After abandonment, dry grassland (Festuco-Brometea) areas decline due to gradual overgrowing by woody species and the expansion of perennial tall grass species. Dry grassland vegetation was formed by extensive livestock grazing, thus grazing is considered one of the most natural methods for managing this type of vegetation. Six years after introducing low-intensity sheep and goat grazing in seven nature reserves in Prague (Czech Republic), the following impact of this management on dry grassland vegetation was observed: The cover of expansive woody species, particularly Ligustrum vulgare, and to a smaller extent Cornus sanguinea and Prunus spinosa declined. In addition, a significant, long-term declining trend of the expansive species Arrhenatherum elatius was also observed. Also the cover of Pimpinella saxifraga and Allium senescens declined significantly with regard to statistical evaluation. On the contrary, the cover of Achillea millefolium, Centaurea stoebe, Securigera varia, Elytrigia repens, Erysimum crepidifolium, Falcaria vulgaris, Fallopia convolvulus and Verbascum lychnitis increased. The cover of species characteristic of dry grasslands (Festuco-Brometea) increased significantly. No changes were observed in the number and cover of the Red List species. In addition, the presence of nitrophilous and ruderal species increased. Species diversity also significantly increased. From our findings we can conclude that managing dry grasslands with lowintensity grazing can help to keep dry grassland vegetation in good condition and conserve its plant diversity. Nomenclature: Kubát et al. (2002) for taxa and Moravec et al. (1995) for syntaxa.

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The work summarizes and discusses the basic conditions and rules for the use of the deductive method of syntaxonomic classification. This method develops and supplements classification procedures of the Braun-Blanquet approach. It enables to classify the communities which cannot be characterized by their own character-and differential-species. The deductive method incorporates into the inductively constructed system of abstract units of the Braun-Blanquet approach (classes, orders, alliances and associations) really existing communities on the basis of the presence or absence of diagnostic characters (character-and differential-species) of these abstract units. Some communities are incorporable only at the class level, others at the level of lower units.To objectify the process of incorporation of the communities represented by the respective phytocoenological relev6s, an algorithm of the deductive method was constructed which uniquely incorporates individual relev6s and groups of relev6s into the phytocoenological system on the basis of the presence, coverage and diagnostic value of species. The work includes a detailed description of this algorithm and examples of its application on concrete phytocoenological material. Examples of hitherto use of the deductive method are also discussed and its nomenclatural rules briefly explained.

Abstract:The landscape of the Czech Republic currently faces droughts that are caused by several factors. One of the reasons for drought is landscape development and land cover changes. Changes in water and wetland areas and streams were studied by comparing old military maps and the present state. Water and wetland areas in fertile lowlands significantly decreased over time; the landscape was continuously dried out with the aim of increasing agricultural and woody production. While water and wetland areas occupied nearly one-third of the study area (Nové Dvory and Žehušice micro-regions in Central Bohemia) at the end of the 18 th century, the present share of these areas is only 3.5%. There was a decrease of approximately 10% in each period, and nearly all of these areas disappeared by the end of the 19 th century. Water and wetland areas were changed primarily to arable land. The length of streams decreased by the end of the 19 th century. Drainage and irrigation channels were built during the 20 th century, and although they are only periodic or episodic streams, these channels increased the total length of streams.Key words: streams, still waters, wetlands, land use changes, drought, central Europe Abstrakt: Krajina České republiky v současnosti čelí nebezpečí sucha, které je způsobeno mnoha faktory. Mezi ně patří změny krajiny a krajinného pokryvu. V článku jsou sledovány změny vodních a mokřadních ploch a délky vodních toků na podkladě starých vojenských mapování a současného stavu. Vodní a mokřadní plochy v nížinách zásadně ubyly a krajina byla vysušována s cílem zvýšit zemědělskou a lesnickou produkci. Zatímco na konci 18. století vodní a mokřadní plochy zaujímaly skoro třetinu sledovaného území Novodvorska a Žehušicka ve středních Čechách, v současnosti je to jen 3,5 %. V každé ze sledovaných period ubylo přibližně 10 % jejich rozlohy, významný úbytek těchto ploch v krajině tak nastal již v 19. století. Vodní a mokřadní plochy byly změněny převážně na ornou půdu. Délka vodních toků poklesla zejména v průběhu 19. století. Současná data ukazují nárůst jejich délky, který je ale způsoben budováním zavodňovacích a odvodňovacích kanálů, jejichž délka je také započítána do celkové délky vodních toků, byť nejsou celoročně protékány vodou.