8. Mosses, liverworts and lichens in forests

Wiesław Fałtynowicz

Photo 4. Leucorbryum glaucum - common forest moss - Radziwiłów Forest District - by Jerzy Wawrzoniak

The numerous moss species feature a narrow ecological amplitude range and therefore they show high sensitivity to environmental changes, both natural and anthropogenic. Therefore, they are good bioindicators and in this respect they give way only to lichens. They are used for monitoring atmospheric air pollution, water purity, microclimatic changes or for analysing environmental gradients. They are also used as indicators of stands' ecological properties. [25].

 Liverworts are in most cases stenotopic organisms and respond swiftly to even slight changes taking place in stand conditions. Therefore, they can be good bioindicators of environmental changes. The rarity of occurrence of numerous taxons and their small size, making it difficult to find them and correctly identify their species, are the obstacles to their common use [10]. 

Lichens are a specialized group of fungi which derive from the combination of two organisms: heterotrophic fungus and homotrophic algae [7]. The reaction of lichens to natural and anthropogenic factors is fast and clear. Visually, it is reflected in morphological transformations of thalluses, easy to identify and interpret, and in quantitative changes. Sometimes it leads to abandoning of the transformed areas. [4, 5]. Therefore, lichens belong to the organisms strongly endangered throughout Europe.  "The Polish Red Data Book of Lichens that are Endangered and Threatened by Extinction" includes nearly 40% of species known in Poland, of which extinct lichens and those threatened by extinction account for 15% [2]. Continuous observations of the direction and rate of quantitative and qualitative changes in the Populations of individual lichen species provide important information about the ecology of these organisms. However, in the first place they supply data on natural and anthropogenic changes taking place in stand conditions, including the degree of atmospheric air contamination. For this reason, lichens are commonly used all over the world as bioindicators of environmental changes.

In Poland, in addition to forest monitoring, lichens are used as bioindicators also in the Integrated Environmental Protection Monitoring [24]. They are also an element of the biological monitoring program. [3].

Mosses are represented on the second-level level POPs in great abundance with regard to both, the number of species and area occupancy. In 2003, 64 species were found, half of which occurred sporadically on no more than 3 POPs, while the remaining 33% did not exceed the first degree of permanence - Table 8. Only 10 species occurred with at least second degree of permanence, and on half of all POPs only Pleurozium schreberi was found. This coniferous-forest acidophilus moss also occurred in the highest abundance in all natural-forest regions, with the exception of Carpathian and Sudeten regions. Its mean area coverage in phytosociological surveys exceeded 20%. In the Małopolska natural-forest region, it reached nearly 40% - Table 9. Distribution of Hypnum cupressiforme is specific.

This subatlantic species occurred most frequently only in western Poland, in particular where suboceanic influences are the strongest (Silesian, Baltic and Sudeten natural-forest regions) - Table 9.

Due to the fact that the majority of POPs are located in pine or spruce stands, the most frequent and most abundant were mosses representating communities with predominant coniferous species: Pleurozium schreberi and Dicranum polysetum, common forest species such as: Hypnum cupressiforme, Dicranum scoparium and Polytrichum formosum and ubiquitic species: Pohlia nutans and Dicranella heteromalla.

Average coverage by spore-producing species (mainly by mosses) on POPs in the majority of natural-forest regions oscillated between 39% and 50% only in the mountains.

In the majority of natural-forest regions, the mean coverage of POPs with the spore-producing plant layer (this layer is composed mainly of mosses) ranged from 39% to 50%. Only in the mountains (Carpathian and Sudeten regions) it was significantly lower and did not exceed 10% - Table 10. The coverage of the spore-producing plant layer is distinctly higher under under coniferous sands than broadleaved stands.

Fourteen moss species found on POPs are subjected to partial protection. These are:

Aulacomnium palustre                                     Climacium dendroides

Hylocomium splendens                                    Leucobrum glaucum 

Pleurozium schreberi                                       Polytrichum commune

Pseudoscleropodium purum                Ptilium crista-castrensis

Rhitidiadelphus squarrosus                              Rhitidiadelphus triquetrus

Sphagnum fallax                                              Sphagnum palustre

Sphagnum recurvum                            Thuidium tamariscinum

Moreover, Dicranum polysetum is listed in the "Red Data Book of Endangered Moss Species in Poland" [15] under category VU (vulnerable).

By nature, liverworts occur in plant communities in small numbers and, moreover, owing to their small dimensions, they are difficult to notice. In 2003, 12 species of these plants were found on POPs - Table 11. The most popular species was Ptilidium ciliare, which, at the same time, was a relatively big, and one of the most easily spottable liverworts. This is a subatlantic species, quite frequently occurring in the phytocenoses of pine forests, particularly in the western part of the country. Bazzania trilobata characteristic for mountain coniferous forests deserves attention. It also occurs in greater numbers in northern-eastern Poland. In the remaining area, its occurrence is exceptionally rare.

In 2003, 46 taxons of lichens were found on all second-level level POPs - Table 12. Only two epiphytic species common throughout Europe Hypogymnia physodes and Lecanora conizaeoides occurred in higher abundances and were registered on about half of POPs. Other taxons were collected very rarely. Most of them were sporadic (3 and less occurrences). Apart from the above-mentioned species, only Scoliciosporum chlorococcum was found on over 10% of POPs. This species certainly occurs more frequently, however owing to its inconspicuous thallus looking like a dusty residue and almost invisible fruiting bodies, it is generally passed over unnoticed. Also the genus Lepraria is certainly underrepresented. The vast and up-to-date knowledge of the ecology and distribution of this type of lichens in Poland, based on a monograph by M. Kukwa [12], provides that the greenish or greyish powder-like thalluses of lichens could be easily passed over unnoticed while collecting materials.

Six lichen species found on POPs are subjected to legal protection. These are: Cetraria islandica, Cladonia arbuscula, C. ciliata, C. rangiferina, Evernia prunastri and Parmeliopsis ambigua.

Among lichen species found on POPs, six are included in the "Red Data Book of Endangered Lichen Species in Poland" [2]. These are:

Cetraria islandica (VU - vulnerable)

Cladonia rei (DD - lack of sufficient data)

Evernia prunastri (LR - at low risk)

Porpidia cinereoatra (VU)

Porpidia glaucophaea (VU)

Trapelia placodioides (LR)

In Poland nearly all aforementioned protected species and those specified in the "Red Data Book" are commonly occuring and the level of threat to them- insignificant.

Average coverage by epiphytes (almost solely by lichens) on the stumps of monitored tress in the natural-forest regions is relatively high and ranges from 31% (Wielkopolska-Pomerania) to nearly 60% (Mazury-Podlasie) - Table 10.

In 2003, less species of mosses (64), liverworts (12) and lichens (46) were found on the second-level level POPs than five years before (78, 18 and 54, respectively). First of all, sporadic species that occurred in 1998 on one to several POPs were not found again. Most of the remaining moss species were found this time on a smaller number of POPs. A detailed analysis of the situation provides sufficient basis to conclude that it results from a less careful collection of materials and, in particular, from passing over decaying wood. Similar conclusions can be drawn with regard to liverworts. Changes in the number of occurrences of lichens, when compared to 1998, also resulted from the same reason, but they were even bigger. In the case of lichens, the most notable decline in the number of occurrences was among Hypocenomyce scalaris (from 44 to 6), Lepraria incana (from 54 to 11) and Cladonia macilenta (from 27 to 7). Also coverage with epiphytes decreased - compare Table 10 and [6].

Coverage values for the spores-producing plant layer were down in comparison with 1998, though the differences were not great.