Number Of Lichen Species Research Articles

Lichens as indicators of air pollution in a steel producing town in South Wales

The lichen flora of a given region depends upon a multiplicity of factors. Some factors act directly or indirectly upon the lichen thallus; in addition the lichen thallus is capable, to some extent at least, of exerting a modifying influence upon the macro- and micro-environment. The polluted centre of Port Talbot, a steel town, has a restricted number of crustose and rather depauperate species. This ‘lichen desert’ is quite small possibly because either (a) the atmosphere is not heavily polluted, or (b) there is a rapid dilution of pollutants. With distance away from Port Talbot there is an increase in the number of lichen species and a change in the proportion of the various growth forms. Abutting the ‘lichen desert’ is a zone in which Parmelia sulcata, P. saxatilis, Cladonia coniocraea, and C. fimbriata are the most widely represented species. This is followed by a further zone dominated by Usnea comosa, U. florida, Cetraria glauca, and Cladonia impexa in particular. It must be noted that these zones are not clearly defined; there is a gradation in growth forms and a gradual change in the abundance of various species.

Changes in the Lichen Flora Following air Pollution

Kvarntorp, in the province of Narke, is a small industrial town situated about 160 km west of Stockholm and about 260 km northeast of Gothenburg in the southern part of Sweden. It developed in connection with a state-owned shale oil works, which started production in 1942, and closed on the 1.10. 1966. The raw material consisted of alun shale that yielded large quantities of sulphur dioxide during stripping. It was not long before this resulted in damage to vegetation, particularly the coniferous forest. The attention of the National Institute for Plant Protection was drawn to the problem in 1948 and in 19511953 a first lichen investigation was made in the Kvarntorp area (Skye 1958). Several other investigations were carried out by, among others Johansson (1959). Skye stated that areas with a high content of sulphur dioxide in the air contained a lower number of lichen species than normal. By comparing the distribution of certain lichens with the wind-rose he believed he could demonstrate that the elements harmful to lichens were contained in the smoke from the shale oil works. In the summers of 1967 and 1968 Hallberg continued the studies on distribution of the epiphytic lichens within the original investigation areas (Hallberg 1969).

Biochemistry in the taxonomy of lichens.

THE application of biochemical methods to plant taxonomy was first made in the lichens, in 1867, when potassium hydroxide and calcium hypochlorite were found to give characteristic colour reactions when applied to the thallus of certain species. Most present-day lichenologists employ these reactions as an important character in the description of species. In a large number of lichen species the exact constitution of the lichen acids causing colour reactions is known, mainly owing to the researches of Zopf1 and Asahina2,3. The latter has originated a method of microchemical analysis whereby the lichen acids can be determined by the form of the crystals which they produce under the microscope when recrystallized from various, solutions4, this method requiring the extraction of only a small portion of the thallus with acetone.