the flathead electrode was pressed against the bark, and the bark pH value was measured during 3 min. In statistical analyses the mean pH of two bark samples from one sample plot was calculated.
"Is bark pH more important than tree species in determining the composition of nitrophytic or acidophytic lichen floras?"
https://www.sciencedirect.com/science/a ... 9110003465
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.
Die Ergebnisse sind also durchaus etwas widersprüchlich. In den letzten Jahrzehnten haben sich die Umweltbedingungen (Luftverschmutzung) betr. einiger Parameter verbessert, die (an sich meist sauren) Borken waren früher noch saurer (durch Umwelteinflüsse), jetzt weniger sauer - aber der Flechtenbewuchs ist nicht immer so, wie man es rein nach pH-Werten oder eingetragenen Nährstoffen vermuten würde.
In einem der beiden Texte stand auch, dass nur extrem saure oder extrem alkalische Borke Flechtenwachstum stark beeinträchtigen/ verhindern würde.
Die in den obigen Texten angegebenen Werte liegen alle deutlich im sauren Bereich, bei 4, 5 oder so (Ausreißer bis 6)
Jetzt habe ich mich gefragt, welche Bäume denn überhaupt alkalische Rinde haben und eine kleine (engl.) Auflistung gefunden (ohne konkrete Werte), ziemlich verallgemeinernd, hier nur als grober Überblick gedacht.
https://thedailygardener.org/bark-and-ph/
Each tree's bark will have its own pH, and some are more acidic than others.
Larches and Pines are notoriously acidic; Birch, Hawthorne and Oak are acidic too, but slightly less so. Rowan, Alder, Beech, Linden, and Ash are little less acidic again, and Willow, Holly and Elm are getting closer to neutral. Sycamore, Walnut, and Elder are alkaline. The less acidic the bark is, the more growth you are likely to see from colonizing plants and lichens. Pine bark is often bare, whereas Sycamore might have a glorious guest hanging off its bark.