Epiphytic lichen communities on trunks of Pinus sylvestris and Picea abieswere studied on a west–to–east gradient through the central pan of Finland with special reference to macrolichens. Comparisons were made between the two conifer species, the coast of the Gulf of Bothnia and the more continental inland area, open commercial and denser natural forests differing in their local climate, and tree bases (0·0–0·7m) and upper trunks (0·7–2·0m). Differences were found not in species composition but in relative species abundance, the main distinction being between the two tree species. There were also noticeable geographical, vertical and habitatdependent differences. In addition to climatic factors, the importance of bark properties for the epiphytes is briefly discussed.
The objective of the current study is to compare the short‐term accumulation capacity of two epiphytic lichens characterized by a different type of thallus. The lichens Hypogymnia physodes (L.) Nyl. and Usnea hirta (L.) Weber em. Mot. were transplanted either to the vicinity of streets of low volume and slow traffic or to the vicinity of a highway in the city of Oulu, N. Finland, for a period of 45 d. Eleven elements were analyzed before and after transplantation. The two lichen species were found to possess a similar accumulating capacity for K and Mn. Hypogynmia physodes manifests a higher accumumulating capacity than U. hirta for Na, Fe, and Cu, whereas the more sensitive lichen U. hirta exhibits a higher accumulating capacity for Mg, despite a higher primary concentration of these elements in the thallus of H. physodes. Our findings show a relative high concentration of K, Fe, Mg, Zn, Mn, Pb, and Cu in thalli of H. physodes and Mg, Zn, Pb, Cu, and Cd in U. hirta in material transplanted to streets of low volume and slow traffic, over and above the concentration found in thalli retrieved from the vicinity of the highway. This may be explained by the higher rate of abrasion of car engines running idle near traffic lights and by the lesser ventilation near the close‐clustered streets of the inner city.
Podetia of the terricolous lichen Cladina stellaris (Opiz) Brodo, collected in an unpolluted rural area in N. Finland, were wetted with either H # O, diluted acidic solutions of H # SO % , HNO $ and NaHSO $ , simulating acidic rain, or the following salts :The samples were further exposed to combined treatments in both acidic solutions, simulating acidic rain, and heavy metal salts in solution. Lichen samples wetted with H # O at pH 6n8, diluted solutions of H # SO % , HNO $ or a mixture of these two acids produced low concentrations of endogenous ethylene. The application of NaHSO $ greatly increased the production of ethylene. The application of KCl induced a higher rate of ethylene production than the application of K # SO % solutions. The application of Cu-containing solutions enhanced the production of ethylene. The influence of Zn was smaller than that of Cu. Iron was the most effective heavy metal to promote the production of ethylene : very high ethylene concentrations were detected upon the application of FeCl # . Combined treatments in H # SO % or H # SO % jHNO $ followed by either FeCl # or FeSO % , yielded higher concentrations of ethylene than the same treatments in a reversed order. The role of Fe ions in the production of ethylene is discussed in reference to previous works dealing with ethylene production in higher plants, fungi and algae.
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