A nature reserve was declared in the area along the streams of Bystřina and Lužní potok in the remotest part of the Aš headland adjoining the German border in 1992. The total area of the reserve on the territory of the Czech Republic is 50 hectares and its elevation ranges from 540 to 625 metres above sea level. The main reason for establishing the reservation was to conserve the biotope of the rare freshwater pearl mussel (Margaritifera margaritifera) due to existing concerns that removal of the "Iron Curtain" and the opening of the border regions could jeopardize its occurrence. The freshwater pearl mussel is a critically endangered animal species in both the Czech Republic and neighbouring Germany and the two brooks and their tributaries are one of its last habitats in Central Europe. There are only five freshwater pearl mussel localities in the Czech Republic. The Bystřina Nature Reserve and the Lužní potok National Nature Monument is a concrete example of co-operation of Czech and German conservationists who have combined their experience with the aim of saving the freshwater pearl mussel and establishing a protected area on both sides of the border.
The planned opening of the Hranice – Ebmath border crossing for motor vehicles and the building of a petrol station could pose a threat to this Site of Community Significance.
Both the brooks, which are characterised by nutrient deficiency (oligotrophic), are home to the rare mollusc – i.e. the freshwater pearl mussel, the occurrence of which depends on complex environmental relationships within the whole basin. The freshwater pearl mussel requires oligotrophic waters in which it feeds on water detritus (semi-decomposed biomass). Water stability is secured by forest and meadow biotopes along the brooks and the basin. However, this is not sufficient for the successful reproduction of the mollusc as the presence of the brown trout (Salmo trutta morpha fario) or the Atlantic salmon (Salmo salar) is essential for larval development – the larvae develop in their branchiae for a certain period of time. Thus, it is necessary to preserve the brooks and the whole alluvial plain along with the spring area. Apart from the freshwater pearl mussel, other critically endangered species include the European brook lamprey (Lampetra planeri) and the European crayfish (Astacus astacus).
Additional valuable animal species inhabiting the Bystřina – Lužní potok locality is the Marsh fritillary (Euphydryas aurinia), which may be also found in Slavkovský les (Slavkov Forest). Caterpillars of this butterfly feed and develop on a single flowering plant in West Bohemia known as the Devil's bit (Succisa pratensis). Even if the Devil's bit does not belong among endangered plant species, it should be subject to protection with a view of its correlation to the occurrence of the rare butterfly species. The site is also the nesting area of the endangered black stork (Ciconia nigra) and Eurasian pygmy owl (Glaucidium passerinum).
The first in-depth botanical research of the area was conducted in 1994 and based on its findings, the area was extended in 1998. As regards wild flora species subject to special protection the area is the habitat of the critically endangered heath milkwort (Polygala serpyllifolia) and bog pondweed (Potamogeton polygonifolius). Highly endangered species include lousewort (Pedicularis sylvatica) and round-leaved sundew (Drosera rotundifolia). Occurrence of the alpine pondweed (Potamogeton alpinus) was revealed in 2005. The site is also the habitat of endangered species – e.g. arnica (Arnica montana), western-marsh orchid (Dactylorhiza majalis), marsh pennywort (Hydrocotyle vulgaris), bogbean (Menyanthes trifoliata), cranberry (Oxycoccus palustris) and creeping willow (Salix repens). As to species less frequent in the Cheb district, which are not included among endangered species in the Czech Republic, we may find such species as the wood betony (Betonica officinalis), water avens (Geum rivale), columbine meadow rue (Thalictrum aquilegiifolium); as well as the thermophilic tor grass (Brachypodium pinnatum).