Academic journal article Estonian Journal of Ecology

Bryophytes in Estonian Mires

Academic journal article Estonian Journal of Ecology

Bryophytes in Estonian Mires

Article excerpt

INTRODUCTION

Almost a quarter of Estonia's terrestrial area is covered by peatlands. Peatland is an area with or without vegetation with a naturally accumulated peat layer at the surface (Joosten and Clark, 2002). Mire is a peatland with a peat layer of at least 30 cm depth, which is in a continuous process of development (Paal and Leibak, 2011). Only about 5.5% of the Estonian territory is covered by different types of mires (open or with a scattered low tree layer), and 17% is covered by paludified (peat layer less than 30 cm) and peatland forests (peat layer more than 30 cm) and degraded peatlands (Paal and Leibak, 2011). Draining for agriculture and other uses as well as peat excavation have diminished the past mire areas significantly. The area of mires in Estonia declined approximately by 36% in the recent 60 years; the most drastic change is seen in floodplain fens, whose area diminished 28 times (Paal and Leibak, 2011). The situation in the whole of Europe is even worse, 62% of its former mire area is lost (Raeymaekers, 2000). Many mire types are already very rare in Europe and the remaining areas are in urgent need to be preserved (Habitat Directive, 1992). Land use and climate change are the major threats to the existence of mires and mire plants causing extinction or diminishing the distribution of many mire bryophyte species.

Knowledge on the species diversity in different communities and their demands for the community properties are indispensable for improving management planning and nature protection. We have a list of Estonian hemerophobic forest bryophyte species (Trass et al., 1999), also lists of indicator species for Estonian woodland key habitats of different forest communities (RT, 2010), but there is no up-to-date list of Estonian mire bryophytes, although bryophytes are the main components in mires and in peat. A preliminary list of bryophytes of Estonian peatlands was published 42 years ago (Kannukene and Kask, 1982). Since then several papers including data about mire bryophytes have been published, and numerous mire bryophyte specimens have been accumulated in Estonian herbaria (TU, TAA, TAM, TALL). A database of Estonian biodiversity (eElurikkus), established in 2008 and continuously complemented, includes information on records of different recent case studies of mires. During the last 20 years several mire inventories have been carried out on the whole territory of Estonia and data sheets with species lists and community-level evaluations have been compiled.

The aim of this study is to present an updated list of mire bryophytes and their community preferences, and to highlight threatened mire species in Estonia.

MATERIAL AND METHODS

For compiling an updated list of Estonian mire bryophytes we checked the former list, published sources listed in Nurkse (2011), herbarium specimens from TU, TAA, and TAM, the database of Estonian biodiversity with 8742 records (eElurikkus), and data sheets for more than 8676 mires deposited in the Estonian Fund of Nature. The nomenclature of species was updated according to Hill et al. (2006) and Soderstrom et al. (2007). The species were grouped into main mire types used in Estonia (Laasimer and Masing, 1995): fen, transitional mire, and bog. Fen is a minerotrophic mire, fed mainly by groundwater, and divided into poor and rich fens; bog is ombotrophic, fed by precipitation; transitional mire is mixotrophic, fed on hummocks by precipitation and in depressions by groundwater. The list is restricted with open communities and wet forest types are excluded.

The occurrence frequency (Table 1) of obligatory mire species was estimated on the basis of species frequency in Estonia (http://www.botany.ut.ee/bruoloogia/), records in the literature and herbaria, and field experience of the authors. The following notation is used: C--common, more than 20 localities in Estonia; R--rare, less than 20 localities in Estonia. …

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