Plant cover recolonization in the Raessaare milled bog SWEstonia

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Plant cover recolonization in the Raessaare
milled bog (SW-Estonia)

• Mati Ilomets
• Laimdota Truus
• Elve Lode
• Institute of Ecology at Tallinn University,
• Estonia

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Some facts about Estonian peatlands

• 1900
• Total area of peatlands ca 1 mil ha and
  paludified areas some 250 000 ha
• 2000
• Drained for forestry ca 310 000 ha
• Drained for agriculture ca 420 000 ha
• Still not drained ca 270 000 ha(mainly bogs), but
  all surrounded by marginal ditches
• Protected some 170 000 ha

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Study site

• Abandoned and forested cranberry plantation with
  area of some 9,5 ha in SW Estonia.
• Under the southwestern margin of the protected
  Raessaare bog (ca 1260 ha)
• Belongs to Sookuninga Nature Reserve

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Protected mires in Estonia
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Study site

• The Nigula Nature Reserve, as the manager of the
  site, made a decision to remove the tree layer
  and close the ditches on the site

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Study site
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Study aims

• Main aim was to describe the starting situation
  and conditions for the futher monitoring
• Our task was to understand more about
  relationships between plant cover stucture and
  habitat conditions
• water level,
• pore water pH and conductivity,
• peat type
• tree canopy

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Study aims

• And to present our opinion about the vegetation
  response to rising up the water level and cutting
  the trees

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Recent history of the site
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1967 - 1969

• 1967 -plantation was established all trees and
  bushes removed
• Mire surface milled and material removed
• September 1968 - surface milled once more, but
  material left
• Ditches cut and dams constructed
• Oxycoccus palustris and O. macrocarpus sets
  planted
• 1969 - O. macrocarpus disappeared

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1968
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1970 - 1972

• 1970 first Sphagnum patches established
• Dense grass cover formed - Calamagrostis
  palustris, Comarum palustre, Menyanthes
  trifoliata, Phragmites australis, several Carex
  species
• 1971 - some Eriophorum vaginatum, Cirsium
  palustre appeared
• Plantation fertilized with P
• 1972 first cranberry crop

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1973

• The site looks like a bog with Calluna vulgaris
  and Sphagnum
• Share of fen species was unimportant
• Young trees and tree seedlings removed
• Cranberry yield ca 1000 - 1500 kg per hectare

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1973
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Later

• The plantation was managed up to end of
  1980-ties, but trees were not cut any more
• Dams started to leak at mid 90-ties
• Tree canopy more dense
• Water table decreased slowly

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2004
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2004
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1968
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1973
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methods

• on 1x1 m2 plots 100 plant cover analyses
• We found
• species composition and coverage
• On 10x10 m2 plots tree layer species composition,
  height, canopy coverage
• Irradiation on surface and field layer
• Depth to water level, pore water pH and
  conductivity
• Annual dynamics of water level in 10 stations on
  three of four fields and in 7 stations outside
  the fields

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Some results
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Species composition
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Ordination - Nonmetric Multidimensional Scaling
(NMS) field layer

• Significant factors
• Peat type bog Sphagnum versus fen Carex peat
• Pore water pH and conductivity
• Tree canopy density

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Multiple Regression Analyses
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Ordination - Nonmetric Multidimensional Scaling
(NMS) moss layer

• Significant factors
• Peat type
• Tree canopy density

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Multiple Regression Analyses
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Indicator species

• By peat type, IVgt33
• Sphagnum peat
• S. magellanicum
• Calluna vulgaris
• Phragmites australis
• Carex peat
• Agrostis canina
• Potentilla palustris
• Viola palustris

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Indicator species

• Water level lt 10 cm
• Carex lasiocarpa
• Carex rostrata
• Carex nigra
• Agrostis stolonifera

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Classification, field layer
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classification
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Conclusions

• Even after 40 years the species structure of
  communities is not stabilized
• More variable is the situation on fen peat than
  on bog peat
• After removing the tree layer the cover of
  Calluna vulgaris, Sphagnum fuscum and S.
  magellanicum should increase
• This means increasing competition between the two
  groups of plants

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Conclusions

• 5. On the bog peat part the rising up the water
  level should give more advantage to Sphagnum and
  to decrease competitional ability of Calluna
  vulgaris
• 6. On the fen peat part the vegetation response
  is more complicated, but in the moss layer the
  cover of species other than Sphagnum should
  decrease

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Merci de votre attention