On the pre-settlement history of Icelandic vegetation
|MargrÚt Hallsdˇttir||BŠndasamt÷k ═slands, BŠndaskˇlinn ß Hvanneyri, Rannsˇknastofnun landb˙naarins, Rannsˇknast÷ SkˇgrŠktar rÝkisins, Tilraunast÷ hßskˇlans Ý meinafrŠi, Veiimßlastofnun||1995||ReykjavÝk|
Frß vefstjˇra: Greinina Ý heild sinni er a finna Ý pdf-skjalinu hÚr a ofan
In recent years more emphasis has been on studying palaeovegetation through lake sediments rather than peat sections, as the pollen assemblages preserved in lake sediments are assumed to reflect more regional vegetation than those stored in the peat. In addition the pollen record of the sediments extends further back in time, most often to the very beginning of the history of the vegetation. The longest record discussed in this paper is from northern Iceland and indicates a harsh environment, solifluction and a discontinuous plant cover in the wake of deglaciation. In the Late Preboreal and Early Boreal Chronozones dwarf shrub heath and shrub heath developed, followed by juniper and birch copses. During the Late Boreal and Early Atlantic Chronozones birch woodland had established itself in the more favourable places, when a climatic oscillation occurred and the birch woodland had a setback, but recovered rather soon again and more than 7000 years ago birch covered the lowland areas both in northern and southern Iceland. During the Late Atlantic and Subboreal Chronozones the birch woodland showed a retrogressive succession towards a more open landscape with expanding peatlands and heaths. Pollen percentages indicate that the woodland regenerated several times during the Subatlantic Chronozone, however the PAR values reflect no such regeneration of the woodland. Perhaps some new and more favourable habitats were created for the birch after a period of cool climate and instability during the latter half of the Holocene.
Key words: birch woodland, climatic change, Holocene, Iceland, pollen analysis, vegetation history.
Grˇurfar ß ═slandi fyrir landnßm
Frjˇkorn hafa skrß grˇurfarss÷gu sÝustu ßr■˙sunda Ý mˇ mřranna og Ý setl÷g ß botni st÷uvatna. Sagan er lesin me afer er nefnist frjˇgreining. Framan af var einkum notast vi mˇmřrar, en ß sÝari ßrum hefur vatnaseti fengi auki vŠgi Ý rannsˇknum ß grˇurfarss÷gu vegna ■ess a ■a reynist geyma betur almenna mynd af grˇurfarinu, ß mean mřrarnar endurspegla fremur stabundna s÷gu. Norur ß Skaga nŠr hin ■ekkta saga lengst aftur ea um 10 300 ßr. Ůar var melagrˇur rÝkjandi fyrsta ßr■˙sundi eftir a land var ÷rÝsa. Mˇlendi me vÝi og lyngi tˇk vi ßur en birkikjarr hÚlt innrei sÝna fyrir um 8500 ßrum. ┴ Flateyjardal var mˇlendi fyrr ß fer svo og einir og birki, ■ˇ a lÝkindum hafi aeins einstakar hrÝslur ■rifist ■ar lengi framan af. Ůar sem skˇglendi ˇx var ■a fyrir verulegum skakkaf÷llum er veur kˇlnai sn÷gglega fyrir um 7500 ßrum. Ůa nßi sÚr ■ˇ ß strik ß nřjan leik fyrir r˙mum 7000 ßrum og breiddist hrafara ˙t, t.d. Ý H˙navatnssřslu ■ar sem ■a hafi ekki ßur mynda ■Úttan skˇg. Birkiskˇgurinn var Ý afturf÷r nokkrum ÷ldum eftir a ÷skulagi H5 fÚll, fyrir um 6200 ßrum, bŠi um noran- og sunnanvert landi. Mˇlendi og mřrIendi sˇttu fast ß um lßglendi, en skˇgurinn hefur tr˙lega haldi sÝnum hlut Ý hlÝum og ß holtum. Birkiskˇgurinn virist ■ˇ nß sÚr nokku ß strik ß lßglendinu ßr■˙sundunum fyrir og eftir Kristbur, lÝklega Ý kj÷lfar betri skilyra til ˙tbreislu eftir kuldakafla ß sÝari hluta n˙tÝma.
This paper presents a review of the presettlement vegetation in Iceland and is based on analyses of pollen assemblages preserved in lake sediments and peat. The timespan dealt with includes the greater part of the current interglacial period, or from the time of deglaciation until the arrival of the Norse settlers some 1100 years ago.
Additional information on the pre-settlement vegetation has been obtained through the presence of megafossils in the form of tree stumps and logs. Also macrofossils may be of value, but unfortunately the seeds, fruit and leaf remains, have enjoyed little attention within the Icelandic scientific community and the only macrofossil study so far is that of Annikki Vasari, which she carried out on two lake sediment cores, one from northern and one from southern Iceland as described in Vasari and Vasari (1990).
When reconstructing the prehistoric vegetation scenarios that we often refer to as some steady state thought of as the "natural vegetation" we rely on pollen assemblages, megafossils and macrofossils as mentioned above. In fact the pre-settlement patterns of vegetation appear to have been much more
dynamic than previously imagined, as they were responding to an ever-changing climate and causing continual evolution of the landscape.
In the last fifty years, knowledge of pollen analysis has gradually been increasing in Iceland. By now there are some fifty pollen diagrams available from sites widely distributed around the country (Table 1). Yet, from a glance at the location map (Figure 1) it is clear that there are still large gaps to be covered, for example, in the northwest, northeast and in the fjords of eastern Iceland as well as in the highlands, where there is a lot of work to be done by scientists of the future. The numerous lakes and peatlands preserve the records of past vegetation, all there is to do is to recover them and fill in the gaps in the knowledge. As a whole we may look at this task as a huge puzzle where many of the bits and pieces are still blank or hidden. Therefore the picture of the pre-settlement vegetation I am going to draw is far from being complete.