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Beavers great for dragonflies and damselflies!

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  • Kathy & Dave Biggs
    NO big surprise here, but still interesting. The difference between 4 and 29 species is huge, but maybe just an effect of having running and still water with
    Message 1 of 2 , Oct 29, 2012
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      NO big surprise here, but still interesting. The difference between 4
      and 29 species is huge, but maybe just an effect of having running and
      still water with more sunshine???
      Kathy Biggs


      http://www.welshbeaverproject.org/beavers-are-great-for-dragonflies/

      *Beavers great for dragonflies and damselflies!
      */
      //News / 27th October 201/2
      *
      The effect of the Eurasian Beaver on Dragonflies and Damselflies (Odonat*a)
      by Sara Schloemer, Lutz Dalbeck and Andreé Hamm. Institute of crop
      Science and Resource Conservation (INRES)*.

      Introduct*ion
      As a result of a reintroduction project in 1981 the Eurasian Beaver
      returned to the Hürtgenwald, a large woodland area in the Eifel mountain
      range in the extreme west of Germany. The study looked at the effects of
      the large-scale changes to dragonfly and damselfly communities in the
      narrow, originally wooded, mountain valleys of the northern Eifel are*a.

      Me*thod
      In order to compare beaver ponds with woodland streams representative of
      large areas north of the Alps, but yet not influenced by the beaver, we
      studied the following habitat types:
      1. Natural springs (definite woodland springs)
      2. Streams (natural -- semi-natural in woodland, not influenced by the
      beaver)
      3. Beaver ponds (some 10 -15 years old, up to 2000 m², sunny to
      half-shaded).
      4. Beaver ponds abandoned for 1 to 3 years.

      All areas were searched for dragonflies and damselflies, their larvae
      and exuvia throughout the season in 2011 and 2012.

      In addition chemical and physical parameters such as pH-value,
      temperature, and water speed were measured at all sample sites, and
      makrozoobenthos collected, in order to gather information on the water
      quality in both the presence and absence of the be*aver.

      *Results
      With a total of 29 species, the number of species in beaver ponds is
      markedly higher than in ponds without beavers (4 species). Even in
      abandoned beaver ponds the number of species is higher than in the
      streams (7 species).

      If species typical of the streams are considered, these also profited
      from the influence of the beaver. This is due on the one hand to the
      dams, which are clearly very suitable habitat and on the other to the
      increased exposure to sunlight, even on stretches of running water,
      caused by the beaver's acti*vities.

      C*onclusion
      Despite the relatively short period of time since the return of the
      beaver, and the rather small number of beaver ponds, the ponds already
      now make a remarkable contribution to the conservation and spread of
      rare dragonfly and damselfly species.
      Beavers contribute markedly to nature and species conservation in the
      densely settled countryside of Central Europe. The species should
      therefore be more greatly integrated into plans to implement
      conservation measures and renaturisation of water bodies than it has
      been to date.
      Particularly notable are:
      - The extraordinary combinations of species (boreal alongside
      sub-Mediterranean species)
      - The extremely different habitat requirements of the species
      - The increase in typical stream dragonflies and damselflies in spite of
      damming by the beaver
      - The increase in part of highly endangered*species

      List of Dragonflies and Damselflies associated with beaver modifi*ed
      habitat (the usual habitat these species are found within is shown
      und/erneath):

      Libellu/la depressa
      Still waters, small, sunn/y and bare

      Libellula qua/drimaculata
      Still waters with well developed/vegetation

      Co/rdulia aenea
      Sta/nding waters

      A/nax imperator
      Standing waters, w/ell-vegetated

      Somatoc/hlora metallica
      Standing and slow-/flowing water/s

      Aeshna cyanea
      Preferring small a/nd shaded pon/ds

      Aeshna juncea
      Acidic heath/y lakes and /bogs

      Aeshna mixta
      Still and s/lowflowing waters

      Orth/ethrum coerulescens
      mainly runn/els in boggy areas
      /
      Orthethrum brunneum
      Small streams, preferring scant/ily vegetated sites

      C/ordulegaster boltonii
      Streams, in forests, o/pen moors and heath/s

      Gomphus pulchellus
      All kinds of slow-flowin/g and standing water/s

      Sympetrum striolatum
      Pioneer /of newly create/d ponds

      Sympetrum danae
      Mostly acidic waters, bogs, mo/orland and heathy lak/es

      Leucorrhinia rubicund
      Acidic, oligotrophic lakes, tarns and bogs, also r/ichly vegetated habitat/s

      Leucorrhinia pectoralis
      Less acidic, mesotrophic bogs, forest lakes, /marshy ditches and/ oxbows

      Brachyton pretense
      Ree/dy canals, marshes, /oxbows

      Calopteryx splendens
      Run/ning waters, avo/iding shade

      Calopteryx virgo
      Running water, cl/assic habitat for/est streams

      Coenagrion puella
      Running and standing water, favours the p/resence of aquat/ic vegetation

      Ischnura elegans
      Running /and especially st/anding waters

      Ischnura pu/milio
      Small or tempo/rary ponds

      Platycnemis p/ennipes
      Running and still water

      E/nallagma cyathigerum
      Lestes sponsa
      Any standing water, numerous /at recent sha/llow or acidic sites

      Lestes virens
      /Heath and bog/ lakes with peatmoss

      Lestes viridis
      Standing or slow flowing wa/ter with bordering t/rees and bushes

      Ceriagrion tenellum
      Small streams,/bogs and heathy la/kes with peatmoss

      Pyrrhosoma nymphula
      Well-vegetated standing and running waters

      --

      California Dragonflies www.sonic.net/dragonfly
      Southwest Dragonflies www.southwestdragonflies.net/
      Bigsnest Wildlife Pond www.bigsnestpond.net/
      ----------------------------------------------------------------
      Kathy and Dave Biggs bigsnest@... 707-823-2911
      308 Bloomfield Rd. Sebastopol, CA 95472


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    • Jim Stuart
      It s a combination of factors ... not just increasing available lentic waters and beaver-cleared openings in stream channels. Beaver dams and ponds capture
      Message 2 of 2 , Oct 29, 2012
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        It's a combination of factors ... not just increasing available lentic waters and beaver-cleared openings in stream channels. Beaver dams and ponds capture sediment that in turn supports herbaceous plants like sedges that many odes use as habitat. Beaver ponds, through succession, become sedge marshes and moist-soil meadows.The dams reduce impact of flash floods, hold water in the stream channel longer, and provide a buffer against the effects of drought. You can see the impact throughout the Southwest from beaver removal ... greater channel incision, reduced surface flows, and ultimately loss of surface water and the diversity of aquatic and palustrine microhabitats that odonates need.
        A few of our Southwestern species (especially here in NM) that seem to rely on or benefit from beaver activity in montane areas include a couple of the same holarctic species mentioned in this publication:
        Aeshna palmata
        Sympetrum danae
        Libellula quadrimaculata
        Leucorrhinia borealis
        Somatochlora semicircularis
        Coenagrion resolutum
        Lestes dryas


        Thanks,
        Jim

        James N. Stuart
        Albuquerque, NM
        jnstuart61 AT yahoo.com
        http://flickr.com/photos/stuartwildlife

        "All calculations based on experience elsewhere fail in New Mexico" -- Lew Wallace, New Mexico Territorial Governor, 1878-81


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