If fire occurs in a transitional mire, the lower microhabitats (lawns, carpets) usually do not suffer very much and will recover comparatively quickly, but hummocks of sphagna together with dwarf shrubs may be destroyed seriously and their recovering can take several decades as in case of raised bogs. During the last decades, fires have had noticable impact in Läänemaa Suursoo (western Estonia), Feodorisoo (northeastern Estonia), Varnja soo (eastern Estonia) and, to a lesser extent, in some other mires. Some of the burnt bogs have been objects of relevant monitoring.
5.10 Long-term effects Some serious effects of the former extensive drainage will appear only decades later. That concerns especially successional changes of mire vegetation structure due to lowering of the water table in the surrounding areas: even in protected mires the characteristic communities will be replaced by others, having a simple structure. In that way communities of several types as well as numerous plant and animal species turn to be threatened and rare. In western Estonia the fen flora and vegetation has been intensively studied in 1948–1955 and re-studied in 1991–1992. On this basis it is possible to characterize the main trends in the composition of flora during the last 35–40 years, mainly due to the amelioration in neighboring areas. According to Trass (1994), four groups of species should be distinguished: (i) species with unchanged frequency: Juncus subnodulosus, Myrica gale, Rhinanthus rumelicus subsp. osilinensis, Cladium mariscus, and several common obligate telmatophytes such as Potentilla palustris, Peucedanum palustre, Carex lasiocarpa, C. elata, etc.; (ii) species with incresed frequency: Molinia caerulea, Deschampsia cespitosa, Carex nigra, C. panicea, C. canescens, Epipactis palustris; (iii) species with slightly declined frequency: Tofieldia calyculata, Carex buxbaumii, C. hostiana, C. davalliana, C. heleonastes, Eriophorum gracile, Schoenus ferrugineus, Liparis loeselii, Hammarbya paludosa, Drosera intermedia, Saussurea alpina subsp. esthonica, Pedicularis sceptrum-carolinum, Utricularia minor, Equisetum variegatum, Euphorbia palustris; (iv) species with frequency fallen to the critical limit: Gymnadenia odoratissima, Selaginella selaginoides, Pinguicula alpina, Malaxis monophyllos. Notable changes had taken place also in fen vegetation. Trass (1994) has established five change-groups: (i) communities met on approximately as large an area and with the same frequency as 35–40 years ago: Phragmitetum australis, Drepanoclado–Caricetum lasiocarpae, Scorpidio–Caricetum lasiocarpae, Caricetum diandrae, Cladietum marisci, Primulo–Seslerietum, Caricetum cespitoso–appropinquatae, Caricetum flavae, Caricetum acutae, Juncetum subnodulosi, Equisetetum fluviatilis; (ii) communities the area of which has diminished to some extent (mostly only for some hecatares on certain fen): Drepanoclado–Schoenetum, Caricetum hostianae, Caricetum dioicae, Caricetum elatae, Caricetum vesicariae, Schoenetum nigricantis, Eriophoretum polystachionis, Scorpidio–Schoenetum, Menyantheto–Caricetum limosae; (iii) communities the area of which has considerably decreased (for hundreds or even thousands hectares, or if the community type is rare, more than 50%): Caricetum davallianae, Caricetum buxbaumii; (iv) communities the area of which has somewhat increased (on some fens for tens or hundreds of hectares): Myrico–Schoenetum, Seslerio–Caricetum paniceae, Calamagrostietum canescentis, Caricetum paniceo–nigrae, Myrico–Betuletum pubescentis; (v) communites the area of which has remarkably increased (for hundreds or thousands of ESTONIAN MIRES: INVENTORY OF HABITATS
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