Pim de Klerk Palynology

Development and funtioning of a skua-mound in Svalbard

 

Bird-manured mires are widespread in the Svalbard archipelago. Relatively large mires that profit from guano input lie beneath cliffs containing large seabird colonies (cf. Van der Knaap 1985, 1988a/b). Furthermore, small peat-hillocks are widespread that are used by Arctic skua (Stercorarius parasiticus L.) for resting or surveying of their territories, and which are referred to as skua-hummocks or skua-mounds.

Normally originating as a watch-post at just a higher spot in the area (e.g. stones or whale-bones), the frequent visits of the birds and the subsequent nutrient-input from excrements allows the establishment of peatforming vegetation types. Peat formation is further favoured by the slow decay of organic matter due to the low Arctic temperatures. Gradually increasing heights resulting from this peat accumulation make these spots continuously attractive for skuas, and eventually small peat mounds are formed with maximum heights of ca. 70 cm and diameters of 1-10 m. The shape is convex or somewhat flattened at the top. The strong manure results mostly in a bright-green colour that contrasts greatly to the surrounding brown tundra vegetation. The permafrost surface is normally at a depth of a few decimetres, i.e. clearly above the permafrost level of the surrounding soils.

Skua-mound "SSM" near Colesbukta after excavation of the section for research (Photo: Hans Joosten)

Partly, naming these landscape elements after skua is imprecise, since there are more skua species of which only arctic skua uses such hillocks, whereas on the other hand also other bird species may produce such mounds, e.g. glaucous gull (Larus hyperboreus), great black-backed gull (L. marinus) and herring gull (L. argentatus). Furthermore the designation "hummock" might provide confusion within the context of peat formation since this term is already in use for another characteristic peatland element ("hummocks and hollows"). 

Location of four palaeoecologically analysed skua-mounds on Svalbard

The Skua-mound "SSM" near Colesbukta was recently studied on pollen and macrofossil analyses, in combination with geochemistry. In combination with other investigated Skua-mounds by Van der Knaap 1988a/b) and Van der Knaap & Jankovksa (unpublished) it will be attempted to formally define and describe these particular landscape elements within classification systems of peat, peat formation, and mires.

This research is carried out in close cooperation with Hans Joosten, Dierk Michaelis, and Pim van der Knaap.

 

Relevant literature:

Möller, I. (2000): Pflanzensoziologische und vegetationsökologische Studien in Nordwestspitzbergen. Mitteilungen der Geographischen Gesellschaft in Hamburg 90: 1-202.

Van der Knaap (1988a): Age and stability of bird-manured vegetation on Spitsbergen. Acta Botanica Neerlandica 37: 171-179.

Van der Knaap (1988b): Palynology of two 4500 year old skua-mounds of the Arctic Skua (Stercorarius parasiticus (L.)) in Svalbard. Polar Research 6: 43-57.

Wüthrich, C. (1992): Stofftransporte Meer-Land: Vogelklifftundra und ornithogene Böden. Stuttgarter Geographische Studien 117: 177-192.

Wüthrich, C. (1994): Die biologische Aktivität arktischer Böden mit spezieller Berücksichtigung ornithogen eutrophierter Gebiete (Spitzbergen und Finnmark). Physiogeographica 17: 1-222.

 

 

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