Plant Colonization, Succession and Ecosystem Development on Surtsey with Reference to Neighbouring Islands B

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Fes- erence ff 2 , it it was very similar to Poa n grassland of Elliðaey was ffi and , and B. D. Sigurdsson 1 Festuca n colony, high nutrient input) and Heimaey (no 9380 9379 ffi , E. Ólafsson 1 ). We forecast that with continued erosion of Surtsey, loss of ) with a decline in species richness and diversity. Old grasslands , S. H. Magnússon 1 This discussion paper is/has beenPlease under refer review to for the the corresponding journal final Biogeosciences paper (BG). in BG if available. Icelandic Institute of Natural History, Urriðaholtsstræti 6-8, P.O. Box 125,Agricultural 220 University Garðabær, of Iceland, Hvanneyri, 311 Borgarnes, Iceland Festuca, Poa, Leymus ( of the neighbouring islands Elliðaey (pu seabirds, low nutrient input)very contrasted dense sharply. and The species-poor. pu Dominatedthe by seagull grassland developing onhigher Surtsey. The in species Heimaey richness grassland and was diversity, significantly tuca/Agrostis/Ranunculus and had a more even coverhabitats of and dominants ( increasing impactvelop from and persist, seabirds as a on lush, the species old neighbouring poor islands. grassland will de- In the area impactedcover, by species seagulls richness, dense diversity, plant grasslandhigher biomass than swards and in have soil low-impact developed carbon areas,was and which become found plant remained significantly for relatively the barren.the A invertebrate seagull similar fauna. colony di After became increasingly 2000, dominated the by vegetation long-lived, rhizomatous of grasses the oldest part of islands and all theirwere common species dispersed had by established sea,with on Surtsey. but the The after formation first colonizers 1985tion. of bird-dispersal This a became allowed seagull wind-dispersed thehas colony species principal been on to pathway a the establish netmation island after and loss and invertebrate 1990. of communities consequent Since in speciesneighbouring site 2007 permanent islands on (plants ameliora- plots there and the on soil) island. Surtseyof has and revealed nutrients A that on from seabirds, study two through sea of older their to transfer plant land, succession, are major soil drivers for- of development of these ecosystems. Plant colonization and successionbeen on closely followed. Surtsey In volcanicered 2013, island, on a formed total the in of island;tions. 1963, 69 of Surtsey vascular have had these plant more 59 than species twice were had the present been species and discov- of any 39 of had the established comparable neighbouring viable popula- 1 Iceland 2 Received: 31 March 2014 – Accepted: 22Correspondence May to: 2014 B. – Magnússon Published: ([email protected]) 17 June 2014 Published by Copernicus Publications on behalf of the European Geosciences Union. Abstract Plant colonization, succession and ecosystem development on Surtsey with reference to neighbouring islands B. Magnússon Biogeosciences Discuss., 11, 9379–9420, 2014 www.biogeosciences-discuss.net/11/9379/2014/ doi:10.5194/bgd-11-9379-2014 © Author(s) 2014. CC Attribution 3.0 License. 5 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ects and erent de- ff ff the south coast of Ice- 25km and only 7–35 km ff × 9382 9381 and a height of 175 m a.s.l. During the eruption large 2 ect the vegetation and ecosystem structure. ff in size). They are within a small area of 25km 2 In this paper we describe plant colonization of Surtsey starting with the discovery of The Vestmannaeyjar islands are very young on geological and evolutionary The 1963 submarine eruption and birth of Surtsey island o a volcanic eruption thathad reached lasted an from area November of 1963 2.7 km to June 1967, when the island 2.1 Study area Surtsey is in the Vestmannaeyjar0.001–13.4 archipelago km which consists offrom 18 small the islands south (from tem coast with of the Iceland oldest rockvolcanism (Fig. formations has 1). dating remained from These at 40 000and low islands years BP. frequency Jakobsson, During form in 2009). the a the Holocene, Surtsey, Vestmannaeyjar young the system southernmost volcanic (Sigurðsson of sys- the islands, was formed during plots newly established onand old, soil development neighbouring on islands Surtsey. to compare with the vegetation 2 Methods ecosystem development (Magnússon et al.,del 2009; Moral Sigurdsson and and Magnússon, Magnusson,of 2014; 2010; the Leblans largest et seabird al.,2009) colonies which 2014). of greatly the These a North islands Atlantic harbour (Hilmarsson, some 2009; Hansenthe et first al., plant inis 1965, and among report the avegetation, very permanent soil and plot few invertebrate study communities. to Then initiated we comprehensively in present results follow 1990. from This permanent the study simultaneous development of grees of erosion and ecosystemthe development rise give and a fall unique of opportunity oceanicthan islands. to anticipated. The understand From rate its of birth developmenterosion on the Surtsey (Jakobsson island has et has been al., lost faster 2007). halfto of In play its a the area key colonization role due of to in the heavy seed island oceanic dispersal seagulls and have nutrient come transfer from sea to land, essential for recent Surtsey and Heimaey eruptions and their neighbouring islands with di plexes commonly cited in island biogeography (Whittaker et al., 2008). However, the strict protection of theand island Walker, 2009). which The studies has onat minimized Surtsey Mount human are St. comparable interferance Helens to (Svavarsdóttir the volcanoet long-term in al., monitoring Washington, 2005; USA, del following Moral, thearound 2009; eruption the del of world Moral 1980 have and (Dale evokedrecovery Magnússon, interest have 2014). and commenced. More These new recent include studies eruptions which those of erupted of their in Kastatochi ecological 2008 in e (DeGange, the 2010). Aleutian Islands, timescales. Aside from their volcanic origin they have little in common with island com- was initiated (Lindroth et al.,dóttir 1973; and Friðriksson, Walker, 1975; 2009). Jakobsson Only etAnak a al., few 2007; Krakatau volcanic Svavars- islands (1927) have in(1963) recently and emerged, Indonesia, including Motmot Tuluman (1968) Island in2007). (1953) Surtsey Lake is in Wisdom a on New crucial Long Guinea, example Island because Surtsey in of New the Guinea unbroken (Thornton, record of monitoring and excellent opportunities for chronosequencenity studies development of (Bjarnason, 1991; plant Cutler colonization etstudies and al., are 2008; commu- from Cutler, tropical 2010), most and comparable temperate regions. land was a surprise.but the The previous volcanic eruptions originand in Jakobsson, of 2009). the the The system Surtsey Vestmannaeyjar eruption, had1973, islands soon set occurred followed was a by over the new known, 5000 Heimaey focus yr eruption on in ago the (Sigurðsson islands and extensive geological and biological research The frequent volcanic eruptionsregression in (Arnalds, Iceland 2013). cause In regularare more disturbance lost severe and eruptions, and ecosystem existingcommence. new While biota the surfaces and lava flows created; ecosystems around Mt. thereafter, Hekla colonization in the and south of primary Iceland have succession provided 1 Introduction 5 5 20 25 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | s ff Hy- Alca Fes- . The 2 commu- ff ), northern Morus bas- the south coast (Friðriksson and ff ), razorbills ( C and the mean an- ), storm petrels ( ◦ ), gannets ( nus (Jakobsson et al., 2000). communities are the main ffi ff ) that also lie unsheltered in Uria aalge ff 2 Fratercula arctica ce). Waters o ffi ns ( nus pu ffi ffi Armeria maritima Among common species of the cli Pu and ). The seabirds impact the vegetation with 9384 9383 Oceanodroma leucorhoa ) to the northeast and leeward of Heimaey. Erosion ), common guillemots ( Poa pratensis. 2 Cepphus grylle ) and ), manx shearwater ( F. rubra Rissa tridactyla ), Leach’s petrels ( cinalis, Puccinellia distans ≈ ( ffi s have been cut into the lava shield (Jakobsson et al., 2007). Surtsey is ff ) and Bjarnarey (0.32 km Fulmarus glacialis 2 ), kittiwakes ( ) and black guillemots ( Cochlearia o Heimaey has been impacted by human inhabitation and livestock grazing since the The vascular flora of the Vestmannaeyjar islands contains some 160 species and The climate of the Vestmannaeyjar area is mild and oceanic. At the Heimaey weather respect to substrate typeisland and influence (Magnússon of et seagulls on al., vegetation 1996; development on Magnússon the and Magnússon, 2000). The plots are and spread of survivorsstudies (Friðriksson, of 1975, lichen (Kristinsson 2000; and MagnússonFriðriksson, Heiðmarsson, et 1974; 2009) al., and Ingimundardóttir bryophyte et 2009). (Magnússon al., Separate and 2014) colonization were also2.3 conducted. Study in permanent plots Plant succession has beenthe studied first plots in were permanent established. plots The on location of Surtsey the since plots 1990 was chosen when subjectively with Surtsey has been studiedtions by of biologists the annually island since arecular 1964. thoroughly species. During searched This each provides to visit an updatefrom all unbroken survival and por- 1965, and unparalleled colonization when record of of thetions vas- plant of first colonization first plant colonists are was known, found as on are their the probable island, routes of to dispersal, the propagation present. Exact loca- tuca richardsonii are Johnsen, 1967; Friðriksson, 1975). 9th century. The largergrazed surrounding by islands sheep since and early some times of (Eyjólfsson, 2009). the2.2 smaller have also Plant been colonization and survival on Surtsey all but few occur onsponding Heimaey. to The their size. other The old mostbeach, diverse islands vegetation heathland, harbour is herb also only slope, found 2–28 dry on Heimaey, species,nities. meadow, which seabird corre- On has grassland the and other coastal islands cli vegetation lush types. seabird The grasslands and dominants cli of the grasslands are the rhizomatous grasses are particularly abundanthome (Hilmarsson, to 2009). large Thefulmars breeding ( Vestmannaeyjar populations islands of aredrobates Atlantic pelagicus the pu sanus torda their nutrient transfer fromA sea few to species land, of(Hilmarsson, burrowing, 2009). heathland nest birds building also and breed other on activities. the islands but their density is low the open ocean (Fig. 1). station, the mean annual temperaturenual during precipitation 1963–2012 1599 mm was (Icelandic 5.1 Meteorologicalof O Iceland are productive and rich in marine life (Astthorsson et al., 2007) and seabirds The spit is flooded by surftoll in of extreme the winter storms. island Coastalmost and erosion extensive by has erosion 2012 taken a it has heavy high had occurred seacli been on reduced the by southernstill half, and the to south-western an second part area(0.46 largest km of where island 1.3 km afterwill Heimaey. probably Following leave Surtsey Surtsey to resemble inglasker, the Súlnasker, unprotected Geldungur size neighbouring and are islands Hellisey of (0.02–0.13 Elliðaey km Geirfu- cones were gradually transformed intoThe denser southern palagonite part tu of Surtsey consiststion of the lava rough flows from lava the wasthe craters. gradually Following south-easternmost filled the part erup- in of by thepart drifting island tephra where is airborne from a dust the low has craters, settled. spit except The for formed northern by eroded coastal sediments deposited on the leeward site. tephra cones were formed in explosive phases of the two main central craters. The 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | L. N analyzeer / 10cm depth) were × 1 m soil depth in a small n burrows was counted in > ffi ), great black-backed gull ( slobe (one plot) and north or ff circular plot with a centre in the 2 C to constant oven dry weight. ◦ slopes with ff ). Nesting density was estimated accord- Larus fuscus 9386 9385 ) breed in substantial numbers upon the island. ) have also been encountered in the surveys and 10m area adjacent to each permanent plot. Four × 10m in size, and were sampled with line-transects × Fratercula arctica L. argenteus ns ( ffi Fulmarus glacialis 1 m on a south facing palagonite tu n colonies with high nutrient inputs from sea to land (Table 1), where ffi > 4m randomly placed subplots within or by each permanent vegetation plot. × ) and herring gull ( Plant biomass was harvested on the Surtsey plots every fourth year, since 1999 Soil was sampled within the Surtsey plots in 1998 and again in 2008 (Magnússon A few fulmar nests ( they were included (Magnússon etbreeding al., colonies of 2009). pu The plotsing on to Elliðaey methods were of within Hansenfour dense 4m et al. (2011). TheAverage burrow number occupancy of pu rate ofcommunication, 2013) 66 % was used for to Elliðaey calculate in nesting 2013 density. (E. S. Hansen, personal Since 2003 density ofSurtsey seabird nests has (mainly been seagulls)middle determined around of the annually. a permanent A permanent plots plot 1000son m on was counted. inspected The and nest lesser bowlsmarinus black-backed occupied gull in ( the current sea- (Magnússon et al., 2009),structive the and last carried sampling out occurringsamples in in were a 2011. harvested 10m The at random sampling coordinates,a was the long de- vegetation a was 2 cut m at line,tion ground using was level electric collected. grass The clippers samples with were a dried 7.5 at or 60 2.5 9.5 cm wide cut. Density All of vegeta- seabird nests et al. (2009). Soildepth samples in of three plots locationspowder in per and total Elliðaey plot. C and The and(Carlo N samples Heimaey analysed were were Erba by sieved dry sampled Instruments, through combustion toSurtsey with Italy) 2 10 2008 an mm, cm at NC2100 and ground C Elliðaey Univ. to and of Heimaey in Antwerp, 2013 Belgium. is dealt Only with the here. C data from Keldnaholti), ICETEC, Reykjavik, Iceland. Details are further described in Magnússon were sieved through aand 2 mm nitrogen mesh (N), for carried determination of out pH, by total the organic Centre carbon of (C) Chemical Analyses (Efnagreiningar (Magnússon et al., 2009). Five3, parallel 5, 10 m 7 transects and were 9all laid m vascular across from each plants their plot, were edge. attotal recorded Plant 1, separately cover cover was of for determined each mossesby by meter and the line-intercept along lichens. lines method, the Additional were line, also species as recorded within well and the given as plots the lowestet not possible al., intercepted intercept 2009). value In of thetaken 1 latter cm. sampling, in four each random plot samples (7cm and dia mixed for a composite sample. In the laboratory the samples expected to be impactedplots by (Table 1). high nutrient input from the seabirds2.4 as are Vegetation, the soil Elliðaey and plant biomass The permanent plots are 10m set up within pu soil depth was south facing lava cinder(Sigurðsson crater and slopes Jakobsson, (three 2009).west plots) Similarly, (two) dated four and from north plots (two) 5000–6000 wereenclosed years facing set valley palagonite ago tu up on the onvalley southern Heimaey, was on part created also of dates theout from to island 5000–6000 the years (Fig. ocean ago. 1). it Since The has the probably eruption valley never is in been not a which open seabird the breeding site and thus it was not lished due to loss2012 to there erosion were or 25 revisiontended of plots to methods operational two (see on of Magnússon(Fig. Surtsey the et 1). (Fig. older al., Permanent 2). volcanic 2009). plots, In islandsland In identical 2013 and of to the sampled the the in study Surtsey archipelago, the Elliðaey was plots, same and were ex- way established Heimaey in on the each middle is- of July. The four Elliðaey plots were sampled in alternate years. A few plots have been abandoned and new ones estab- 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1) + ), dis- ), colo- ). During Cakile arctica cinalis, Stellaria media, ffi Rumex acetosella ord, 2006). One way ANOVA and ) and wind-dispersed species ff cinalis ffi Cochlearia o ). Several years into this period, there was 9388 9387 Cochlearia o Cerastium fontanum ) first found in 2011. The total number of plants that have erent taxa. Most of the pitfall trapping was conducted in the perma- ) also colonized the island (Fig. 4). Most of the species were able ff Botrychium lunaria Cystopteris fragilis Sagina procumbens, Matricaria maritima,Poa pratensis, Cerastium P. fontanum, annua, Festuca Ranunculus richardsonii, acris pioneers. Only two ofnizing the during species this ( period,1986–2007, gained roothold a and second established. waveproved In of greatly. This the plant was third triggered colonization period, bythe the approx. occurred southern establishment and part of of a survival the seagull island. of breedingbecame The colony the plants colony, on which locus soon im- of grew to plantof 200–300 colonization. the breeding soil The pairs, and gulls but not alsomands only acted as now improved agents the started of nutrient seed to dispersal. status flourish Plants and with higher expand nutrient (e.g. de- Cakile arctica, Leymus arenarius,this Honckenya period peploides, the Mertensia first maritima ( bird-dispersed ( to survive on the1975–1985, pristine colonization island slowed and and startthan previously survival propagation. (Fig. In of 3). the newcomers They second were was period, less considerably well approx. lower adapted to the harsh conditions than the moonwort ( established on the island at59 any time of is these 69 were species.tions found In the (Appendix (Fig. 2013 3), A), expedition but defined toleast only the as five island 39 locations. a The species plant population colonization appeared thatbe curve to for divided has the have into expanded island viable four over or popula- main thethe first which periods 50 first (Fig. occurs years decade. can 3). in These The at weresal initial mainly invasion and of shore establishing plants plants occurred (Fig. on during 4) the resulting infertile from and ocean disper- sandy volcanic substrate of the island (e.g. 3.1 Plant colonization on Surtsey The first species topersed colonize to Surtsey the in island 1965 by was sea the currents. sea The most rocket recent ( colonizer was a wind dispersed 3 Results on log-transformed values was usedoutside to and determine inside significance of theThe parameters variables gull for were colony plots seabird nesting onsity, density, plant Surtsey plant biomass, cover, (JMP species soil 6.0Acari/Collembola richness, carbon, catches. package; plant invertebrate The diver- SAS same species Inst.,of test richness, 2006). the was and used TWINSPAN invertebrate to vegetationplant and compare biomass classes: these and plant soil characteristics carbon. cover, species richness, plant diversity, (TWINSPAN; classification, Hill, 1979a,prior b). to The analysis. covercation In data cut the was levels transformed ordination were (log The rare set Shannon species to index were 0, ofyses 0.05, species downweighted. were diversity 0.1, In conducted was 0.2, the with calculated 0.5, PC-ORD for classifi- 1.0 6 all (McCune and plots. and Multivariate 1.5 Me anal- after data inspection. nent vegetation plots to relatesuccession the directly. invertebrate In communities this to paper, the wethe vegetation used permanent and data plots plant of on invertebrate Surtsey catches from in 2002 pitfall to traps 2008 in (Ólafsson2.7 and Ingimarsdóttir, 2009). Data analysis Vegetation data (vascular plants only)sey) sampled and in the 2013dence permanent (Heimaey plots analysis in and (DCA; 2012 (Surt- Elliðaey) indirect was ordination) analysed and with two-way detrended indicator species correspon- analysis Invertebrate studies started on Surtsey inSampling 1965 and was were sporadic continued annually from untilan 1984. 1985 integral part to of 2002 thedirect after biological picking which studies. for Sampling di it included recommenced pitfall trapping, and netting became and 2.6 Invertebrates on Surtsey 5 5 25 20 10 15 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | . 2 − ) to Ara- Cochlearia P. pratensis (Table 2). The 2 and spp., − s on the southern ff had a mean cover , which occurred in Honckenya peploides, Leontodon autumnalis, Salix had gained the highest mean L. arenarius H. peploides . had also increased considerably. spp., Poa pratensis, Festuca richardsonii, Cerastium fontanum F. richardsonii and 9390 9389 Taraxacum C. fontanum and Silene uniflora ered a net loss of plant species. Only one new , both of which established late but had reached ff and and P.pratensis . Silene uniflora had lost ground in 2012 and was only found in half of the plots it L. arenarius 5 % cover. The cover was highest in the two plots with well de- and < cinalis Poa annua ffi . Within the colony, there was an average of 221 g dwt m and ects of seagulls on development on Surtsey ff cinalis The invertebrate communities determined from the pitfall traps in the gull colony dur- In 2011, mean plant biomass in plots outside the gull colony was 47 g dwt m There was a great variation in the development of the plant cover, species richness In 2012 there were 22 plant species recorded within the 25 permanent plots (Ap- ffi were dominant in the catches of the pitfall traps were treated separately and joined into peak biomass was in(plots plots 1, with 3 dense and grassaverage 4). total swards Topsoil carbon of in of the 0.05 %, permanent but plots 1.84 % outside inside the theing gull 2002–2006 colony were colony (Table richer 2). in in species 2008For and had the density than invertebrate were the groupsspecies barren that areas found (Table were 2). on identified the average toplots within the outside the species the gull level, colony colonyever there plots, (Table similar 2). in while were the Total only 28.3 two catches half areas per (Table of 2). that day Mites (Acari) in for and the these springtails (Collembola), groups which were how- versity (Shannon) in plotswithin outside the the colony seabird (Table 2). colony in 2012 was 0.5Biomass but was 1.0 highest in in plots H. the peploides northern spit plots, 29 and 30, which had dense cover of 90.3 % (Table 2). Intion occurred. four Average of species richness theThe of plots most colony common the plots species was canopy of 7.7Cerastium the had (range gull fontanum, closed colony 7–12) Honckenya were in and peploides, 2012. Matricaria layering Leymus of maritima, arenarius, Puccinellis vegeta- Sagina distans,o procumbens, Stellaria media, Taraxacum cover of 33.3 % and 16.9cover % respectively. within Six other the species seabird had reached colony over in 1 % 2012 mean (data not shown). Average plant species di- plots outside the gullHonckenya colony was peploides, 4.4 Sagina (range procumbens, 1–9).Arabidopsis Leymus The petraea, arenarius, most Poa common Cerastium annua speciesof fontanum, of 5.0 % were and wascolony the (data only not shown). species In which the had plots reached within over the 1 gull % colony cover the outside average plant the cover gull was veloped shore community on the northern spit (Fig. 2). Average species richness of plant cover of plots outsideof the the seabird plots colony in had 2012 was 7.1 % (Table 2;), but most a spreading phase. Cochlearia o was recorded in in 2008 (Fig.lava 5). within Its the main seabird distribution was colony near where the grass cli swards and competitionand was diversity increasing. in theand permanent carbon plots status in 2012. ofwere This soil absent was (Table or reflected 2), their in from impact the earlier low, plant the sampling. biomass vegetation Where remained breeding poorly seabirds developed. Average 0.01 (Table 2). pendix A). SpeciesSagina with procumbens, the Leymus highest arenarius over relative 50 % frequency of the were bidopsis plots petraea (Fig. 5). The most notable changes were the increases of colonizer was recorded but all the lost species were3.2 very rare. E During 2003–2012 gull nestsnine were within encountered the in main19–50. ten The breeding of average area number the of (Table permanent nestsarea. 2). in study In The the plots plots, ten total outside year number period it was of only 3.9 one nests within nest the varied breeding was from ever encountered, leading to an average of lioration brought about by thespecies gulls with opened limited a seed reserves windowherbacea, for (e.g. S. light-seeded (or phylicifolia, sporophytic) S.establish. lantana, In Platanthera 2007 hyperborea, thelast Botrychium number period, of lunaria 2008–2013, species Surtsey on su the island peaked at 64 (Fig. 3). In the a pronounced increase in colonization of wind dispersed species (Fig. 4). The soil ame- 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | as and (18.4 %) and Anthoxantum in the Surtsey 0.3 % average 2 < F. richardsonii F. richardsonii erence between the Festuca richardsonii ff and erent from the Elliðaey ff Poa pratensis (11.5 %) and n grassland consisted of only three in the sandy plots, but the lava plots ffi ns in the plots of Elliðaey was very high, ffi was the characteristic species of this group 9392 9391 Ranunculus acris L. arenarius (67.2 %), followed by and H. peploides (16.3 %), (4.7 %) which was found on the excavated soil around the P. distans, S. procumbens, P. pratensis , which compares to 5.1 gull nests per 1000 m 2 P.pratensis erences were significant (Table 3). The dominant species in the ff Festuca richardsonii Stellaria media (8.2 %). Agrostis capillaris erences (Table 3). The Heimaey grassland (group I), which lacks seabirds, had ff lands n burrows. Three Surtsey plots of this group had a similar species composition to er significantly (Table 3). C concentration of the soil was considerably lower than in ffi In the fourth Twinspan-group were Surtsey plots which were located outside the gull DCA separated plots with dense grasslands, regardless of location, from poorly de- The third Twinspan-group consisted of Surtsey plots from within or near the gull The dense seabird grassland of Elliðaey and Surtsey (group II) was highest in plant The gradual increase and expansion of dense vegetation of the gull colony has been ff axis was between sandy and lava plots on Surtsey (Fig. 8). The Heimaey plots formed colony and in an earlypoorly or developed, static species succession richness (Fig.(Table 7). and 3). The These diversity plant plots low cover were and of alland the these on 32 plots soil sand/tephra on was substrate, block was with lava verywith (Fig. the poor 2). exception an of in average plots C cover 31 cover. of 6.7 %. All other species ofveloped this and group barren had Surtsey plots on the first axis. Main separation along the second plots of groups Igroup and IV, and II, the butplots di it in group was III elevated were fromwere more the variable plots with ofthe most the common Surtsey species barrens (data not in shown). pu the Elliðaey grassland andP. a pratensis. relatively high or developing cover of colony (Fig. 7). Theland. vegetation The of nesting these density plots wascover lower was was than in in slightly transition the lower, from Surtsey speciesdi plots barrens richness of to and group grass- diversity II, a average plant little higher, but they did not 269 nests per 1000 m plots of the same groupspecies, (Table 3). recorded The Elliðaey in pu allthe plots sward and was inthe significant annual quantity. The predominant species of of group II (Table 3). Nesting density of pu cover but had lowhighest species in richness this and diversity. group The (Table average 3). C On content the of average soil six was species were found in the plots and Surtsey seabird plotslarger (groups II species and richness III;relatively and Table 3). rich diversity. The The in Heimaey grassland top(Table carbon 3). had 10 and In cm far the similar soil speciesin to of rich each the the Heimaey plot grassland Elliðaey Heimaey (Table there(20.8 and 3). plots %), was The Surtsey was an dominant average seabird ofodoratum species grasslands 18 in species the cover were Multivariate classification andyoung, ordination developing vegetation was of usedand Surtsey Elliðaey islands to in sampled 2012 in analyse 2013. toA Four resemblance groups the comparison were older of formed of by grasslands TWINSPAN the the (Fig.sity of 7). di groups Heimaey showed theira floristic, moderate vascular soils plant and cover, density but it of was seabird not den- significantly di The first signs ofthree vegetation were years after visible the on first anarea. nesting aerial By of photo 1998 the it from gulls. had 1988,over At 9 increased approximately that % to of time 6.6 the the ha island area and (Fig. was in 6). only 2012 0.03 the3.3 ha area in had reached Comparsion 12.1 ha of or vegetation development on Surtsey with neighbouring is- number of these animalstwo there areas. In was plots a outsidewhich the fivefold compares gull and to colony significant 108.4 the animals average di per catch day was within 20.3 the animals colony. monitored per day using aerial photographs and satellite images taken regularly of the island. one group (Table 2). They were however not identified to a species level. In the sheer 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | er- ff Pucinellia and grassland under grassland under Sagina procubens P. pratensis/L. arenarius F. richardsonii/P.pratensis 9394 9393 swards were also here (Figs. 9 and 10). Furthest which develop into ), both annuals, did not gain a roothold on the island following their Atriplex H. peploides, F. richardsonii/P. pratensis as pioneers, which develop towards and Wind-borne seeds and spores of various plant species must have rained over the The decrease in rate of plant colonizaton and relative stagnation during 1975–1985, Cakile tolerance of barren substrates and they often require site amelioration prior to estab- is more confined toMagnússon shore et areas al., and 2009). dependse.g. Other snowbuntings, more graylag bird on geese and species marine ravensin may food that recent (Götmark, also have years frequented 1982; have (Magnússon the carried et island al., and seed 2009; bred to Petersen, 2009). Surtsey, island from its birth. Itcrease was, in however, not colonization until of after wind-dispersed species, 1990is a that attributable trend we to that saw the still a improved persists. considerable1985. soil This in- conditions High-dispersal change on wind the borne island species following the are gull known invasion to in have limited reserves and low The presence of seedsand Martin in Herrero, their 2009; diets Calvino-Cancela,breeding is 2011). on Of reported Surtsey, the for it threethat many is large have been species seagull probably the species (Calvino-Cancela the mainto agents lesser visit of black-backed and seed gull dispersal feed on in and Surtsey. inland the Both areas species herring of are gull known the mainland, whereas the great black-backed gull of the new plant speciesthe were seeds found were within to or a at largeditions extent the dispersed from edges to of the the the island birds by colony, had indicatingto the brought gulls that establish and about and that spread the nutrient on ad- necessarypetition the soil from island. established amelioration plants Occurrence for inhibit at the establishment theby of plants margins new gulls arrivals. suggested and Dispersal that other of com- seeds birdsEllis, to 2005; islands Abe, is 2006; reportedtic Aoyama in feeders et several that al., studies use 2012). (Nogales a Most et variety al., gulls of 2001; are foods omnivorous, including opportunis- earthworms, berries and cereal grain. first colonization (Magnússon et al., 2009). was probably caused by poorspecies. soil The conditions invasion and of limitedwas the followed influx by seagulls of a and seeds second formation of wave of new of plant plants their invasion continuing breeding for colony the in next 20 1985 years. Most ( the sea have not been found on Surtsey after 1977 (Fig. 4). However two of the species vealed, show how thevelopment main on vectors the island. of Of immigration75 the % change 69 have during plant been species the dispersed found byyears ecosystem on birds, shore the de- 15 plants island % since by dispersed wind 1965, byplants about and the had 10 sea % relatively by were large the the seeds,ent sea. main rich poor, During pioneers sandy in the substrates. on reserves, first In the enablingnearby the them island. islands case to These and of establish the Surtsey on mainland thefloating nutri- seeds distance is ending from only upon the a the source shores few on of to the Surtsey tens were of high. kilometers New species so dispersed the by chances of 4 Discussion 4.1 Plant colonization on Surtsey The record of plant colonization of Surtsey and the probable routes of dispersal re- with mainly the impact of seabirdsand and 4 increased (Fig. 9). nutrient Atdistans inputs, the as top shown were barren inincreased lava Surtsey nutrient plots plots with inputs. 1, Theunder 3 ordination the showed influence that of the asmore seabirds, the similar the in succession vegetation composition of progressed, than the at sand the and pioneer lava stages areas (Fig. became 8). ence in vegetation composition fromwere the also Elliðaey in and a dense Surtsey cluster,developed plots. as The expected, Elliðaey but Surtsey plots lavato plots the (6 and right 7) and with atcolony the and the best with top poorly of developed the vegetation (Fig. diagram 8). were On Surtsey the plots right that was a were cluster outside of the plots gull a dense and distinct cluster of points on the left of the diagram, underlining the di 5 5 25 20 10 15 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) . A new study 1 − Platanthera hyperborea ects on the vegetation and ff ), an orchid ( Salix ects on plant populations, invertebrates and ff 9396 9395 ) which either grow in association with or require , while the background atmospheric N deposition is 1 − (Leblans et al., 2014). The nutrient enrichment of soil from the 1 − Botrychium lunaria ects of seagulls on development on Surtsey ff The invertebrate fauna of areas outside the gull colony was characterized by low In areas of the island outside the gull colony the plant succession and soil devel- The halt in colonization of new species and a net loss of species on Surtsey after marsdóttir, 2009). Within the gull colony the invertebrate fauna showed a considerable (sensu Grime et al., 1988)the that gulls initially leading responded to to an thetion abrupt increased (Magnússon increase nutrient et in inputs al., species from lost 2009). richness and ground With diversity further to of development more thehave these competitive, vegeta- become species dominant rhizomatous have in grass however thein species vegetation species in of richness the greater and oldest longevity diversity part has that of occurred the during gull this colony. Aspecies development. decline richness andcaught, catches however most of of animals. them derived Dipterans from were the the gull colony majority area of (Ólafsson and species Ingi- opment has remained slow (Magnússon(Stefánsdóttir et et al., al., 2009). 2014) Aarea but gradual (del rates buildup Moral has of and occurred Magnússon, changeof 2014; are vegetation Leblans in not et permanent al., comparable plots 2014). to on The the Surtsey longterm showed gull monitoring that colony it was mainly ruderal species of the soil development onwithin the the island colony however indicates isonly that 47 ca the kg N 1.2 average ha kg annual N ha seagulls input on Surtsey has hadlandbird cascading colonization e on thedóttir, island 2009; Petersen, (Magnússon 2009), et similarRozzell, al., to 2005; the 2009; lupins Ólafsson del on andpatterns Moral, Mount were Ingimars- St. 2009; extended Helens in del (del the Moral Moral present and study. and Magnússon, 2014). These observed a relatively high content ofKenworthy, 1979; nitrogen, Bancroft phosphorus, et potassium al., andcession 2005), minerals (Walker which (Sobey and are and del of great Moral,we importance 2003). estimated in In from primary an nesting suc- earliernutrient density account inputs and (Magnússon from et other gulls al., in studies 2009) the (Hahn Surtsey et colony al., were 2007) about that 25 kg annual N ha portance for the soil enrichment and vegetation development are the faeces that have deposit faeces and regurgitate pellets,ground, fish feathers and marine are invertebrates shed are and spilled corpses on the of birds that die decompose. Of greatest im- of the islands, explicable byand its the larger absence size, of greater sheep habitatof grazing. diversity, open Many more shores, of open sands the swards and plants tephra confined plains to that Surtsey no4.2 are longer species occur on E the older islands. This study shows that thesoil seagulls development. have This had was pronounced also e reflectedjumpstarted in the the invertebrate ecosystem fauna. buildup The birds (Sekercioglu, have 2006). thus At the nesting sites the birds and that most ofof Surtsey the with likely the colonists otherand have outer Johnsen, islands already 1967) of arrived. the showsislands A Vestmannaeyjar that archipelago have comparison (Friðriksson in been of dispersed the theformed and 50 viable years established flora populations all on (Appendix Surtsey the A). The and common flora that species of most Surtsey of is of the by them far other have the richest of any early years. The shifting pattern ofthe dispersal first routes and 50 years their relative ofsal importance colonization spectra during obtained on from Surtsey otherThornton, has volcanic 1996), some islands, Anak e.g. similarities Krakatau, Krakatau to (Partomihardjo(Harrison (Whittaker et the et et al., plant al., al., 1992) disper- 1992; and 2001; Longat Thornton Island the et volcano early al., stages 2001). but They animal- show and wind-dispersal importance patterns of2007 are sea-dispersal may more indicate variable. that competition is increasing in the community with denser swards after 1990 areand three a species small of fernmychorrhizal ( willows fungi ( for germination andChadde establishment and (Schmid Kudray, 2001; and Thornton, Oberwinkler, 1994; 1996;lishment Eyjólfsdóttir, of 2009). these Hence, the species late may estab- partly have been caused by a lack of the fungi in the lishment (Wood and del Moral, 1987). Among the wind-borne species entering Surtsey 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ), ) became grassland n colonies had ffi Anthus pratensis Festuca rubra nity with the plots sampled ffi Plectophenax nivalis 5000 yr old) gives an insight into > as dominant species. The high breeding ) and the meadow pipit ( 9398 9397 Poa pratensis Motacilla alba and ns indicated that nutrient input from the seabirds on Elliðaey was ffi n colonies on Elliðaey, which were also very species poor, of low diversity and ffi erent time scale. ff erent conditions and plant communities of the islands (Friðriksson and Johnsen, ff Festuca richardsonii All the outer islands of the Vestmannaeyjar islands are impacted by seabirds and re- K limitations, a substantial decline in species richness occurred. The trends observed comparison to the Elliðaey/Surtsey seabirdand grassland. the A impact study of ofhas vegetation, demonstrated introduced seabirds that foxes at on highinated seabird islands densities (Croll in plant et the communites are al.,abundance sub-arctic graminoid of 2005). Aleutian dom- grasses archipelago On declined fox-infestedreduced and marine islands the nutrient with vegetation inputs developed reduced (Crollavailability towards et of seabird tundra, al., nitrogen populations 2005). due and Grasslands to phosphorus onversity are (Janssens fertile known et soils to al., with be 1998). high In speciesin their poor central experimental with Europe, study Pavlu low of et plant a al. di- (2012), found that at high doses of N and under no P and fin colonies of Elliðaey than1967; the Friðriksson Heimaey et al., grassland 1972). studied Ourby (Friðriksson results and far showed Johnsen, that the the richest Elliðaeynication, pu soils 2014). in The Heimaey carbon,nutrient grassland as sampled, input well which from as has seabirds, developed nitrogen had, under (N. limited by Leblans, contrast, personal high commu- species richness and diversity in 1967; Friðriksson et al.,developed grassland 1972), plots they on do Surtseyin the showed provide pu a a strong meaningful a had comparison. The best density of the pu several times higher than in the gull colony on Surtsey. ceive external nutrient inputs. Their vegetation has a greater resemblance with the puf- The vegetation of the older Vestmannaeyjarwhat islands ( will be the outcomesites of sampled long-term on succession Heimaeythe on di Surtsey. and Although Elliðaey the in grassland 2013 are small and do not represent all 4.3 Vegetation development on Surtsey in comparison to neighbouring islands early stages allochthonous inputs orcommunities littoral consisting debris of are heterotrophic important scavenging detrivores sources andand for predators pioneering Thornton, (Edwards 2001; Sikesdant and on Slowik, colonization 2010; by Ingimarsdóttirin autotrophs et the (Hodkinson early al., years et 2013), ondevelopment not al., Surtsey is depen- 2002). (Lindroth followed This et by al., wasever further 1973). it also invertebrate is Plant the colonization characterised colonization case by and andlater relatively vegetation diversification. generalist successional How- species vegetation as stages colonizationon is by a harder specialists di of (New and Thornton, 1992) and occurs passerines, the white wagtail ( also started breeding (Magnússonine et al., species 2009; are Petersen, dependantof 2009). food These on is three insects within passer- fortebrate the raising colonization gull their colony of (Ólafsson young young and volcanic and Ingimarsdóttir, islands their 2009). and main Studies nunataks of source inver- have shown that at the ans, saprophagous dipterans and plantasitic feeding hymenopterans had lepidopterans. also Several species becomecolony, a of but part par- their of main the hosts invertebrate areand community dipteran Ingimarsdóttir, of 2009). and the Colonization lepidopteran gull of larvae somependant and on of aphids the the (Ólafsson developing bird vegetation and speciesten invertebrate on fauna years Surtsey of after was the the de- gull formation colony. In ofthe 1996, the first colony, snowbunting landbird ( to breedthe on dense the vegetation island of (Magnússon the and gull Ólafsson, colony had 2003). extended At to that ca. time 5 ha. After 2000 two other springtails (Collembola) aretion indicative activity of (Swift denser et al., vegetationinvertebrates, 1979). such and These as greater animals staphylinid are decomposi- in beetles an the and important gull linyphiid source spiders food colonyfeeding for which (Ólafsson invertebrates larger were had and colonized abundant Ingimarsdóttir, and 2009). started In to the thrive, such dense as vegetation root plant feeding dipter- change in ecosystem structure and function. The high catches of mites (Acari) and 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (Common Moon- ns and other seabirds will ffi Botrychium lunaria ectivenss of a varied assemblage of seed dis- ff 9400 9399 erent seabird impacts are similar to the findings of these ff The Surtsey Research Society has provided logistic support for the study derstanding ecological reponses toResponses to the the 1980 1980 Eruption eruptionand of Crisafulli, of Mount C. St. Mount M., Helens, Springer, St. edited 3–11, by: Helens, 2005. Dale, in: V. H., Ecological Swanson, F. J., inferential techniques, Plant Ecol., 208, 123–136, 2010. two young lava flows on Mount Hekla, Iceland, J. Veg. 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B., Bakker, J. P., Bekker, R. M., Fillat, F., and Jakobsson, S. P., Magnússon, B., Ólafsson, E., Þorvarðardóttir, G., Gunnarsson, K., Baldurs- Jakobsson, S. P., Gudmundsson, G., and Moore, J. G.: Geological monitoring of Surtsey, Ice- Jakobsson, S. P.: Petrology of recent basalts of the eastern volcanic zone, Iceland, Acta Nat. 5 5 30 25 20 30 15 10 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | influence 9406 9405 Permanent plots on Surtsey (S) in 2012, Elliðaey (E) and Heimaey (H) in 2013, year Plot no.S1,3,4S6–10S22,23 FirstS11–14, sampling 16, 18–21S15, Substrate 17 type 1994, 1995S29,30 1990S31, 32 1994 Sandy sheetE1–4 lava 1995H1–4 1994 Sandy sheet 2005 lava Sheet lava 2008 Sheet lava Seabird 2013 Tephra Low hill 2013 slopes Coastal sand Block lava High Cinder and palagonite hill slopes Palagonite hill slopes High High Low Moderate Low Low Low biogeography, J. Biogeogr., 35, 977–994, 2008. on Mount St. Helens, Ecology, 68, 780–790, 1987. aspects of plant colonization on the Krakatau islands, GeoJournal, 28, 201–211, 1992. ical Reviews, edited by: New, T., Cambridge Univ. Press, 287Colonization pp., of 2007. an island volcano, LongMotmot, Island, in Papua New its Guinea, caldera and an2001. lake, ermergent VII. island, The overview and discussion, J. Biogeogr., 28,Univ. Press, 1389–1408, UK, 422 pp., 2003. Press, 346 pp., 1996. of establishment, substrate type and influence of seabirds. Table 1. Wood, D. M. and del Moral, R.: Mechanisms of early primary succession in subalpine habitats Whittaker, R. J., Triantis, R. J., and Ladle, R. J.: A general dynamic theory of oceanic island Whittaker, R. J., Bush, M. B., Partomihardjo, T., Asquith, N. M., and Richards, K.: Ecological Walker, L. R. and del Moral, R.: Primary Succession and Ecosystem Rehabilitation, Cambridge Thornton, I. W. B., Cook, S., Edwards, J. S., Harrison, R. D., Schipper, C., and Shanahan, M.: Thornton, I.: Island Colonization, The Origin and Development of Island Communities, Ecolog- Thornton, I.: Krakatau, The Destruction and Reassembly of an Island Ecosystem, Harvard Univ. 5 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | b 1.47 a 1.11 a 1.04 b 0.79 c ± ± ± ± 0.001. ANOVA ≤ = = p ∗∗∗ 0.22 a 6.23 0.16 b0.15 9.14 b0.12 1.07 b 0.04 ∗∗∗ ∗∗∗ ∗∗∗ ∗ ∗∗ ∗ ∗∗∗ ∗∗∗ p ± ± ± ± s.e.; : average density P ± 9 = Plots 11–22, 29–32; 13.4 75.6 gull n 1.3 2.9 n.s. 0.55 15.2 a ± ± b 0.2 0.9 0.8 ± ± ± ± 1.19 a 1.90 ± ± ± 0.90 b 0.80 0.84 b0.64 b 0.85 0.54 ± ± ± ± 0.001. ≤ 14. = 0.05. = ), plant cover, species richness and = ∗∗∗ 2 n p 16,14 colony 16.34 a 18.00 12.25 a 6.00 11.55 a 7.13 8.73 b 4.43 ± ± ± gull Inside = ± ANOVA level of significance, a n 0.01; 10.7 108.4 1.12.3 28.3 17.7 23.90.02 221.2 1.84 0.01 3.9 = 0.1 1.0 2.80.5 90.3 7.7 88.42 70.99 ∗∗∗ ∗∗∗ ∗∗∗ ∗∗∗ ≤ ± ± ± ± ± ± p ± ± ± = erent at P ff ∗∗ 9408 9407 14.2 13.9 46.7 Outside colony s.e.; /269 G G ± c 0.05: n.d. ≤ = ∗ 2 c − 0.05; > include Coleoptera, Diptera, Hemiptera, Hymenoptera, Lepidoptera, = ), plant cover, species richness and diversity of vascular plants in I 4 0 69.20 II 7 5.13 IIIIV 8 14 2.51 0 7.56 2 c : average density of gull nests on Surtsey 2003–2013; G seabirds− group plots density % richness diversity % + + − Invertebrate species richness Invertebrate catch/day Acari/Collembola catch/day 20.3 Plant biomass g dw m Soil carbon % 0.05 Plant diversity (Shannon) 0.5 Plant cover %Plant species richness 4.4 7.1 Nests no. 0.01 Surtsey permanent plot data. Average density of gull nests in plots on Surtsey Average density of seabird nests (no./1000 m n nests on Elliðaey in 2013. Means ffi IslandHeimaey Presence of Twinspan No. of Nesting Plant cover Species Plant Soil carbon Surtsey/Elliðaey Surtsey Surtsey p Table 3. level of significance, n.s. diversity of vascular plants,Twinspan groupings; and soil carbon in plots sampled on islands, according to main plots 1, 3, 4,Neuroptera, 6–10, Thysanoptera, 23; Araneae,Acari/Collembola) Gastropoda were not and sampled Oligochaeta. in plots Invertebrates 31 and (including 32, 2012, standing biomass10 of cm vascular of soil plants in2002–2006 (live 2008. sampling and Invertebrate and seasons, dead) Acari/Collembola catch in data data are 2011, pitfall are and traps individuals total averages for carbon caught. the in Means top 2003–2012 (no./1000 m Table 2. of pu Means with same letter are not significantly di Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | • 9410 9409 •••• •••• ••• • • ) denotes species that have been recorded on Surtsey but were • ) ) ) ) ) ) ) ) ) ) • • • • • • • • • • ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• ••••••••••••••••••••••••••••••••••••••••••••••••••• ( •••••••••••• ( •••••••••••••••••( ••••••• ••••••• •••• • • ( 2013 v.p. 2013 p.p. 2012 • • ••( 2013••• v.p. 2013••• p.p. 2012 ••••••••••• • • ••( • •••••••••••••( • •••••••••( • ••••( • ••( • ) 1.3 0.46 0.32 0.25 0.2 0.13 0.1 0.04 0.02 0.01 ) 1.3 0.46 0.32 0.25 0.2 0.13 0.1 0.04 0.02 0.01 2 cinalis 2 ffi Continued. Vascular plants colonizing Surtsey during 1965–2013 and species list for neighbour- Stellaria media Cystopteris fragilis Angelica archangelica Carex maritima Puccinellia distans Matricaria maritima Festuca richardsonii Cerastium fontanum Equisetum arvense Silene uniflora Juncus arcticus Poa pratensis Sagina procumbens Atriplex glabriuscula Rumex acetosella Arabidopsis petraea Armeria maritima Poa annua Agrostis stolonifera Alchemilla vulgaris Epilobium palustre Cakile arctica Leymus arenarius Honkenya peploides Mertensia maritima Cochlearia o Capsella bursa-pastoris Luzula multiflora Taraxacum Rumex acetosa Polygonum aviculare Agrostis capillaris Alopecurus geniculatus Ranunculus acris Deschampsia beringensis Empetrum nigrum Agrostis vinealis Eleocharis quinqueflora Phleum pratense Montia fontana Island size (km Island Surtsey Surtsey Surtsey Elliðaey Bjarnarey Álsey Suðurey Hellisey Brandur Súlnasker Geirfuglasker Þrídrangar Poa glauca Juncus alpinus Salix herbacea Galium normanii Species total 59 39 22 28 28 24 22 9 11 7 4 2 Island size (km IslandPotentilla anserina Anthoxanthum odoratum Leontodon autumnalis Rumex longifolius Polypodium vulgare Luzula spicata Myosotis arvensis SurtseySalix phylicifolia SurtseyOxyria digyna Surtsey Elliðaey Bjarnarey Álsey Suðurey Hellisey Brandur Súlnasker Geirfuglasker Þrídrangar Salix lanata Euphrasia frigida Plantago maritima Platanthera hyperborea Galium verum Plantago lanceolata Thymus praecox Saxifraga caespitosa Rhodiola rosea Festuca vivipara Achillea millefolium Alopecurus pratensis Calamogrostis stricta Gymnocarpium dryopteris Epilobium collinum Botrychium lunaria Ranunculus repens Draba incana Juncus bufonius Epilobium hornemanni Saxifraga rivularis 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 1 2 3 4 5 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 Surtsey order of colonization Neigbour islands additional species Table A1. ing Vestmannaeyjar islands. ( Table A1. not present in 2013;within species permanent that plots had (p.p.)lands formed in is viable 2012 populations based are (v.p.)2010–2013. on marked. in Friðriksson The 2013 species and or list Johnsen, were of found 1967 the and Vestmannaeyjar our is- surveys of Elliðaey and Álsey in

9412 9411

2. Fig.

Location of permanent plots on Surtsey, infra-red Rapid Eye image from 28 Au- Surtsey and other Vestmannaeyjar islands on an infra-red Rapid Eye image from 1. Fig.

Figures.

4 5 6 3 1 2

9 8 5 6 7 3 4 2 1 Figure 1. 28 August 2012. Areas withLocation dense of vegetation vegetation appear plots in sampled red on colour, Elliðaey e.g. and gull Heimaey colony in on 2013 Surtsey. is shown in yellow. Figure 2. gust 2012. Note densemunity vegetation (1 of ha) gull on the colony northern (13 ha) spit. on Plots the 1, 3, southern 4, lava 6–10 and and shore 23 com- are within the gull colony. 10

erent ﬀ 2015 2015 2010 2010 2005 2005

2000 2000 1995 1995

1990 1990 9414 9413 1985 1985 1980 1980 1975 1975 Cumulative 1965 from Cumulative each year Present Sea Birds Wind 1970 1970

1965

0 1965

0 50 40 30 20 10 80 70 60

50 40 species 30 of 20 Number 10 60 Number of species of Number Cumulative curves of dispersal routes to Surtsey most probably used by di Surtsey colonization curve for vascular plants during 1965–2013.

Fig. 4. Fig.

Fig. 3. Fig.

4 5 3 2 1 Figure 4. Figure 3. vascular plant species duringsites 1965–2013. of establishment Based on on the dispersal-mode island. spectra of the ﬂora and

4 5 1 2 3

25 20 15 10 5 0 9416 9415 2012 2 plots are shown. ≥ Poa annuaPoa

Taraxacum Taraxacum Poa pratensis Poa

Silene uniflora Silene Stellaria media Stellaria 2008 Rumex acetosella Rumex Leymus arenariusLeymus Puccinellia distans Puccinellia Sagina procumbens Sagina Festuca richardsonii Festuca Mertensia maritima Mertensia Arabidopsis petraea Arabidopsis Matricaria maritima Matricaria Cerastium fontanum Cerastium Cochlearia officinalis Cochlearia Honckenya peploides Honckenya Fig. 6. Fig.

Fig. 5. Fig.

6 7 4 5 1 2 3

Expansion of dense vegetation within the Surtsey seagull colony during 1988–2012. Relative frequency of vascular species in the 25 permanent plots on Surtsey in 2008 4 3 1 2 Figure 6. Approximation from aerial anderosion sattelite over the images, period. by Anette Th. Meier. Island outlines indicate Figure 5. and 2012. Species occurring in

S18 600 input barrens, - Arabidopsis petraea Rumex acetosella

S19 S30

S12 S20 S29

S15 low N low

S11

S tephra tephra S

S14 S17 S21

input barrens, barrens, S13 -

S lava lava S N low pratensis S31

400 Honckenyapeploides S16 S32 Leymus arenarius Cerastium fontanum Sagina procumbens Poa S23 S10 Axis 1 Axis

S22 S3 9418 9417

S9 S1

S4 S8

E2 nsis S7 E3 input - 200 E1 E4 Stellaria media S6 Festuca richardsonii Poa prate

highN

E & S grassland S & E ,

input -

seabirds, seabirds, H4 grassland

H N low H3 H2 0 H1 0

200 400 TWINSPAN-classiﬁcation of permanent plots sampled on Surtsey (S), Heimaey (H) Axis 2 Axis DCA-ordination results for permanent plots sampled on Surtsey (S), Heimaey (H) and Ranunculus acris Anthoxantum odoratum Galium verum Luzula multiflora

8. Fig

Figure 8. Elliðaey (E) in 2012–2013.inputs Arrows from indicate breeding seagulls. direction of succession on Surtsey under nutrient Figure 7. and Elliðaey (E) inand 2012–2013. the Species four most groups decisive formed. (indicators) of each division are shown 5 4 2 3 1

47 48

grassland on upper parts of Elliðaey. Plot E1 9420 9419 grassland in centre of gull colony (plot 1) on Surtsey

n colony on palagonite slope above and to the right of cottage. Photo: BM, ﬃ

Festuca richardsonii/Poa pratensis Poa pratensis/Leymus arenarius

10. Fig.

Fig 9. Fig

4 5 6 7 3 2 1 4 5 3 2 1 Figure 10. was located in a pu Figure 9. in 2013. Upper crater areas and palagonite ridges remain barren. Photo: BM. 2010.