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Mires of Tierra del Fuego

Mires of Tierra del Fuego. With contributions of: Erwin Adema (RUG) Hans Joosten (Uni-Greifswald) John Couwenberg (Uni-Greifswald) Christiaan Fritz (Uni-Greifswald) Olivier Ogliati (Uni-Greifs.;fotos) Jan Sliva (Uni-Munchen; fotos). 1. 2. 3. 4. 5.

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Mires of Tierra del Fuego

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  1. Mires of Tierra del Fuego With contributions of: Erwin Adema (RUG) Hans Joosten (Uni-Greifswald) John Couwenberg (Uni-Greifswald) Christiaan Fritz (Uni-Greifswald) Olivier Ogliati (Uni-Greifs.;fotos) Jan Sliva (Uni-Munchen; fotos) 1 2 3 4 5

  2. Maria Bahety fen (1) Radicell/sedge peat This region practically has no forests and has a high grazing pressure. The precipitation is low and the evaporation rather high. We visited the fen in a very wet condition. Normally it is much dryer. 7m Sphagnum/radicell peat Lake sediments Sand spring 3500 1500 270 980 220 This fen is fed by groundwater with a relatively low EC 230-350. The surface water has very high EC values (900-1500 µS/cm), since it has dissolved many salts from the surface. At 1m depth we measured 3500 µS/cm. Almost dry salty lake

  3. Maria Cristina fen (2)

  4. Maria Cristina fen 170 117 The fen is fed by groundwater with different EC values. It is also fed by surface water from streams and from ditches along the road. The bog, which is only 60 cm, on top of the fen also stores rain water. So this bog development is very recent 240 170 113 170 >230 550 650

  5. Andorra mire (3)

  6. Andorra mire The spring forest is situated on thin peat where much groundwater discharges. Shifting groundwater flows create opportunities for trees at one site, but may drown trees somewhere else. Strong winds can easily put these trees down. The spring forest

  7. This is the best preserved part of the spring mire. Further down a small rivulet from the hill cuts through the peat and at the end causes some erosion Andorra mire 160 75 150 140 35-40 140 The spring fen 75 This is an older erosion gully, which is now almost dry. These structures drained the mire upstream, so a forest vegetation could develop or a bog.

  8. Andorra mire The spring area The original spring mire could have looked like this, showing spring water coming in and proceeding through the fen peat to the river. Such a mire is extremely sensitive to erosion of inflowing surface water. The results of the German students show that the spring fen was later blocked by the bog expansion.

  9. Andorra mire The bog has a small lagg zone and sometimes small rivulets are formed. Both have low values in EC (ca. 40 µS/cm). Only the rivulets that cross the bog have higher values of about 130 µS/cm 7m 130 The bog margin 40 40

  10. RanchoHambre mire (4)

  11. Rancho Hambre mire 340 110 Sphagnum peat 35 100 14 50 radicel/sedge peat Sphagnum/ radicell peat Lake sediments sand This bog complex is mainly fed by rain and surface water. Most of the surface water originates from rivulets from the slope

  12. Moat mires (5)

  13. Moat mires This lake is a local high point of a mire system. Sphagnum magellanicum is dominant here with EC between 60-95. Slightly under the top an Astelia mire is present with higher EC in the pools (125) > 4 m deep A lake on top

  14. Moat mires So Sphagnum magellanicum appears to be dominant at slightly lower EC then Astelia. 60 110 75 125 97 110/135 135 Going down 126 297

  15. Hans Joosten made a boring in this Sphagnum and Astelia pumila vegetation: under the Sphagnum was over 60 cm of Sphagnum peat, while under the Astelia was 60 cm of Astelia peat, followed by Sphagnum peat. Apparently competition between Sphagnum magallanicum and Astelia can be a stable state for hundreds of years. In most situations Astelia is pushing Sphagnum back to the pool EC = 126

  16. Moat mires In many pools algae appear to be dominant. The algae may compete with Sphagnum magellanicum for nutrients and CO2. EC values are always higher in the algae soup. Further research on the competition for CO2 and nutrients would be very interesting (Sphagnum, Astelia and Algae). If the algae win, this could explain the lack of accumulation in the pools (over 50 cm deep).

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