Bryoflora of the Czech Republic
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Bryophytes are an intrinsic part of various vegetation types in Central European landscapes. The Czech bryoflora is made up of 866 species (207 liverworts, 655 mosses and 4 hornworts) of which 59 are considered to be extinct or have vanished. The great majority are native species, while only four species are of demonstrably alien origin. Two of the alien mosses are invasive and about ten native species or species earlier reported from neighbouring countries are regarded as expanding. The majority of Czech bryophytes belong to temperate montane elements, with a significant proportion of boreal and suboceanic taxa. Arctic-alpine and boreal taxa are at the highest risk of extinction as they are confined to relict habitats. Probably no species of bryophyte is endemic to the Czech Republic. As in the other industrial countries with intensive agriculture and forestry, a significant proportion of the bryoflora is at risk; nearly a third of the species in this country are evaluated as threatened according to IUCN criteria.
Bryophytes typically occur in most Central European vegetation types as a minor but intrinsic component of an ecosystem, except in Sphagnum peatbogs, in which they dominate. Despite their low biomass, the species diversity of bryophytes in the Czech Republic is surprisingly high. The last census of bryophytes (Kučera et al. 2012) credibly recorded a total of 863 species in the Czech Republic, including 207 liverworts, 652 mosses and 4 hornworts, plus 5 subspecies and 23 generally recognized varieties. Since then, one other species has been recorded and two species added as a result of taxonomic revisions. The exact numbers are, however, significantly affected by the taxonomic concepts adopted and level of acceptance of earlier records unsupported by herbarium specimens. Moreover, a large number of the reported taxa is believed to be regionally extinct or has been missing for many decades (38 species were, at the end of 2016, considered extinct and 21 missing for more than 30 years). Still, the number of extant bryophytes in the Czech Republic exceeds 800 species.
4.2 Species Composition and Diversity of Bryophytes in the Czech Republic
The liverworts are assigned to 76 genera, the mosses to 194 and the hornworts to 3 genera (Kučera et al. 2012). However, the generic treatments are experiencing a period of turmoil because of the ongoing molecular-phylogenetic revisions. For instance, the recently published World Checklist of Hornworts and Liverworts (Söderström et al. 2016) accepts four additional genera not recognized by Kučera et al. (2012) and merges two of the recognized genera with others. For the mosses, a comparable recent synopsis is absent, which makes the generic assignments more difficult. Even less stable is the situation in family treatments. For instance, while the largest liverwort families of the last pre-molecular Czech checklist (Váňa 1997) were Lophoziaceae (36 species), followed by Scapaniaceae (25), according to the current checklist (Söderström et al. 2016) these are Scapaniaceae (29 species), followed by Anastrophyllaceae (17), while the Lophoziaceae now have only 11 species. In mosses, the three richest families in the pre-molecular treatment were Pottiaceae (82), followed by Bryaceae (61), Dicranaceae (58) and Grimmiaceae (52). Currently, based on various recent treatments, the largest family is still Pottiaceae (88), followed by Grimmiaceae (55) and Brachytheciaceae (40), while the number of species in Bryaceae has decreased to 38 and in Dicranaceae to 18. The largest genera are still Sphagnum and Bryum (each with 34 currently recognized species), although in the latter genus, narrower concepts are becoming increasingly popular.
The number of species of bryophytes recorded in the Czech Republic reflects multiple factors, the most significant being the area, ecosystem diversity and the level of bryofloristic exploration. Therefore the comparison of species numbers with neighbouring countries is difficult. For example, the number of species of bryophytes recorded in Germany (ca 1150, www.moose-deutschland.de) significantly exceeds that in the Czech Republic mainly because of this country’s larger area (357,168 km2 as compared to 78,866 km2) and greater diversity of habitats. In the neighbouring Poland, also much larger than the Czech Republic (312,679 km2), only approximately 910 species of bryophytes are recorded, i.e. nearly the same number as in the Czech Republic despite the narrower species concepts commonly used by Polish authors (Ochyra et al. 2003; Szweykowski 2006). Nevertheless, Poland might be generally less intensively explored compared to Germany and the Czech Republic, as evidenced by the large number of additions to the Polish bryoflora in recent years. On the other hand, the bryoflora of the Austrian federal state of Carinthia (9536 km2) exceeds that in the Czech Republic (893 species, Köckinger et al. 2008), while there are only 659 species of bryophytes in the somewhat larger Hungary (93,030 km2) (Papp et al. 2010). The latter number, nevertheless, is a consequence of not only the smaller diversity of ecosystems but also the historically lower intensity of floristic research on bryophytes.
The vast majority of the taxa occurring in the Czech Republic are native. Alien bryophytes are generally extremely rare; the only two naturalized alien species (Campylopus introflexus and Orthodontium lineare) are generally regarded as invasive in Central Europe (Essl and Lambdon 2009) and two species (the liverwort Lunularia cruciata and the moss Didymodon umbrosus) are considered to be casual aliens. About ten other species native to the Czech Republic or neighbouring countries are regarded as spreading, with a few additional uncertain cases (Kučera et al. 2012). This situation strongly contrasts with the Czech vascular flora, in which about 1300 out of more than 3550 species are considered naturalized or casual aliens (Danihelka et al. 2012). Low numbers of alien bryophyte taxa are probably most attributable to virtually no deliberate introductions as a consequence of their low horticultural attractiveness, although ephemeral escapes of tropical and subtropical species from greenhouses are rarely recorded even in the Czech Republic. Among the spreading species, most numerous are the epiphytes, some of them with still only a rare occurrence, mostly in north-western Bohemia (Orthotrichum pulchellum and O. rogeri), some of them however are already widespread (Dicranoweisia cirrata and Dicranum tauricum). The spread of Dicranum tauricum has been mapped in detail by Stebel et al. (2012).
A significant percentage of the Czech bryoflora is thought to be threatened. The level of threat has been assessed using IUCN criteria since 1993 and the last evaluation (Kučera et al. 2012) listed 32.6% of the evaluated taxa as threatened or extinct. An additional 13.5% of the taxa qualified for Near Threatened and Data Deficient categories, which left only 54% of the taxa categorized as of Least Concern. The level of threat posed to the Czech bryoflora appears to be similar to the situation in most Central European countries, such as Switzerland (37.0% threatened, 1.4% extinct; Schnyder et al. 2004), Slovakia (34.2% threatened, 2.9% extinct; Kubinská et al. 2001) and Hungary (26.3% threatened, 0.5% extinct; Papp et al. 2010), and the differences are in the reported percentage of Data Deficient taxa (e.g., 6.1% in the Czech Republic compared to 21.1% in Hungary), which might reflect the different ways of evaluating taxa in different countries. Notable representatives of strongly endangered bryophytes are the species occurring in lowland rich fens (Bryum longisetum, Drepanocladus lycopodioides, Meesia longiseta and M. uliginosa; all of them probably went extinct in the Czech fens). These fens started to be converted to agricultural land before the first bryologists of the early nineteenth century could report the occurrence of boreal fen species. Perhaps less pronounced in comparison to lichens are the negative changes in the epiphytic flora. Still epiphytes nearly completely disappeared in northern Bohemia as a consequence of industrial pollution, which peaked in the early 1980s. However, the epiphytic bryoflora, in particular in the Krušné hory Mts, has experienced a remarkable recovery, which to-date has only been intensively studied on the Saxon side of this mountain range (cf. Seifert 2004). This re-establishment of bryophytes has also occurred on the Czech side, although it is less well documented because fewer surveys of epiphytes have been carried out there. Only four epiphytic mosses (Neckera pumila, Nyholmiella gymnostoma, Paraleucobryum sauteri and Ulota drummondii) are regarded extinct in the Czech Republic.
4.4 Phytogeographic Aspects
The dispersal capacity of spore-producing bryophytes is generally considerably greater than that of seed plants. Consequently, small distribution ranges are rare or at least do not exist for a long time in bryophytes. There are very few examples of convincingly stenoendemic species of bryophytes in Europe and except for one uncertain case none is presently considered to occur only in the Czech Republic. Several dozens of widely distributed species were originally described from the Czech Republic, including Racomitrium sudeticum (Fig. 4.2c), described from the Krkonoše Mts, and Fossombronia wondraczekii and Hilpertia velenovskyi (Fig. 4.2d), described from localities in Prague. The same applies to Bryum moravicum, described by Podpěra as a southern-Moravian endemic, which was recently shown to be the oldest name for a widely distributed species (Kučera and Holyoak 2005). Even very recently, three taxa were described from localities restricted to the Czech Republic: Platyhypnidium grolleanum, which is probably only a rheophytic modification of the widespread Rhynchostegium riparioides, and two Orthotrichum taxa, O. moravicum (Fig. 4.2e) and O. affine var. bohemicum. Orthotrichum moravicum was recently recorded from Slovakia and Tajikistan (Plášek and Číhal 2012) and O. affine var. bohemicum from Slovakia, Poland, Ukraine, Belgium and the USA (Plášek et al. 2016). An interesting example of a putatively stenoendemic species described from the Czech Republic and not so far recorded from outside Central Europe, is the hornwort Anthoceros neesii (Fig. 4.2f). Although it occurs in the common and widely distributed habitat of stubble fields in submontane regions on non-calcareous substrates, it seems to be surprisingly rare and was long regarded as having vanished from the Czech Republic.
4.5 Bryophytes in Vegetation
The composition of the bryoflora reflects both general macroclimatic conditions, which affect the local species pool, and specific site conditions, determined by the substrate and geomorphology. In contrast to the vascular plant flora, the role of the micro-relief and substrate conditions is generally much greater for bryophytes as a consequence of both their smaller size and greater sensitivity to environmental conditions in the absence of barriers to evaporation from the surface of moss gametophytes. This might result in vastly different bryofloras occurring in one type of vegetation under similar climatic conditions. The following paragraphs briefly mention the bryofloristically conspicuous features of the major natural vegetation types occurring in four zonal and extrazonal biomes in the Czech Republic (see Fig. 7.1 in Chap. 7, this book).
Mesic broad-leaved forests in the broad-leaved deciduous forest biome may be both relatively poor in bryophytes, as in oak-hornbeam or beech forests without rock outcrops, and rich, as in moist (sub)montane beech and beech-fir forests on rugged topography. The bryoflora composition is also significantly affected by management. Rapid turnover of trees and removal of coarse woody debris has an adverse effect on epiphytic and epixylic bryoflora, whereas old-growth forests, such as the famous Žofínský prales in southern Bohemia, are important biodiversity hot-spots (Kučera 2009; Táborská et al. 2015; an example of a rare epiphytic moss is Anacamptodon splachnoides; Fig. 4.3b). As in the case of the thermophilous forests, locally richest or bryofloristically most interesting sites in the landscapes with mesic broad-leaved forests are often the rocky habitats. The most interesting examples are the boulder screes in the České středohoří Mts in northern Bohemia, with many prominent glacial relicts such as the liverworts Gymnomitrion corallioides and Sphenolobus saxicola (Němcová 2000), or the sandstone pseudokarst areas in northern Bohemia, also with a large numbers of relict species (e.g. Dicranum elongatum and Hygrobiella laxifolia). Another bryologically important type of azonal vegetation in the deciduous forest biome is the local occurrence of fens and bogs. The best preserved rich fens with the bryologically most interesting flora are in the Doksy area in northern Bohemia, the Bohemian-Moravian Highlands and the Třeboň Basin in southern Bohemia.
Montane coniferous forests (the spruce taiga), despite long-lasting human management, are home to a significant number of bryophytes often occurring abundantly on the floor of forests even in the absence of diversified micro-relief. This is particularly the case in water-logged forests and forest on boulder screes in topographic situations with a high air humidity. Large pleurocarpous mosses (Eurhynchium angustirete, Hylocomium splendens and Thuidium tamariscinum) together with similarly robust species of Dicranum, often dominate the forest floor and prevent smaller species from establishing. This results in a relatively low species diversity except in topographically heterogeneous areas. Spruce forests richest in bryophyte species are typically those occurring in lower parts of glacial cirques in the Krkonoše, Hrubý Jeseník and Šumava Mts. The glacial cirques are possibly the bryologically richest sites in the Czech Republic, because of the extremely diversified microsite conditions, substrate types and high humidity (Kučera et al. 2004). Lowland pine taiga, which occurs locally on sandy substrates, also mostly has a well-developed moss layer, dominated typically by large species of Dicranum (D. polysetum, D. scoparium, D. spurium; Fig. 4.3c), Leucobryum and Campylopus (notably C. flexuosus). Bryologically important in the coniferous forest biome (both in the montane and lowland types) is also the local occurrence of acidic bogs, dominated by species of Sphagnum, which constitute the major part of their biomass.
Subalpine tundra is generally poor in bryophyte species. This particularly applies to the subalpine grasslands dominated by Nardus stricta, where niches for mosses only occur locally on elevated landforms. On the other hand, rock outcrops and screes are a refuge for arctic-alpine relict species such as the liverwort genera Gymnomitrion, Marsupella and Tetralophozia, and moss species Andreaea rothii, A. frigida (Fig. 4.3d) and Grimmia elongata. They are strongly endangered by successional changes, as the altitudinal and spatial extent of the tundra biome in the Czech Republic is extremely limited. The reasons underlying these changes are multiple; Treml et al. (2016) recently argued for the major importance of the absence of cattle grazing for the advance of the treeline, in addition to the increasing temperatures over the last century (Migała et al. 2016).
I am grateful to Štěpán Koval and Vítězslav Plášek for providing photographs, Milan Chytrý and Zdeněk Kaplan for helpful comments on earlier versions of the text and Tony Dixon for the English proofreading.
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