Diversity of lichens in semi-natural habitats of Estonia
Date
2013-11-12
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Abstract
Pika traditsiooniga Eesti poollooduslikud kooslused – puisniidud ja loopealsed (alvarid) – on looduskaitse seisukohalt olulised kui omapärase ja liigirikka samblikuelustiku, sealhulgas haruldaste ja kaitset väärivate samblike elupaigad. Kahjuks on need poollooduslikud kooslused nii Eesti kui kogu Euroopa kultuurmaastikult kadumas, mis on tingitud eelkõige traditsioonilise majandamisviisi lakkamisest. Puisniidud on võsastunud või haritud üles põllumaaks ning looniidud ja -karjamaad on asendunud tihedate kadastikega, kuna loomade karjatamine madala produktiivsusega alvaritel pole eriti tulus. Puisniitude võsastumise ja kinnikasvamise tulemusel on muutunud sealsed klimaatilised tingimused, eelkõige valgustingimused. See omakorda on muutnud ja vaesustanud puisniitudele omaseid epifüütseid samblikukooslusi. Valgusnõudlikud liigirikkad samblikukooslused on asendunud liigivaeste varju taluvate samblike kooslustega. Et säilitada või taastada epifüütide liigirikkust puisniidul, tuleks luua võimalikult heterogeensed tingimused. Säilitada tuleks puisniitude mosaiikset poolavatud struktuuri jättes kasvama erinevaid puude- ja põõsastegruppe. Puid ja järelkasvu tuleks raiuda valikuliselt, jättes kasvama eri vanuses ja erinevat liiki puid. Traditsiooniline puisniitude majandamine hõlmab ka niitmist või karjatamist, mis tagab puisniidu avatud struktuuri.
Ka loopealsete maapinnasamblikud on mõjutatud traditsioonilise majandamise (karjatamise, kadakate harvendamise) lakkamisest. Maapinnasamblike liigirikkus väheneb ja liigiline koosseis muutub rohu- ja põõsarinde katvuse suurendes. Muutub ka samblike kasvuvormide proportsioon, koorikja ja soomusja kasvuvormiga liigid asenduvad põõsasja kasvuvormiga liikidega. Rohu- ja põõsarinde pealetungi suhtes on eriti tundlikud haruldased ja kaitset väärivad liigid. Loopealsete samblikele alternatiivsed kasvukohad, nagu vanad lubjakivikarjäärid, endised sõjaväealad või nurjunud metsastamise katsega jäätmaad, on kujunenud loopealsete samblikele omamoodi ajutisteks asendusaladeks või refuugiumiteks. Seetõttu võiks loopealsete taastamisel ja majandamisel rakendada lisaks traditsioonilistele majandamisvõtetele (karjatamine ja kadakate harvendamine) ka drastilisemaid võtteid nagu mullapinna laiguti eemaldamine aluspõhjani välja.
Semi-natural habitats with long management history, wooded meadows and alvars in northern Europe, are of great importance for nature conservation according to their high contribution to biodiversity including rare, red-listed, and protected lichens for the studied region. Unfortunately these habitats are disappearing from our cultural landscape, mainly due to the cessation of traditional management; they are replaced by cultivated fields or abandoned to brushwoods. The study demonstrates that abandonment of wooded meadows causes changes in stand structure and in the openness of wooded meadows, which impoverishes and alters epiphytic lichen community. Light-demanding lichen communities, rich in foliose and fruticose lichens, will be replaced with impoverished shade-tolerant crustose lichen dominated communities due to encroachment of wooded meadows with trees and shrubs. To support diverse epiphytic lichen communities trees and undergrowth should be cut selectively, retaining a mosaic of semi-open structure of wooded meadows with trees of various species and age classes, and some clumps of bushes. Annual mowing or grazing is important for preserving this semi-open structure. Similarly, epigeic lichen communities of semi-natural alvar grasslands are strongly affected by cessation of grazing and cutting of junipers. With the increasing herb and shrub cover, the species richness of epigeic lichens diminishes, species composition alteres and the proportions of species growth forms change (crustose and squamulose species are replaced with fruticose species). Lichens with a conservation value, especially rare species, are particularly sensitive to the abandonment-induced encroachment of herbs and shrubs. Old abandoned limestone quarries, former military areas or wastelands of failed afforestation attempts appeared to be alternative or temporary substitution habitats (refugia) for ground layer lichens including lichens with a high conservation value. Therefore, in addition to conventional recommendations for alvar restoration including moderate grazing and removal of shrubs, it is suggested to promote small-scale ground cover disturbances and patchy peeling off of the soil layer to expose base rock.
Semi-natural habitats with long management history, wooded meadows and alvars in northern Europe, are of great importance for nature conservation according to their high contribution to biodiversity including rare, red-listed, and protected lichens for the studied region. Unfortunately these habitats are disappearing from our cultural landscape, mainly due to the cessation of traditional management; they are replaced by cultivated fields or abandoned to brushwoods. The study demonstrates that abandonment of wooded meadows causes changes in stand structure and in the openness of wooded meadows, which impoverishes and alters epiphytic lichen community. Light-demanding lichen communities, rich in foliose and fruticose lichens, will be replaced with impoverished shade-tolerant crustose lichen dominated communities due to encroachment of wooded meadows with trees and shrubs. To support diverse epiphytic lichen communities trees and undergrowth should be cut selectively, retaining a mosaic of semi-open structure of wooded meadows with trees of various species and age classes, and some clumps of bushes. Annual mowing or grazing is important for preserving this semi-open structure. Similarly, epigeic lichen communities of semi-natural alvar grasslands are strongly affected by cessation of grazing and cutting of junipers. With the increasing herb and shrub cover, the species richness of epigeic lichens diminishes, species composition alteres and the proportions of species growth forms change (crustose and squamulose species are replaced with fruticose species). Lichens with a conservation value, especially rare species, are particularly sensitive to the abandonment-induced encroachment of herbs and shrubs. Old abandoned limestone quarries, former military areas or wastelands of failed afforestation attempts appeared to be alternative or temporary substitution habitats (refugia) for ground layer lichens including lichens with a high conservation value. Therefore, in addition to conventional recommendations for alvar restoration including moderate grazing and removal of shrubs, it is suggested to promote small-scale ground cover disturbances and patchy peeling off of the soil layer to expose base rock.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
puisniidud, loopealsed, samblikud, bioloogiline mitmekesisus, Eesti, wooded meadows, alvars, lichenes, biodiversity, Estonia