Abstract
The pH of tree bark is affected by many factors, amongst them epiphytic bryophytes changing in their active state environment. Thus, we hypothesized that bryophytes can change bark acidity, dependently of the inclination of the branches, as inclination affect the water regime and particle deposition. We measured the pH under bryophyte cushions and compared it to nearby naked bark. Additionally, we compared results with experimental bark covering with neutral cover. We found that the pH of naked bark declines with decreasing inclination of trunks. Although bryophyte cover did not generally change the pH of the bark, there was a significant interaction with inclination: with higher inclination, bryophytes decrease the pH reaction of bark, while with lower inclination they increase it. One possible explanation may lie in changes to alkaline particle deposition, or conversely in the acidification of the bark by leaching. In addition, an experiment with a neutral cover showed that naked bark covering would substantially increase pH. As, on average, bryophytes do not change the pH of bark, there can be mutual interference between the alkalizing effect of the bark cover itself and the acidifying biological effect of bryophytes.
Highlights
Tree bark varies in pH [1]
Tree species determines the shape of the leaves, the angle of connection of the branches, the architecture of the bark, and the amount and type of substances leached from the leaf area and the bark [7,8]
Warncke (n = 10), Orthotrichum pallens Brid. (n = 11), Orthotrichum pumilum Sw. (n = 8), Ulota bruchii Hornsch. ex Brid. (n = 11), and Ulota crispa (Hedw.) Brid. (n = 6). Another nine samples were excluded from the analysis because they belonged to species of bryophytes with fewer than 6 samples (Orthotrichum patens Bruch ex Brid., n = 4; Orthotrichum striatum Hedw., n = 2) or were collected from another phorophyte (Sorbus aucuparia L., n = 3)
Summary
Tree bark varies in pH [1]. Bark pH is influenced by several biotic and abiotic factors and is species-specific among woody plants [2,3,4]. Tree species determines the shape of the leaves, the angle of connection of the branches, the architecture of the bark, and the amount and type of substances leached from the leaf area and the bark [7,8]. Another condition that affects pH reaction is the size of the tree (the crown area, the total number of branches), which is closely related to its age and circumference [9,10]. Abiotic factors influencing the pH of the bark are the type of precipitation, seasonality [16,17], the amount and intensity of precipitation [18], the deposition of alkaline dust particles on the tree surface, their aqueous solutions [1,19], and wind [20]
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