64 65 3 Mohelno Serpentinite Steppe Pavel Daněk Introduction The Mohelno Serpentinite Steppe (Mohelenská hadcová step) is situated in south-western Moravia near the small town of Mohelno, about 30 km west of Brno, in the low-altitudinal marginal area of the Bohemian-Moravian Highlands. The steppe occupies the south-facing slopes of the Jihlava River Valley which dissects a gently undulating landscape. The upper part of the south-facing slopes of the Mohelno Serpentinite Steppe with a dry grassland of Stipa dasyphylla in the foreground and open Pinus sylvestris woodland in the background. Photo P. Daněk. Geology, soils and climate The area is built of metamorphic rocks (mainly granulite, gneiss and amphibolite) which are locally overlaid by loess. An important feature of this region is the occurrence of serpentinite. This ultrabasic metamorphic rock can also be found in other parts of the Bohemian Massif (e.g. the Slavkovský les Mountains in western Bohemia, the Bohemian Forest foothills in south-western Bohemia and other parts of the Bohemian-Moravian Highlands), though in south-western Moravia, and particularly near Mohelno, the serpentinite effect on vegetation is magnified by the location of its outcrops in a deep river valley. While the gentle slopes allow an accumulation of a soil layer deep enough to suppress the effects of the serpentinite bedrock on vegetation to some extent, the steep slopes of the Jihlava River Valley are being permanently eroded, for which reason the serpentinite bedrock has a stronger influence on the associated flora and fauna. Serpentinite is an ultrabasic rock characterized by a high magnesium content combined with a relatively low calcium content. Serpentinite soils are usually deficient in nutrients (nitrogen, phosphorus and potassium) and contain large amounts of heavy metals (cobalt, nickel and chromium). In addition to the chemical properties of serpentinite, its physical characteristics are also important. Niessl, G. 1868. Über die Flora der Eisleithen bei Frain. Verhandlungen des Naturforschenden Vereines in Brünn 6: 62–68. Oborny, A. 1879. Die Flora des Znaimer Kreises. Verhandlungen des Naturforschenden Vereines in Brünn 17: 105–304. Podborský, V. & Vildomec, V. 1972. Pravěk Znojemska [Prehistory of the Znojmo district]. Musejní spolek v Brně & Jihomoravské muzeum ve Znojmě, Brno. Rydlo, J. 1995. Vodní makrofyta v Národním parku Podyjí [Aquatic macrophytes in the Podyjí National Park]. Muzeum a současnost, Řada přírodovědná 9: 129–148. Sedláková, I. & Chytrý, M. 1999. Regeneration patterns in a Central European dry heathland: effects of burning, sod-cutting and cutting. Plant Ecology 143: 77–87. Táborská, J. 1999. Historický vývoj krajiny východní části Národního parku Podyjí v různých časových horizontech 19. a 20. století [Historical development of the landscape in the eastern part of the Podyjí National Park during the 19th and 20th centuries]. Thayensia 2: 61–73. Tichý, L. 1998. Dlohodobá teplotní měření na lokalitě Sloní hřbet (NP Podyjí) ve vztahu ke struktuře a fenologickým projevům vegetačního krytu [Long-term temperature measurements at the locality of Sloní hřbet, Podyjí National Park, in relation to the structure and phenological development of vegetation]. Thayensia 1: 67–81. Tichý, L. 1999a. Predictive modeling of the potential natural vegetation pattern in the Podyjí National Park, Czech Republic. Folia Geobotanica 34: 243–252. Tichý, L. 1999b. Teplotní poměry a vegetace na lokalitě Sloní hřbet v Národním parku Podyjí [Temperature and vegetation pattern at the Sloní hřbet Ridge, Podyjí National Park]. Preslia 70 (1998): 289–301. Vild, O. & Stejskal, R. 2013. Vliv experimentální pastvy na lesní podrost v Národním parku Podyjí [The impact of experimental grazing on the woodland understory in the Podyjí National Park]. Thayensia 10: 27–38. Vrška, T. 1998. Historický vývoj lesů na území NP Podyjí a v bližším okolí do roku 1948 [Historical development of forests in the Podyjí NP and its close surroundings until the year 1948]. Thayensia 1: 101–124. Zelený, D. & Chytrý, M. 2007. Environmental control of vegetation pattern in deep river valleys of the Bohemian Massif. Preslia 79: 205–222. 3 66 67 The dark colour and low thermal conductivity of the rock lead to its strong heating during the summer when surface temperatures can reach 50 °C, exceeding the air temperature by more than 20 °C (Hrudička 1937). Although some of these properties are also characteristic of other rock types, their unique combination on serpentinites constitutes stress conditions under which only some species can survive. In contrast to the sunny south-facing serpentinite slopes with shallow leptosols which host mainly steppic vegetation and pine forests, the opposite north-facing slopes are mostly formed of granulite and are covered by broad-leaved deciduous forests on cambisols. The climate is relatively warm and dry with mean annual temperatures slightly above 8 °C and the annual precipitation sum of approximately 550 mm. History of botanical research and nature conservation The local botanist Carl Roemer found Mohelno’s most famous plant species, the fern Notholaena marantae, in 1858. In the early 20th century, the flora of the Mohelno serpentinites was studied by Josef Podpěra who drafted the first proposal for the establishment of a nature reserve in 1914. In the 1920s, his work was continued by Jindřich Suza who studied the relationship between bedrock and vegetation and gave a detailed description of local plant communities (Suza 1928). In 1933, a nature reserve was finally established on an area of 50 ha to prevent the steppe from being destroyed by stone mining. Intensive research continued in the reserve, resulting in a series of seven edited volumes published between 1934 and 1948 presenting knowledge in several fields (geology, soil science, climatology, botany and zoology; Veselý 2002). The nature reserve was re-established in 1952. Its previously ambiguous borders were newly delineated and the steppe was no longer allowed to be used as pasture. Sheep and goat grazing had been a traditional form of management and its abandonment led to successional changes of steppic vegetation towards pine forests. While only 13% of the reserve’s area was covered by forests in 1950, this proportion had increased to 62% by the late 1980s (Čechová et al. 1997). Following expert discussion, a decision was taken to cut much of the overabundant pine as well as some alien tree species (Robinia pseudoacacia and Pinus banksiana). The main phase of the reduction of tree stands took about ten years and was followed by the restoration of sheep and goat grazing in 1997. This traditional form of management has been practiced ever since (Čech 2005). Construction of the nearby Dukovany Nuclear Power Station and associated Dalešice and Mohelno dams had a significant impact on the local landscape and led to flooding of a 30-km-long section of the Jihlava Valley in 1978. The Mohelno dam, which serves as a reservoir of process water for the nuclear power plant, borders the western part of the Mohelno Serpentinite Steppe. The large amount of water contained in the reservoir affects the mesoclimate of the valley by lowering daily temperature amplitudes and increasing air humidity (Quitt 1996) which might affect vegetation, particularly in the lower parts of the slopes. Intensive research into the steppe and its surroundings resulted in several botanical studies in the 1990s. Chytrý & Vicherek (1996) described the natural and semi-natural vegetation of the Oslava, Jihlava and Rokytná River Valleys including the unique plant communities of the Mohelno Serpentinite Steppe and other serpentinite outcrops in the Jihlava Valley. Unar (1996) produced a flora inventory of the Mohelno Steppe and Koblížek et al. (1998) characterized the flora of selected localities in the region. The area of the reserve was extended to approximately 110 ha in 2012. Vegetation and flora There are several phytogeographically distinct species growing on the steppe. The aforementioned Notholaena marantae, a southern European fern, reaches its northern distribution limit here at an isolated site. Stipa dasyphylla is a continental Eurasian grass also known from some other southern Moravian localities, but all these occurrences are isolated from the species’ continuous distribution range. Scorzonera austriaca, a species from the Asteraceae family, reaches its north-western distribution limit here. The upper part of the steppe and the adjacent plateau are covered by dry grasslands (alliance Festucion valesiacae) dominated mainly by narrow-leaved tussocky fescues (Festuca rupicola, F. valesiaca) and feather grasses (Stipa capillata, S. dasyphylla, S. pulcherrima) accompanied by other drought-adapted species (Carex humilis, Dorycnium germanicum, Dianthus carthusianorum agg., The Mohelno Serpentinite Steppe with a meander of the Jihlava River in the 1920s and in 2014. The forest has expanded considerably due to the abandonment of grazing. Photo archive of the Department of Botany and Zoology, Masaryk University, and J. Chytrý. 3 68 69 The Mohelno Serpentinite Steppe in the Jihlava River Valley south of the town of Mohelno. Acidophilous dry grassland in the Kozének Nature Reserve. Photo D. Zelený. Seseli hippomarathrum, Thymus praecox and Veronica spicata). The plateau between the river valley and the town of Mohelno is grazed by sheep. Patches of specific grassland vegetation type dominated by Festuca pulchra with the occurrence of the serpentinite specialist Armeria elongata subsp. serpentini can be found here. Plants tend to grow much smaller than usual in this part of the steppe, and much attention has been paid to this phenomenon in the past. Rudolf Dvořák described 279 of these ‘nanisms’ in 170 plant species and attributed them to the low availability of nutrients and water on serpentinite soils (Dvořák 1935). However, since the abandonment of pasture these ecomorphoses have largely disappeared and it is currently believed that they were mainly caused by grazing (Kolář & Vít 2008). The lower slopes are steep with numerous gullies and serpentinite outcrops. In this part of the reserve, the vegetation of dry grasslands changes to rocky steppes (alliance Alysso-Festucion pallentis) with dominant Festuca pallens and an admixture of other plants capable of growing on shallow stony soils (Allium flavum, Alyssum montanum, Euphorbia seguieriana, Linaria genistifolia, Melica ciliata, Pilosella echioides and Seseli osseum). In late summer, this vegetation is dominated in places by the grass Bothriochloa ischaemum. The serpentinite rock outcrops are a habitat of Notholaena marantae which grows together with another fern, the serpentinite specialist Asplenium cuneifolium (Vicherek 1970). Along with other species confined to rock crevices (A. ruta-muraria, A. trichomanes, Sedum album) they form the association Notholaeno marantae-Sempervivetum hirti (alliance Asplenion cuneifolii) which can only be found here and on a few serpentinite sites in Austria. Scattered individuals of Scots pine (Pinus sylvestris) are common all over the steppe, while some shrubs (Berberis vulgaris, Prunus mahaleb) form patches of dense scrub. The eastern part of the reserve is covered by forests. Most of them consist of Pinus sylvestris which expanded here after the abandonment of pasture, so the herb layer composition is similar to that of the steppe, though usually less diverse. The potential natural vegetation here is supposed to be a deciduous oak forest dominated by Quercus petraea with pine restricted mainly to rock outcrops. These oak forests on serpentinite can still be found elsewhere in the Jihlava Valley and were described as an endemic association Asplenio cuneifolii-Quercetum petraeae (Chytrý & Horák 1997), a specific type related to the broad association Sorbo torminalis-Quercetum (alliance Quercion petraeae). In some places with deeper soils (mostly close to the valley bottom), stands with an admixture or dominance of broad-leaved species (Acer campestre, Carpinus betulus, Quercus petraea, Tilia cordata) occur and these forests can be classified as oak-hornbeam forests (association Galio sylvatici-Carpinetum betuli, alliance Carpinion betuli) if their understorey contains mesophilous forest species (e.g. Actaea spicata, Asarum europaeum, Campanula persicifolia, Galium odoratum, Hepatica nobilis, Pulmonaria officinalis agg.). On the valley floor, close to the river, remnants of floodplain forests of the association Stellario nemorum-Alnetum glutinosae (alliance Alnion incanae) can be found. These forests are rich in vernal species that flower before tree-leaf flushing (e.g. Adoxa moschatellina, Corydalis solida, Ficaria verna and Gagea lutea). The riverbanks are lined with discontinuous vegetation dominated by the grass Phalaris arundinacea accompanied by other hygrophilous species such as Carex buekii and Scrophularia umbrosa (alliance Phalaridion arundinaceae). Kozének Nature Reserve Located about 4 km east of the town of Mohelno, the Kozének Nature Reserve provides ecological contrasts to the serpentinite steppe. Its gentle slopes on granulite and gneiss are occupied mainly by dry acidophilous grasslands of the alliance Koelerio-Phleion phleoidis. This vegetation is dominated by grasses (e.g. Festuca ovina, F. rupicola, Helictochloa pratensis and Phleum phleoides) and hosts several endangered species (e.g. Orchis morio, Pulsatilla grandis and Saxifraga bulbifera). In some places thermophilous species are less abundant and the grasslands have different dominants (e.g. Briza media, Carex pallescens, Danthonia decumbens and Nardus stricta) characteristic of the nutrient-poor acidophilous Nardus grasslands of the alliance Violion caninae. These grasslands were historically used as pasture, similarly to the Mohelno Steppe, evidence of which is provided by scattered old individuals of shrubby juniper (Juniperus communis). The outer parts of the reserve are covered by hay meadows of the alliance Arrhenatherion elatioris dominated by grasses (Agrostis capillaris, Anthoxanthum odoratum, Arrhenatherum elatius, Festuca rubra) and including several mesophilous herb species (e.g. Centaurea jacea, Ranunculus acris and Rhinanthus minor). 3 70 71 Appendix 3 Selected species of vascular plants of the Mohelno Serpentinite Steppe. Species of dry grasslands and rock outcrops Achillea collina Acinos arvensis Agrimonia eupatoria Agrostis capillaris Agrostis vinealis Ajuga genevensis Allium flavum Alyssum alyssoides Alyssum montanum Anchusa officinalis Antennaria dioica Anthericum ramosum Anthoxanthum odoratum Anthyllis vulneraria Arabidopsis thaliana Arabis hirsuta Arenaria serpyllifolia agg. Armeria elongata subsp. serpentini Arrhenatherum elatius Artemisia campestris Artemisia vulgaris Asperula cynanchica Asplenium cuneifolium Asplenium ruta-muraria Asplenium trichomanes Aster amellus Astragalus glycyphyllos Atriplex patula Ballota nigra Berberis vulgaris Berteroa incana Biscutella laevigata subsp. varia Bothriochloa ischaemum Brachypodium pinnatum Briza media Bromus erectus Bromus hordeaceus Bromus japonicus Bupleurum falcatum Calamagrostis epigejos Calluna vulgaris Campanula patula Campanula rotundifolia agg. Capsella bursa-pastoris Carduus acanthoides Carduus nutans Carex caryophyllea Carex humilis Carex michelii Carex muricata Carex praecox Carlina acaulis Carlina vulgaris Carum carvi Caucalis platycarpos Centaurea jacea Centaurea scabiosa Centaurea stoebe Centaurea triumfetti Cerastium arvense Cerastium holosteoides Cerastium pumilum Chamaecytisus ratisbonensis Chenopodium album Chondrilla juncea Cichorium intybus Cirsium arvense Cirsium vulgare Clinopodium vulgare Convolvulus arvensis Conyza canadensis (neo) Cotoneaster integerrimus Cuscuta epithymum Cynodon dactylon Cynoglossum officinale Cystopteris fragilis Cytisus nigricans Dactylis glomerata Danthonia decumbens Descurainia sophia Dianthus carthusianorum agg. Dorycnium germanicum Echium vulgare Elymus hispidus Erigeron acris Erophila verna Eryngium campestre Euphorbia cyparissias Euphorbia epithymoides Euphorbia seguieriana Falcaria vulgaris Festuca ovina Festuca pallens Festuca pulchra Festuca rubra Festuca rupicola Festuca valesiaca Filago arvensis Filipendula vulgaris Fragaria viridis Frangula alnus Gagea bohemica Gagea lutea Galatella linosyris Galeopsis angustifolia Galium album Galium verum Genista pilosa Genista tinctoria Geranium pusillum Hackelia deflexa Helianthemum grandiflorum subsp. obscurum Helictochloa pratensis Herniaria glabra Hieracium schmidtii Holosteum umbellatum Hylotelephium maximum Hypericum perforatum Inula conyzae Juniperus communis Knautia arvensis Koeleria macrantha Koeleria pyramidata Lactuca serriola Leontodon hispidus Lepidium campestre Leucanthemum vulgare Ligustrum vulgare Linaria genistifolia Lotus corniculatus Luzula campestris Medicago falcata Melica ciliata Melica transsilvanica Melilotus officinalis Muscari comosum Myosotis arvensis Myosotis ramosissima Myosotis stricta Noccaea caerulescens Nonea pulla Notholaena marantae Odontites vernus subsp. serotinus Oenothera moravica (neo) Opuntia phaeacantha (neo) Orchis morio Origanum vulgare Orobanche alba Orobanche coerulescens Phelipanche arenaria Phelipanche purpurea Phleum phleoides Picris hieracioides Pilosella echioides Pilosella officinarum Pimpinella saxifraga Pinus sylvestris Plantago lanceolata Plantago media Poa bulbosa Polypodium vulgare Potentilla argentea Potentilla heptaphylla Potentilla incana Prunella grandiflora Prunus fruticosa Prunus mahaleb Prunus spinosa Quercus petraea Quercus robur Ranunculus acris Ranunculus bulbosus Robinia pseudoacacia (neo) Plate 3 Plants of the Mohelno Serpentinite Steppe: (a) Pinus sylvestris, (b) Seseli hippomarathrum, (c) Notholaena marantae, (d) Euphorbia seguieriana, (e) Berberis vulgaris, (f) Senecio erucifolius, (g) Scabiosa canescens, (h) Stipa capillata, (i) Asplenium cuneifolium, (j) Prunus mahaleb, (k) Bothriochloa ischaemum, (l) Thymus praecox. 3 72 73 Veronica officinalis Vicia pisiformis Vincetoxicum hirundinaria Viola collina Viola odorata Viola reichenbachiana Viola riviniana Viscaria vulgaris Viscum album subsp. austriacum Dry grassland with Carex humilis and Dorycnium germanicum in the canopy openings of a pine woodland in the Mohelno Serpentinite Steppe. Photo P. Daněk. References Čech, L. 2005. Ochranářská péče o NPR Mohelenská hadcová step v uplynulých 20 letech [Conservation management in the Mohelenská hadcová step National Nature Reserve over the past 20 years]. In: Aktuální otázky ochrany a výzkumu NPR Mohelenská hadcová step – II, pp. 22–23. MZLU v Brně, Brno. Čechová, J., Jelínková, J. & Unar, J. 1997. Vývoj vegetace Národní přírodní rezervace Mohelenská hadcová step v závislosti na řízení ochrany území a na prováděných bioregulačních zásazích [Vegetation development in the Mohelenská hadcová step National Nature Reserve depending on the conservation management of the area and the bioregulation measures]. Přírodovědný sborník Západomoravského muzea v Třebíči 27: 1–51. Chytrý, M. & Horák, J. 1997. Plant communities of the thermophilous oak forests in Moravia. Preslia 68 (1996): 193–240. Chytrý, M. & Vicherek, J. 1996. Přirozená a polopřirozená vegetace údolí řek Oslavy, Jihlavy a Rokytné [Natural and semi-natural vegetation of the Oslava, Jihlava and Rokytná River Valleys]. Přírodovědný sborník Západomoravského muzea v Třebíči 22: 1–125. Dvořák, R. 1935. Nanismy (trpasličí formy rostlinné) [Nanisms (dwarf plant forms)]. Mohelno 5a: 1–152. Hrudička, B. 1937. Klimatografie jihozápadní Moravy se zřetelem k poměrům refugia mohelenského [Climatography of south-western Moravia with reference to the Mohelno refugium]. Mohelno 1a: 5–48. Koblížek, J., Sutorý, K., Řepka, R., Unar, J. & Ondráčková, S. 1998. Floristická charakteristika vybraných lokalit širšího okolí energetické soustavy Dukovany-Dalešice [Floristic characterization of selected localities in a broader surroundings of the power system Dukovany-Dalešice]. Přírodovědný sborník Západomoravského muzea v Třebíči 37: 1–99. Rosa canina Rumex acetosella Salvia pratensis Sanguisorba minor Saxifraga bulbifera Scabiosa canescens Scabiosa ochroleuca Scleranthus annuus Scorzonera austriaca Securigera varia Sedum acre Sedum album Sedum sexangulare Senecio erucifolius Senecio jacobaea Senecio viscosus Seseli hippomarathrum Seseli osseum Silene otites Silene vulgaris Sorbus aucuparia Stachys recta Stipa capillata Stipa dasyphylla Stipa pennata Stipa pulcherrima Stipa tirsa Taraxacum sect. Erythrosperma Taraxacum sect. Taraxacum Teucrium chamaedrys Thymus praecox Tragopogon orientalis Trifolium alpestre Trifolium arvense Trifolium campestre Trifolium dubium Trifolium repens Verbascum chaixii subsp. austriacum Verbascum lychnitis Verbascum phoeniceum Verbascum thapsus Veronica arvensis Veronica prostrata Veronica vindobonensis Veronica spicata Vicia tenuifolia Vincetoxicum hirundinaria Viola rupestris Viscaria vulgaris Forest species Abies alba Acer campestre Acer platanoides Acer pseudoplatanus Actaea spicata Adoxa moschatellina Aegopodium podagraria Ajuga reptans Alliaria petiolata Anemone nemorosa Angelica sylvestris Anthriscus sylvestris Asarum europaeum Asplenium cuneifolium Astrantia major Athyrium filix-femina Avenella flexuosa Betula pendula Brachypodium pinnatum Brachypodium sylvaticum Bupleurum falcatum Calamagrostis arundinacea Campanula persicifolia Campanula rapunculoides Campanula rotundifolia agg. Campanula trachelium Cardamine impatiens Carex digitata Carex humilis Carex muricata agg. Carpinus betulus Cephalanthera damasonium Chaerophyllum temulum Chelidonium majus Convallaria majalis Cornus mas Cornus sanguinea Corydalis solida Corylus avellana Crataegus spp. Cyclamen purpurascens Cytisus nigricans Dactylis polygama Dryopteris carthusiana Dryopteris filix-mas Elymus caninus Epilobium montanum Epipactis helleborine Euonymus europaeus Euonymus verrucosus Euphorbia dulcis Festuca gigantea Festuca ovina Ficaria verna subsp. verna Fragaria moschata Fragaria vesca Fraxinus excelsior Galeobdolon montanum Galium odoratum Galium sylvaticum Genista pilosa Genista tinctoria Geranium robertianum Geum urbanum Hepatica nobilis Hieracium laevigatum Hieracium murorum Hieracium sabaudum Hypericum montanum Hypericum perforatum Impatiens noli-tangere Impatiens parviflora (neo) Knautia drymeia Lactuca viminea Ligustrum vulgare Lilium martagon Lonicera xylosteum Luzula divulgata Luzula luzuloides Melampyrum pratense Melica nutans Melica uniflora Mercurialis perennis Moehringia trinervia Monotropa hypophegea Mycelis muralis Myosotis sylvatica Neottia nidus-avis Noccaea montana Omphalodes scorpioides Oxalis acetosella Phyteuma spicatum Picea abies Pilosella officinarum Pinus sylvestris Poa angustifolia Poa nemoralis Polygonatum multiflorum Polygonatum odoratum Polypodium vulgare Populus tremula Primula veris Prunus avium Pulmonaria obscura Pulmonaria officinalis Quercus petraea Quercus robur Rhamnus cathartica Rosa canina Rubus fruticosus agg. Sambucus nigra Scrophularia nodosa Senecio ovatus Sesleria caerulea Silene nutans Solidago virgaurea Sorbus aucuparia Stachys sylvatica Stellaria holostea Symphytum tuberosum Tanacetum corymbosum Tilia cordata Tilia platyphyllos Trifolium alpestre Ulmus glabra Urtica dioica Vaccinium myrtillus Veronica chamaedrys 3 74 75 Kolář, F. & Vít, P. 2008. Endemické rostliny českých hadců 1. Zvláštnosti hadcových ostrovů [Endemic plants of the Czech serpentinites 1. Peculiarities of the serpentinite islands]. Živa 56: 14–17. Quitt, E. 1996. Změny mikroklimatu a topoklimatu způsobené výstavbou vodních nádrží Dalešice a Mohelno [Changes in microclimate and topoclimate caused by the construction of the Dalešice and Mohelno water reservoirs]. Přírodovědný sborník Západomoravského muzea v Třebíči 21: 1–26. Suza, J. 1928. Geobotanický průvodce serpentinovou oblastí u Mohelna na jihozápadní Moravě (ČSR) [Geobotanical guide through the serpentinite area near Mohelno in south-western Moravia (Czechoslovakia)]. Rozpravy České akademie věd a umění, Třída II (Mathematicko-přírodovědecká) 37 (31): 1–116. Unar, J. 1996. Přehled druhové skladby dřevinné a bylinné vegetace NPR Mohelenská hadcová step [Overview of the species composition of woody and herbaceous vegetation in the Mohelenská hadcová step National Nature Reserve]. Přírodovědný sborník Západomoravského muzea v Třebíči 23: 1–44. Veselý, P. 2002. Mohelenská hadcová step – historie vzniku rezervace a jejího výzkumu [Mohelno Serpentinite Steppe – the history of the reserve establishment and its research]. Brno. Vicherek, J. 1970. Ein Beitrag zur Syntaxonomie der Felsspalten- und Rissenpflanzengesellschaften auf Serpentin in Mitteleuropa. Folia Facultatis Scientiarum Naturalium Universitatis Purkynianae Brunensis 11(3): 83–89. 4 Krumlov-Rokytná Conglomerates Pavel Novák Introduction The Krumlov-Rokytná Conglomerates (Krumlovsko-rokytenské slepence) National Nature Reserve was established in 2005 to protect the dry grasslands, rock outcrops and forests of the Rokytná River Valley north-east of the town of Moravský Krumlov, about 30 km SW of Brno. The reserve is comprised of two parts which in total cover an area of 87 ha at altitudes between 220 and 340 m. It is situated on the north-western edge of the Pannonian Province in southern Moravia and contains various vegetation types with many rare (especially thermophilous) plant species. The southern part of the reserve surrounds a meander with the historical town of Moravský Krumlov with its picturesque sixteenth-century Renaissance castle, remains of the old town fortification, several churches and the remarkable Baroque pilgrimage Chapel of St. Florian from 1697 situated on the upper edge of the reserve. Summer view of dry grassland with blooming Allium senescens subsp. montanum. This vegetation is frequently developed on the red Carboniferous-Permian conglomerate on the steep sunny slopes of the Rokytná Valley above the historical town of Moravský Krumlov. Photo P. Novák. Geology, soils and climate The site includes a deep river valley with steep rocky slopes, numerous rock outcrops and small screes. The prevailing bedrock type is the Carboniferous-Permian red conglomerate containing mostly acidic gravel clasts within a matrix of a fine-grained calcareous sediment which has supported the development of mixed acidophilous and basiphilous flora and vegetation. Quaternary alluvial and colluvial sediments occur along the Rokytná River meandering along the valley bottom. Cambisols are the 4