Krumlovsko – rokytenské slepence National Nature Reserve

Krumlovsko–rokytenské slepence NNR (The Krumlov – Rokytná Conglomerates) was declared in 2005 and covers a complex of forest stands with scattered areas of steppe, forest steppe and rock vegetation lies 0.5 km east of the town of Moravský Krumlov in the Jihomoravský kraj - South Moravian region. The reserve covers an area of 86.58 ha at elevations of 220 – 336 metres above sea level. The subject of the protection is the unique plant and animal communities which are bound to the specific geomorphological and microclimatic conditions of the rugged Rokytná stream valley.

The territory belongs to the Rokytenská pahorkatina hilly land, which is cut through by the deep valley of the Rokytná stream with its sunken meanders. The terrain is very rugged and the river has formed several meanders, the largest of which are in Moravský Krumlov and around the village of Rokytná, where they give the impression of natural rocky amphitheatres. Slopes with various orientations and gradients can be found in the territory as well as numerous rocky outcrops and cliffs, which combine with the varying soil chemistry to create the conditions for the formation of a number of differing plant communities on a relatively small area.

The substrate is formed of Permian conglomerates (called Rokytná conglomerates). In places the Permian sediments are covered by Quaternary sediments, especially Holocene fluvial deposits from the Rokytná stream. River terraces have developed on the outer banks of meanders and extensive colluvial accumulations are found at the slope bases. The cement of the Rokytná conglomerates is characterized by its slightly basic reaction and this makes it different from other conglomerates in the surroundings of Brno. This alkalinity is reflected in the greater occurrence of basiphyte plant species here.

Cambisols are the predominant soil type, with rendzinas and rankers on small areas. Fluvisols are found on the Rokytná alluvial plain.

The forested areas in the reserve consist predominantly of thermophilous oakwoods of the Corno-Quercetumassociation, with oakwoods of the Sorbo torminalis-Quercetum association on decalcified areas. The forest fringes are of the Geranio-Dictamnetum association. Low scrub of the Prunetum fruticosae association can also be found here, in addition to the predominant rocky steppe of the Medicagini prostratae-Festucetum pallentis association (Alysso-Festucion pallentis). Relict lime stands of the Sesleri albicantis-Tilietum cordatae association can be found on the upper edge of the north-facing slope with moor-grass grasslands of the Diantho moravici-Seslerietum albicantis association (Diantho lumnitzeri-Seslerion alliance) and cotoneaster scrub of the Junipero communis-Cotoneastretum integerrimae association on the steep slopes. Oak-hornbeam stands of the Melampyro nemorosi-Carpinetum association grow on the colluvia at the foot of the slopes and ash-alder alluvial stands (Stellario-Alnetum glutinosae) can be found on the alluvial plain of the river.

The vegetation on the rocks, forest steppe, forest and forest fringe areas of the NNR has a very high species diversity and includes a whole range of protected and endangered species. Among the most notable vascular plants are the endemic Moravian pink (Dianthus moravicus), as well as northern rockcress (Cardaminopsis petraea), the fenugreek Trigonella monspeliaca, the buttercup Ranunculus illyricus, the dwarf iris - Iris pumila, yellow monkshood (Aconitum anthora) and common fumana (Fumana procumbens). The forest communities of oak-hornbeam stands, white oak stands and relict lime stands are also of great value and have been preserved with an almost natural species composition. All of the oaks (Quercus sp.) which grow naturally in the Czech Republic can be found here in the reserve. The NNR is an area of exceptional botanical value with the largest population of the Moravian pink (Dianthus moravicus) and several strong populations of greater pasque flower (Pulsatilla grandis).
Invertebrates with strong populations in the reserve include the praying mantis (Mantis religiosa) as well as southern festoon (Zerynthia polyxena), the owl-fly (Libelloides macaronius), the jewel beetle Anthaxia hungarica, great Capricorn beetle (Cerambyx cerdo) and the critically-endangered painter’s mussel (Unio pictorum) has been found in the protected section of the Rokytná river. Legally protected vertebrate species in the reserve include the reptiles: emerald lizard (Lacerta viridis), smooth snake (Coronella austriaca), grass snake (Natrix natrix) and the amphibians: common toad (Bufo bufo). The bird populations here include the corn bunting (Miliaria calandra), quail (Coturnix coturnix), barn owl (Tyto alba), hoopoe (Upupa epops), eagle owl (Bubo bubo) and raven (Corvus corax).
The majority of the NNR territory was extensively used for forestry in the past. Due to the difficult access to the steep slopes these areas were never clear-cut but only individual trees were felled. The result is the current mixed-age forest stands with a near natural species composition. Non-native tree species such as false acacia (Robinia pseudoacacia) were planted in areas next to the reserve but with the exception of the “Tábor” locality, they are not spreading into the NNR territory.
Part of the territory was agriculturally used as small vineyards, arable land and pastures. After agricultural usage of these areas came to an end, they were gradually overgrown by trees and shrubs. In some areas this succession is naturally blocked by abiotic factors such as lack of water. At present we are gradually removing woody plants from the formerly forest-free areas and managing the grasslands by hand-cutting them at different times in different areas. Non-native trees and shrubs are removed from areas with high potential for the renewal of naturally valuable communities and also from areas which are endangered by invasive trees. In the future it will be necessary to continue the gradual, sensitive and small-area renewal of forest communities and especially the coppice stands.