COLONIZATION OF THE LAND
Lower Plants on Surtsey
First Colonization Around Steamholes
In the beginning, favourable conditions
for lower plants on land were only to be found around steamholes where
emission of cold or hot steam kept pumice and lava rock continually
first mosses on Surtsey, Funaria hygrometrica and Byrum
argenteum, were found under such conditions in 1967, and the following
year a total of six other species were discovered. These first mosses
were found primarily on damp pumice near steam emissions or in crevices
and drains in the lava. At this time nitrogen-binding cyanophyta (Anabaena
variabilis, Nostoc spp.) were also found around steamholes. Anabaena
vaiabilis seemed to grow in close association with the prothallus
of the moss Funaria hygrometrica. Quite a few species of chlorophyta
and diatoms were discovered at approximately the same time in the green
film that formed on the damp pumice. The only lichen that was able to
grow in such steam emission sites was Trapelia coarctata. It
had become widely distributed near the western crater in 1970 and had
undoubtedly arrived there somewhat earlier. It was restricted to rock
and was unable to grow on the loose pumice.
Colonization of the Lava
In 1970 the first indicators of colonization
of the extensive bare lava flows were found. This community needed more
time to develop, and the species grew considerably slower than those
found earlier around the steamholes. In 1970, the lichens Stereocaulon
vesuvianum and Placopsis gelida and the moss Racomitrium
lanuginosum were discovered. The
moss Racomitrium ericoides had been found the previous year.
The lichen Stereocaulon capitellatum and the moss Schistidium
strictum joined this community in 1971. At this point, all the
principal pioneers of new lavas in Iceland had arrived. The extensive
distribution of all these species on the lava fields of Surtsey where
conditions allowed shows that their dispersal to the island must have
been by air currents. In comparison with the first pioneers at the steamholes,
these species were able to grow on bare lava and did not need humidity
from steam emission holes. On the other hand, they needed a considerably
longer time to grow. The three lichen species had the service of the
blue-green nitrogen-binding Nostoc-algae in addition to green
algae. It had also been shown that, by this time, Nostoc muscorum
had already dispersed all over the island by way of its very light endospores,
which are dispersed by air currents.
In the following years, this lava vegetation
progressed well, but it was clear that it developed more rapidly in
humid lava basins than it did on the tops of lava mounds. It also developed
considerably more rapidly in the rough aa lava on the eastern part of
the island than in the smooth pahoehoe lava farther west. Despite a
good start, this pioneer vegetation suffered setbacks because of prevailing
stormy weather and sandstorms on the island. The western crater was
the most sheltered part of the island, and it is in that area that the
lichens developed most rapidly and the moss Racomitrium lanuginosum
quickly formed a more continuous and dense patch. Soon this moss species
dominated all other pioneering species at several sites and formed small
patches of continuous moss cover similar to those found on young lava
flows in southern Iceland. In 1990 the first lichens of the genus Peltigera
had also developed well in the moss patches.
A milestone in the colonization of mosses
and lichens was reached when the gull nesting colony was well on its
way after 1985 and soil formation was progressing. Various soil lichens
colonized the land, i.e. mealy pixie-cup (Cladonia chlorophaea),
many-forked clad (Cladonia furcata), Cladonia rangifera
and brown-grey moss-shingle (Pannaria pezizoides). At this
time, mosses that are usually characteristic of grasslands and peatlands,
such as Sanionia uncinata and golden ragged moss (Brachythecium
salebrosum), were also found in this plant community. In this enriched
soil, Agaricales fungi also developed; for example, the small
Omphalina rustica, which had become widespread in small bald
patches in the gull colony in 1990.
Diversity of Mosses and Lichens
By the year 2003, the growth of 53 species
of mosses on Surtsey had been confirmed, their increase in number having
been very rapid after 1970. A few other species have also been recorded.
Mosses were quicker to colonize Surtsey than were lichens, most likely
due to their ability to utilize the damp pumice around steam emission
sites, among other places, and due to their more rapid growth. Only
one lichen, Trapella coarctata, could compete with them, and
then only on bare lava.
Lichen colonization has been slower on
Surtsey than colonization by mosses. Forty-five different species of
lichens have been collected on Surtsey, but the total number is undoubtedly
higher, as there are samples that have not been identified yet.
All of the first lichens to colonize bare
lava on Surtsey have three constituents; that is, their fungus has both
a green alga and a nitrogen-binding blue-green alga in its service.
Two species that arrived later, Acarospora smaragdula and Xanthoria
candelaria, were especially associated with lava mounds and birds’
roosting sites. At first the latter species was limited to roosting
sites of sea gulls by the cliffs, and it is almost certain that it was
dispersed to the island on the birds’ feet. The growth of this
species is limited to fertile places where birds roost.
The shore lichens that are plentiful on
sea cliffs along Iceland’s coast have not yet been found on Surtsey.
The shores of Surtsey are too exposed for these lichens to become established
Microscopic fungi colonized Surtsey immediately
in places where organic material was available, as on driftwood on the
shores and elsewhere. Such fungi cannot be seen under ordinary circumstances
without optic aids, except as mildew, but if they are isolated from
collected samples and placed in culture they can be observed more accurately.
The spores of most of these fungi are airborne and thus readily dispersed
to new and distant sites.
fungi become visible temporarily with the formation of fruiting bodies;
for example, the bowl-shaped asci of Ascomycetes. Such fungi have been
seen on Surtsey occasionally, on organic material such as bird corpses
or fish remains carried up onto the lava by birds. In 1994, for example,
a very specialized fungus was discovered, whose only essential nutrient
need is keratin; i.e., animal hair, nails, horns and feathers. This
fungus has been given the Icelandic common name of fjaðrasveppur
which means feather fungus (Onygena cervina). It was discovered
on Surtsey in feather remains.
Many of the fungi in the Basidiomycetes
group form hatlike fruiting bodies. The first of the Agaricales (hat
fungi) to be found on Surtsey was a fungus of the Omphalina genus,
a species that forms a symbiotic life form with a green alga, a kind
of lichen. The thallus of this lichen is green and grows on the bare
lava, and the hat grows up out of it. The most apparent fungus on Surtsey
is another fungus that belongs to the same genus but does not form a
symbiotic life form. This fungus is Omphalina rustica, which
grows mostly in spots of bare soil in the breeding area.
a slideshow of lower plants on Surtsey
(author: Hörður Kristinsson-
- last updated