Plant diversity of semi-natural grasslands: drivers, current status and conservation challenges
Kuupäev
2017-08-15
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Abstrakt
Suur osa Euroopa soontaimede liigirikkusest on seotud pool-looduslike niidukooslustega ning väikesel skaalal (nt. 10x10 cm) on nad erakordselt liigirikkad ka kogu maailma mastaabis. Alates 20. sajandi algusest on aga kogu Euroopas inimasustuse tihenemise, põllumajanduse intensiivistumise ning karjatamise ja niitmise lakkamise tõttu nende pindala ja kvaliteet drastiliselt vähenenud. Tänaseks on selge, et niitude elurikkuse säilitamiseks on vaja ökoloogilistel teooriatel põhinevat looduskaitset. Oma doktoritöös tegin kindlaks, millised tegurid on taganud kuivade lubjarikaste niidukoosluste kõrge soontaimede liigirikkuse. Tulemused näitavad, et liigirikaste niitude teke ja püsimine sõltub nii suurekaalalistest teguritest nagu pidev mõõdukas majandamine, piisava hulga niidulaikude olemasolu ja sidusus maastikus kui ka kohalikest keskkonnatingimustest, mida tuleb arvesse võtta elupaikade taastamisel ja säilitamisel. Lisaks hindasin Kesk- ja Põhja-Euroopa kuivade kuni parasniiskete niitude praegust seisundit ning pakkusin välja uusi soovitusi rohkemal või vähemal määral degradeerunud koosluste taastamiseks ja nende elurikkuse säilitamiseks. Kümnest uuritud piirkonnast kuues olid osad niiduspetsialistidest taimeliigid juba kadunud ning koosluses esines suuremal hulgal generaliste. Alles jäänud niiduspetsialistidel oli oluliselt madalam levimisvõime. Neljas uuritud piirkonnas olid kõik liigid veel alles, seega tuleks seal võimalikult kiiresti alustada elupaiga taastamisega, et takistada hea levimisvõimega niiduspetsialistide kadumist ja uute generalistide saabumist. Niidulaikudes, kus liigid juba kadunud ja elupaiga kvaliteet oluliselt vähenenud, on täielik koosluse taastamine keerulisem ja ajaloolise seisundi saavutamine vähem tõenäoline. Samas on sellised degradeerunud ja algsest kooslusest oluliselt teisenenud elupaigalaigud tihtipeale siiski liigirikkad, toetades vähemalt osaliselt ajalooliste niitude elustikku. Seega tuleks kaaluda selliste liigirikaste, samas tugevalt degradeerunud koosluste majandamist ja säilitamist hübriidsete või uudsete kooslustena, mis hoiaks ära nende edasise seisundi halvenemise ja annaks panuse piirkonna elurikkuse säilimisele. Prioriteediks peab aga alati siiski seadma looduslike ja pool-looduslike koosluste taastamise ja säilitamise
Semi-natural grasslands harbour a large part of Europe’s biodiversity and hold the records for highest small-scale (e.g. 10x10 cm) plant species richness in the world. During the past century, ca. 90% of the grassland area has been lost due to the urbanization, intensification of agriculture and cessation of traditional management, rendering many species vulnerable to local extinctions. Habitat restoration and conservation, based on the ecological theories, is needed for successful biodiversity protection. My thesis covered the shortcomings in the knowledge of which factors determine the high plant species richness in semi-natural dry calcareous grasslands. I found that species richness is dependent on historical habitat area and connectivity as well as suitable local environmental conditions, indicating the importance of considering both landscape- and local-scale factors in habitat restoration and conservation. I also assessed the status of dry to mesic grasslands in central and northern Europe, and provided implications for biodiversity restoration and conservation of communities with different level of degradation. I found that in six studied regions, specialist species susceptible to habitat loss have gone already extinct and communities consisted more habitat generalists. Remaining specialists appeared to have considerably lower dispersal ability. In four regions, specialist species still temporally persist despite of the unfavourable habitat conditions. Habitat restoration is urgently needed in those regions, to prevent the loss of good dispersers and infiltration of generalist species. In grassland systems where the habitat quality has considerably decreased and susceptible species have gone already extinct, complete restoration to historical state may not be successful. Therefore, instead of attempting their restoration to historical state or continuing their abandonment, it would be perhaps worthwhile to consider managing and maintaining such habitats as hybrid or novel ecosystems (i.e. habitats out of their historical range) as they are often still species-rich and can contribute to the local biodiversity protection. However, the priority must be set to restoration and preservation of historically developed habitat types
Semi-natural grasslands harbour a large part of Europe’s biodiversity and hold the records for highest small-scale (e.g. 10x10 cm) plant species richness in the world. During the past century, ca. 90% of the grassland area has been lost due to the urbanization, intensification of agriculture and cessation of traditional management, rendering many species vulnerable to local extinctions. Habitat restoration and conservation, based on the ecological theories, is needed for successful biodiversity protection. My thesis covered the shortcomings in the knowledge of which factors determine the high plant species richness in semi-natural dry calcareous grasslands. I found that species richness is dependent on historical habitat area and connectivity as well as suitable local environmental conditions, indicating the importance of considering both landscape- and local-scale factors in habitat restoration and conservation. I also assessed the status of dry to mesic grasslands in central and northern Europe, and provided implications for biodiversity restoration and conservation of communities with different level of degradation. I found that in six studied regions, specialist species susceptible to habitat loss have gone already extinct and communities consisted more habitat generalists. Remaining specialists appeared to have considerably lower dispersal ability. In four regions, specialist species still temporally persist despite of the unfavourable habitat conditions. Habitat restoration is urgently needed in those regions, to prevent the loss of good dispersers and infiltration of generalist species. In grassland systems where the habitat quality has considerably decreased and susceptible species have gone already extinct, complete restoration to historical state may not be successful. Therefore, instead of attempting their restoration to historical state or continuing their abandonment, it would be perhaps worthwhile to consider managing and maintaining such habitats as hybrid or novel ecosystems (i.e. habitats out of their historical range) as they are often still species-rich and can contribute to the local biodiversity protection. However, the priority must be set to restoration and preservation of historically developed habitat types
Kirjeldus
Väitekirja elektrooniline versioon ei sisalda publikatsioone
Märksõnad
pärandkooslused, taimekooslused, bioloogiline mitmekesisus, keskkonnategurid, Euroopa, seminatural communities, plant communities, biodivergents, environmental factors, Europe