Antarctic Science 22(6), 691–702 (2010) & Antarctic Science Ltd 2010 doi:10.1017/S0954102010000568 Lichen and moss communities of Botany Bay, Granite Harbour, Ross Sea, Antarctica RODNEY D. SEPPELT1, ROMAN TÜRK2, T.G. ALLAN GREEN3, GERALD MOSER1, STEFAN PANNEWITZ4, LEO G. SANCHO5 and BURKHARD SCHROETER4 1 Australian Antarctic Division, Channel Highway, Kingston, TAS 7050, Australia Universität Salzburg, Fachbereich Organismische Biologie, Hellbrunnerstrasse 34, 5020 Salzburg, Austria 3 Biological Sciences, University of Waikato, Private Bag 3105, Hamilton, New Zealand 4 Botanisches Institut, Universität Kiel, D-24098 Kiel, Germany, and Leibniz Institute for Science and Mathematics Education, University of Kiel, Olshausenstrasse 62, D-24098 Kiel, Germany 5 Dpto. Biologı́a Vegetal II, Facultad de Farmacia, Universidad Complutense, 28040 Madrid, Spain rod.seppelt@aad.gov.au 2 Abstract: Botany Bay is one of the richest sites for lichen and bryophyte biodiversity in continental Antarctica. A total of 29 lichen, nine moss and one liverwort species have been identified. The most extensive vegetation occurs on a sheltered raised beach terrace. Vegetation associations are described and compared to other continental Antarctic localities that also possess a rich vegetation cover. Ordination analysis clearly indicates the importance of the type of water supply, its regularity, the substrate type, and particularly in Botany Bay, the influence of nutrients derived from the local bird population in governing plant distribution and associations. A vegetation map has been produced and can be used as a baseline to assess vegetation changes over time. Received 5 April 2010, accepted 9 May 2010 Key words: biodiversity, climate change, cryptogams, vegetation associations, Victoria Land 1994, Seppelt et al. 1988, 1995, Ling & Seppelt 1998, Seppelt 2002) and more rarely from surveys covering larger areas (Castello & Nimis 1995, Cannone & Seppelt 2008). The vegetation is composed entirely of cryptogams. Algae and cyanobacteria dominate the ephemerally wet basins and stream areas (Howard-Williams & Vincent 1989, HowardWilliams et al. 1989, Vincent et al. 1993, Tang et al. 1997, Vincent 2000). In localities where at least ephemeral moisture is plentiful, bryophytes (mosses and one liverwort Cephaloziella varians) may form extensive patches but generally their occurrence is patchy, while in dryer areas their biomass is often exceedingly low. Lichens are found in a wide variety of habitats, on rock, sand, mosses, weathered feathers and bones, but rarely is cover or biomass very great. They may also occur within rocks as endoliths and, in the Dry Valleys, this is the most common vegetation type over many square kilometres of the valley floors, predominantly on the northern faces of suitable moraine boulder debris and country rock outcrops. Botanical ‘‘hot spots’’ having substantial vegetation cover are known from the Canada Glacier, Taylor Valley and from Botany Bay, Granite Harbour in southern Victoria Land; Edmonson Point in central Victoria Land; Beaufort Island in the Ross Sea; Cape Hallett and Birthday Ridge, northern Victoria Land; and the Windmill Islands, Wilkes Land. The vegetation of continental Antarctic regions is a reflection of the rigours of the cold desert environment where plant distribution is limited primarily by the availability of free water (Kennedy 1993), although in Introduction A detailed knowledge of the composition of the flora and of the principal vegetation communities in continental Antarctica (treated here as the main mass of the continent and excluding the Antarctic Peninsula) is urgently needed as it is realized that the terrestrial ecosystem may provide one of the earliest indicators of global climate change, particularly through the influence of increased temperatures (Petersen & HowardWilliams 2001). Temperatures in some parts of Antarctica are rising, particularly in the maritime Antarctic (Oppenheimer 1998). Around the northern Antarctic Peninsula, temperature rises have led to significant losses in the floating ice shelves and also in significant range extensions southward of the two indigenous flowering plants (Fowbert & Smith 1994, Smith 1994) whilst in other areas temperatures are thought to be falling slowly (Turner 2004, Turner et al. 2005), although Steig et al. (2009) present evidence for a warming trend that is much more widespread than previously acknowledged. Laboratory studies on the soil fauna from the McMurdo Dry Valleys, Ross Sea region, suggest that drastic changes in composition or dominance may occur (Doran et al. 2002). Our knowledge of the vegetation of continental Antarctica is derived predominantly from a small number of studies in the vicinity of major stations in coastal regions (e.g. Filson 1966, 1974, Horikawa & Ando 1967, Kuc 1968–69, Longton 1972, 1973, Seppelt & Ashton 1978, Kappen 1985, Broady 1986, Smith 1988, 1999, Schwarz et al. 1992, Melick et al. 691 692 RODNEY D. SEPPELT et al. some localities such as the Windmill Islands, soil nutrients derived from relict penguin colonies are also important in determining abundance (Beyer et al. 2000a, 2000b). Despite some 60 years of scientific exploration, the vegetation of the McMurdo region, southern Victoria Land (77–808S, 160–1688E), remains relatively poorly understood or documented. The first attempt at a vegetation classification was that of Longton (1973) using a modified version of the classification developed by Gimingham (1967) and Gimingham & Smith (1970) for the maritime Antarctic. Longton recognized eleven plant sociations. The overwhelming impression from this study is one of an impoverished continental Antarctic terrestrial flora. Only three mosses and eight lichen species were named and high cover and biomass were found only in dense moss patches associated with regular meltwater areas. Schwarz et al. (1992) carried out a detailed study of one of the larger bryophyte patches, located at the Canada Glacier flush, Taylor Valley (then Site of Special Scientific Interest SSSI 12, now Antarctic Specially Protected Area ASPA 131). Although biomass was locally high with cover up to 100%, only three mosses Bryum argenteum, B. pseudotriquetrum and Hennediella heimii were found, the last with aborted sporophytes (Seppelt et al. 1992). Two lichen species were subsequently reported growing on the sides of small stones in the melt stream arising from the side of the glacier and draining through the moss flush (Green et al. 1992). Species lists are available for two other sites in the McMurdo Dry Valleys region, namely Kar Plateau (76856'S, 162820'E) (Seppelt et al. 1995, 1996) and Beaufort Island (76857'S, 166855'E) (Seppelt et al. 1999). The north end of Beaufort Island represents an interesting site with a moss bed c. 1 ha in area with nearly 100% cover composed almost entirely of one species, Bryum argenteum, and only a very minor cover of Hennediella heimii. At Cape Hallett (72819'S, 170816'E), northern Victoria Land, a similar situation occurs with extensive vegetation dominated by Bryum argenteum and filamentous green algae occurring on an ephemerally wet beach terrace, where high nutrient input and atmospheric ammonium from penguins and skua gulls may limit diversity. Seppelt & Green (1998) published a bryophyte flora for southern Victoria Land which included seven moss species and the liverwort Cephaloziella varians. All these species can be found at one of the most botanically diverse areas of continental Antarctica - Botany Bay, Granite Harbour (778S, 1628E). The first collections of plants from this region were made by the National Antarctic ‘‘Discovery’’ Expedition 1901–04 (Cardot 1907). The western geological party of the British Antarctic Expedition of 1910–13 was based at Cape Geology, at the northern end of Botany Bay, but no plant collections appear to have been made (Schroeter et al. 1993). We have undertaken extensive fieldwork in the Granite Harbour region over a number of summer seasons, commencing with a preliminary survey in December 1989. Detailed studies on the flora, vegetation, ecology, photosynthetic physiology of mosses and lichens, and floristic and landscape mapping began in 1992 and concluded in January 2008. The Botany Bay–Cape Geology area is now very justifiably designated as Antarctic Specially Protected Area 154, to conserve and protect the unique biological richness of the site. Unless otherwise stated, nomenclature for mosses follows Ochyra et al. (2008). Nomenclature for lichens follows Øvstedal & Lewis Smith (2001). Nomenclature for liverworts follows Bednarek-Ochyra et al. (2000). Study area and methods Site description Botany Bay and Cape Geology are situated in the southwestern corner of Granite Harbour, southern Victoria Land, at 162832'5200 E, 77800'1400 S, c. 100 km north-west of Ross Island. The area consists of raised boulder beach terraces, weathered rocky steppes and irregular rock platforms around Cape Geology, rising rapidly to the south to include a well-defined elevated cirque containing a small ice field. The bedrock geology at Cape Geology has been described as a porphyritic grey biotite-granite, with phenocrysts of orthoclase of reddish colour, casting the weathered rock with a reddish tinge (Antarctic Treaty Secretariat: http:// www.ats.aq/e/ep_protected.htm). The area faces north and is well protected from strong winds. The impact of the sun is also magnified by the sea ice sheet that normally remains in Granite Harbour until about the end of January so that light levels are very high. Sensors in the same plane as the lichens recorded incident PFD (photon flux densities) up to 2800 mmol m-2 s-1, about 40% above normal full sunlight. Cape Geology and Botany Bay, in particular, are much warmer than expected and air temperatures can reach almost 108C with some days in early January being almost frost free (Schroeter et al. 2010). The area is extremely rich botanically for such a highlatitude location - it is also one of the richest sites in the whole of continental Antarctica. There is a high diversity and abundance of lichens (more than 30 species) and mosses (nine species), and the structure and development of these communities are similar to those found 108 of latitude further north. Some lichen thalli (e.g. Umbilicaria aprina) measure up to 15 cm diameter. The boulder beach has rich populations of both epilithic and endolithic lichens. The area is the type locality for the lichens Buellia frigida (Darbishire 1910) and Caloplaca coeruleofrigida (Søchting & Seppelt 2003). The area contains by far the most southerly record of an hepatic, Cephaloziella varians, and the mosses Bryoerythrophyllum recurvirostrum and possibly Ceratodon purpureus (Seppelt & Green 1998). There are abundant growths of algae (at least 85 taxa), although the algal flora is not considered particularly unusual for the locality (Broady 2005). There are large populations of invertebrates (collembola, mites, nematodes, rotifers) and the area is the type locality VEGETATION OF BOTANY BAY 693 Table I. Bryophytes and lichens of the Botany Bay–Cape Geology region, Granite Harbour, Victoria Land, Antarctica. HEPATICAE 1 Cephaloziella varians (Gottsche) Steph. MUSCI Bryoerythrophyllum recurvirostrum (Hedw.) P.C.Chen 2 Bryum argenteum var. muticum Brid. Bryum pseudotriquetrum (Hedw.) P.Gaertn., B.Mey. & Scherb. Ceratodon purpureus (Hedw.) Brid. 3 Didymodon brachyphyllus (Sull.) R.H.Zander Grimmia plagiopodia Hedw. Hennediella heimii (Hedw.) R.H.Zander Schistidium antarctici (Cardot) L.I.Savicz & Smirnova 4 Syntrichia sarconeurum Ochyra & R.H.Zander Fig. 1. Map of inner Granite Harbour showing the location of Botany Bay (162832'52''E, 77800'14''S), and other major named features. Note how Botany Bay is north facing and well protected from winds coming from the ice shelf (to the left) and the polar plateau via the McKay Glacier. for the collembolan Gomphiocephalus hodgsoni. There is a colony of between 40–50 breeding pairs (and numerous nonbreeders) of the south polar skua (Catharacta maccormicki). These numbers are approximately the same as those present in 1911–12 (Taylor 1913, 1916). No other bird species are known to breed in the Cape Geology area, although Adélie penguins occasionally come ashore to moult. Nutrient input from skuas, from meltwater percolating from the ice covered slopes to the west, and occasionally from the sea when the sea ice breaks out, plays a significant part in determining the abundance of the biota, together with water availability from snowmelt and ephemeral melt streams. Ecological survey Relevées were located within the altitudinal range 5–40 m above sea level at three primary locations: Botany Bay, Cape Geology, and the beach terrace near the designated campsite c. 1 km south-west of Cape Geology (Fig. 1). 186 relevées were recorded using either 50 cm x 50 cm or 20 cm x 10 cm quadrats. Species presence was noted and in the larger quadrats, cover estimates were made visually. For the smaller quadrats, cover estimates were obtained using point intercepts at 1 cm intervals with the frame gridded using fine fishing line and the point intercept being that point at which the lines crossed in grid corners. Field estimations of cover values using visual assessment or point quadrats maintained an accuracy of ± 1%. Within relevées lichen substrates were recorded as saxicolous, terricolous or muscicolous. Botany Bay was also mapped in detail using a building level to obtain altitude above sea level and plant distribution mapped using subjective categories which reflected the major plant type or species present. LICHENS Acarospora gwynnii C.W.Dodge & E.D.Rudolph Amandinea petermannii (Hue) Matzer, H.Mayrhof., & Scheid. Buellia frigida Darb. 5 Buellia cf. papillata (Sommerf.) Tuck. 6 Buellia subfrigida Mas. Inoue Caloplaca athallina Darb. Caloplaca citrina (Hoffm.) Th.Fr. Caloplaca coeruleofrigida Søchting & Seppelt Caloplaca cf. schofieldii C.W.Dodge Caloplaca saxicola (Hoffm.) Nordin Candelariella flava (C.W.Dodge & Baker) Castello & Nimis 7 Carbonea vorticosa (Flørke) Hertel Lecanora expectans Darb. Lecanora mons-nivis Darb. Lecidea andersonii Filson Lecidea cancriformis C.W.Dodge & G.E.Baker Lecidella siplei (C.W.Dodge & G.E.Baker) Mas. Inoue 8 Leproloma cacuminum (A.Massal.) J.R.Laundon Physcia caesia (Hoffm.) Fürnr. Physcia dubia (Hoffm.) Lettau Rhizocarpon geminatum Körb. Rhizocarpon geographicum (L.) DC. Rhizoplaca melanophthalma (Ram.) Leuck. & Poelt Rhizoplaca cf. priestleyi C.W.Dodge Sarcogyne privigna (Ach.) A.Massal. Turgidosculum complicatulum (Nyl.) J.Kohlm. & E.Kohlm. Umbilicaria aprina Nyl. 9 Xanthomendoza borealis (R.Sant. & Poelt) Søchting, Kärnefelt & S.Kondratyuk Xanthoria elegans (Link.) Th.Fr. Notes: 1. Cephaloziella varians has previously been referred to as C. exiliflora (fide Bednarek-Ochyra et al. 2000). 2. Bryum argenteum var. muticum has previously been referred to as Bryum subrotundifolium (fide Ochyra et al. 2008). 3. Didymodon brachyphyllus has previously been referred to as Didymodon gelidus (fide Ochyra et al. 2008). 4. Syntrichia sarconeurum has previously been referred to as Sarconeurum glaciale (fide Ochyra et al. 2008). 5. Buellia cf. papillata, growing on moss, has previously been referred to as Buellia grimmiae. 6. Buellia subfrigida has previously been referred to as Aspicilia glacialis (Seppelt et al. 1995) and Hymenelia glacialis (Øvstedal & Lewis Smith 2001). 7. Carbonea vorticosa has previously been referred to as Lecidea blackburnii (Seppelt et al. 1995). 8. Leproloma cacuminum has previously been referred to as Lepraria sp. 9. Xanthomendoxa borealis has previously been referred to as Xanthoria mawsonii (see Lindblom & Søchting (2008). 694 RODNEY D. SEPPELT et al. Table II. Buellia frigida sociation composition. Total average cover Buellia frigida Umbilicaria aprina Xanthoria elegans Candelariella flava Xanthomendoza borealis Rhizoplaca melanophthalma Physcia caesia Caloplaca cf. biatorina Rhizocarpon geminatum Caloplaca coeruleofrigida Buellia cf. subfrigida Rhizocarpon geographicum Lecidea cancriformis % Frequency % Cover 100 77 66 64 50 38.6 26 11 8.6 2.3 2.3 2.3 1.2 54.2 44.9 3.8 4.1 1.32 0.65 0.25 0.43 0.38 0.19 0.08 0.04 0.02 0.01 Data analysis The classification of data from visual estimates and the 186 relevées by ‘‘two-way indicator species analysis’’ was carried out using TWINSPAN 1.0 (Hill 1979) at default settings. This is a dual technique, providing classification of samples and species. Groups of samples are characterized by a characteristic species combination, or at least a group of differential species (Økland 1990). Further ordination analysis was carried out using a detrended correspondence analysis (DCA) (Hill & Gauch 1980) using the program CANOCO 4.0 (ter Braak & Smilauer 1998). Results The terrestrial lichen and moss flora of Botany Bay–Cape Geology comprises one liverwort, nine mosses, and at least 30 lichens (Table I). Several lichen species attributable to Buellia and Lecidella remain as yet undetermined. Cyanobacteria, particularly Nostoc, and green algae, particularly Prasiola crispa, are also abundant in the region. The classification of the vegetation of the Cape Geology– Botany Bay region includes five lichen-dominated sociations Table IV. Umbilicaria aprina–Rhizocarpon geographicum sociation composition. Total average cover Umbilicaria aprina Rhizocarpon geographicum Indeterminate grey crust Rhizocarpon geminatum Physcia caesia Buellia frigida Candelariella flava % Frequency % Cover 83 67 67 33 50 50 16 75.95 20 35 61 3 1 1 2 and two moss dominated sociations within the Crustaceous Lichen and Foliose–Fruticose Lichen subformations and Short Moss Turf and Cushion subformation, with one algal dominated sociation within the Alga subformation (sensu Longton 1979). Because of the co-association of both crustose and foliose lichens over much of the region we have chosen not to adopt the subformation categories of Longton (1979). Consequently, the vegetation is classified at the sociation level. Antarctic nonvascular cryptogam tundra formation 1. Buellia frigida sociation This sociation occurs primarily on granitic boulders on the raised beach terraces, and sheltered sides of massive country rock risers, steppes and terraces. Water availability is primarily derived from snow deposits (the boulders can be almost covered by winter snowfall), by snowmelt from adjacent snow patches or, very occasionally, by summer snowfall. In Botany Bay, the south- and south-west-facing (i.e. towards the cliffs inland) sides of boulders are covered (almost 100%) by crustose lichens while the north- and northeast-facing (i.e. towards the frozen sea) sides are mostly devoid of lichen cover. This effect is so strong that when viewed from the sea ice the boulders in the bay appear to have no lichen cover at all. Nutrients are derived from snowmelt and from direct deposition of guano derived from the local breeding skua gull population. Plant composition in the 70 relevées is summarized in Table II. Table III. Physcia caesia–Buellia subfrigida sociation composition. Total average cover Physcia caesia Buellia cf. subfrigida Rhizocarpon geminatum Umbilicaria aprina Buellia frigida Rhizoplaca melanophthalma Candelariella flava Rhizocarpon geographicum Xanthomendoza borealis Xanthoria elegans Sarcogyne privigna Unidentified algae % Frequency % Cover 92 95 100 89 79 66 42 36 29 13 5 74 60.5 14.7 7.9 10.8 7.6 6.9 0.54 0.28 0.34 0.17 0.20 0.05 10.9 2. Physcia caesia–Buellia subfrigida sociation This sociation is predominant in areas of meltwater flow along ephemeral streams or melt channels and where there is Table V. Xanthomendoza borealis sociation composition. Total average cover Xanthomendoza borealis Xanthoria elegans Prasiola crispa Bryum argenteum Bryum pseudotriquetrum Hennediella heimii % Frequency % Cover 100 30 70 70 30 8 54 38 0.3 0.8 2.07 0.9 0.31 695 VEGETATION OF BOTANY BAY Table VI. Caloplaca citrina sociation composition. Total average cover Caloplaca citrina Lecanora expectans Xanthomendoza borealis Physcia caesia Xanthoria elegans Candelariella flava Caloplaca athallina Physcia dubia Rinodina sp. Nostoc sp. % Frequency % Cover 97 83 33 21 4.8 4.8 4.8 9.5 7.1 9.5 19.3 8.4 4.8 5.7 0.28 0.05 0.08 0.08 0.08 0.07 0.67 regular melt seepage over rock. The two dominant species are largely restricted to these habitats in the region. Physcia caesia and, to a much lesser extent Physcia dubia, often form pronounced lines along streams and channels in such a position that the thalli are regularly covered with water at peak flow each day. Cyanobacteria and chlorophycean algae are often present in these habitats but were not identified in this study. Plant composition in the 38 relevées is summarized in Table III. 3. Umbilicaria aprina–Rhizocarpon geographicum sociation This sociation is found on sheltered, humid and well-watered vertical rock faces or along melt seepage or drainage over stepped ledges and ice fractured country rock. Moisture and shelter appear to be the principal determining ecological parameters. Plant composition in the six relevées is summarized in Table IV. 4. Xanthomendoza borealis sociation This sociation is found primarily on sandy gravels and coarse sandy soils and on rock faces in dryer habitats where there is considerable ornithogenic nutrient input. Often the patches of gravel and sand are found in shallow depressions, on ledges and on level areas of country rock where snow and meltwater collect. Plant composition in the 13 relevées is summarized in Table V. 5. Caloplaca citrina sociation This sociation is found on moss cushions and turf and is dominated by nitrophilous lichens. The moss species are primarily Hennediella heimii, Bryum pseudotriquetrum and, to a lesser extent, Bryum argenteum. It is found in Table VII. Ceratodon purpureus sociation composition. Total average cover Ceratodon purpureus Bryum argenteum Bryum pseudotriquetrum Nostoc sp. % Frequency % Cover 100 73 47 13 24 21 0.4 0.6 0.4 Table VIII. Bryum argenteum–Bryum pseudotriquetrum sociation composition. Total average cover Bryum argenteum Bryum pseudotriquetrum Hennediella heimii Ceratodon purpureus Syntrichia sarconeurum Xanthomendoza borealis Prasiola crispa Nostoc sp. % Frequency % Cover 96 75 21 4 4 42 16 8 49 29 13 2.3 0.1 0.13 1.8 1.7 0.1 areas where there is considerable nutrient enrichment from skua gulls. Moisture is primarily derived from melting snow. Plant composition in the 42 relevées is summarized in Table VI. Short Moss Turf and Cushion subformation 6. Ceratodon purpureus sociation This sociation is found on moist ledges and on sandy or silty soils amongst moraine debris and ice rounded boulders, particularly on the raised beach terrace at Botany Bay. In terms of water flow this is the wettest part of the area. The dominant moss is Ceratodon, but Bryum pseudotriquetrum and, to a lesser extent, other mosses such as Schistidium antarctici and Bryum argenteum may be found. Plant composition in the 30 relevées is summarized in Table VII. 7. Bryum argenteum–Bryum pseudotriquetrum sociation This sociation is strongly associated with melt streams and pools, particularly on the raised beach terrace in Botany Bay. The richest bryophyte communities occur where moisture is derived directly from melting snowdrifts and along melt seepage channels and ephemeral streams, or near temporary shallow pools. Reproduction and dispersal is almost entirely by asexual propagules and is particularly prevalent for B. argenteum. Plant composition in the 24 relevées is summarized in Table VIII. Alga subformation 8. Prasiola crispa sociation This sociation occurs on nutrient rich sandy soil in habitats that are sheltered and receive moisture from snowdrifts. Cover, however, may be low. In nine relevées, cover of Prasiola was only 1.8%, with total average cover only 2%. Ordination analysis The ordination produced some clear groupings that coincide mainly with those obtained by the sociation 696 RODNEY D. SEPPELT et al. Fig. 2. For caption see next page analysis (Fig. 2). One difference is the separation into two parts on the ordination of Buellia frigida sociation 1, one dominated by B. frigida and the other by Rhizoplaca melanophthalma, Umbilicaria aprina and several epiphytic cyanobacterial and algal groups. The spread of this group indicates that there is more than one habitat on these boulders which have snowmelt from above and high humidity from water running between them below, as well as a strong effect VEGETATION OF BOTANY BAY 697 Fig. 2. a. Two-dimensional ordination of the species and sample plots based on detrended correlation analysis (DCA) of the cover values of the species. The dimension of the axes is SD-units (standard deviation) so that the variance of the distribution of the species is shown in this biplot. The position of each sample in the biplot is determined by the species occurring in it. The species names have been abbreviated to the first four letters of the genus and the first three of the species, the number following the name classifies the type of occurrence: 7 5 species on cobbles and boulders, 8 5 species on mosses, and 9 5 species on soil. b. As for a but with the sociations produced by the ordination marked with dotted lines. Red lines are lichen dominated and green lines, moss dominated. In each case the number corresponds with the sociation number in the text. c. As for a & b but with the form in which water occurs given for each sociation. Snowmelt means that the water is generated in situ by melting whilst the other categories indicate the water is flowing or ponding and comes from sources outside the Bay. The dotted lines relate to habitat types and different associations (e.g. 5, 7) may occupy the same or similar habitat. from bird fertilization leading to the presence of many nitrophilous lichen species. A defining feature of this sociation is that liquid water is rarely present. The remaining sociations reflect the presence of water, whether flowing or still, as well as the type of substrate. Sociation 2 is dominated by Physcia caesia which, in this area and many other sites along the Ross Sea coast, forms a clear line along runnels with fluctuating water levels. Typically the lichen is submerged only at high flows. This contrasts with the ecology of the species in temperate areas where it is in no way associated with water flows. Sociation 6, which is bryophyte dominated, falls in the same location on the ordination and is dominated by Ceratodon purpureus. In this case the most probable difference is the less stable substrate. Flowing water over unstable but not steep substrates is the location of the second bryophyte dominated sociation, sociation 7, with high cover of Bryum pseudotriquetrum and B. argenteum and this is a very typical occurrence in the Ross Sea region when there is the correct combination of an excellent, regular, slow flowing water supply together with good shelter. Flowing water over a sheltered but well lit rock surface are the apparent conditions for sociation 3, dominated by U. aprina and Rhizocarpon geographicum. Again, for the latter species, this is not the expected habitat from its alpine ecology. Sociation 5, characterized by a dominance of Caloplaca citrina, with the lichens growing primarily on mosses. This is a habitat that is marginal to the main water flows and one in which the lichens do not suffer flooding but clearly obtain a good water supply from the moss beneath them. The presence of nutrients from birds and somewhat drier conditions seems to determine the occurrence of this sociation. Sociation 4, characterized by the presence of Xanthomendoza borealis, occurs typically on periodically wetted, but often unstable rock ledges with a strong bird nutrient influence. The alga Prasiola crispa can occur in similar sites, especially those with pooled water. The analysis clearly indicates the importance of the type of water supply, its regularity, the substrate type, and particularly in Botany Bay, the influence of nutrients derived from the local bird population. 698 RODNEY D. SEPPELT et al. Fig. 3. Vegetation map of Botany Bay, Granite Harbour, southern Victoria Land. Grid interval 5 10 m. Botany Bay vegetation map Vegetation zonation and topography in Botany Bay are shown in Fig. 3. Shape and topography of the seaward margin is influenced by annual events relating to sea ice. With breakout of the sea ice, there is opportunity through ice push to shape the topography. However, while creating disturbance at the seaward margin of the bay, this has little influence on the vegetation. Meltwater passing over areas of moss, particularly B. argenteum, results in the release and subsequent deposition of deciduous apical shoot propagules along the melt channels. Establishment of the moss colonies in the sand and boulders at the shore is almost impossible as the habitat is too unstable. Discussion Since we first visited the area and began the detailed mapping and ecological surveys there has been little obvious change in plant distribution patterns. However, under the influence of global warming trends, increased water flow through or over the vegetation may lead to change. Drainage lines may become wetter or drier, depending on the direction of melt flow over the raised beach terrace, leading to changes in the distribution pattern of the vegetation. Our detailed vegetation map can be used as a baseline reference to monitor such changes. In the Windmill Islands, the only other continental Antarctic region where vegetation mapping on a large scale has been undertaken, there has been appreciable change in the vitality of moss beds over the last 10 years (R. Seppelt, S. Robinson and J. Wasley, personal observations) due to changes in the moisture regime of the habitat. At the Canada Glacier, Taylor Valley, increased summer meltwater flow over the large moss flush has resulted in pronounced lateral spread of the moss. If the warming trends continue to influence continental Antarctic regions we may expect significant change to the extent of the moss cover. Careful and accurate mapping of the vegetation in selected areas such as these (particularly Canada Glacier, Botany Bay, Beaufort Island and Cape Hallett in Victoria Land, the Windmill Islands region, Wilkes Land) has provided an important tool for assessing the impacts of climatic change on the continental Antarctic terrestrial ecosystem. VEGETATION OF BOTANY BAY The surveys carried out in this investigation fully confirm that Botany Bay is one of the richer sites for lichen and bryophyte biodiversity in continental Antarctica. The total of 29 lichen, nine moss and one liverwort species is practically identical to the numbers reported for Wilkes Land by Smith (1988), a site that is about 11 degrees latitude further north (668S compared to 778S for Botany Bay). Around thirty lichen species are also reported for Casey and Davis stations, also at about 668S latitude (Green et al. 2007). It is probable that Edmonson Point, Terra Nova Bay, has higher numbers of species but the 56 species reported from there (Castello & Nimis 1995) include lichens from several sites further north. The similarity in total species numbers across the whole of continental Antarctica suggests that the cline in biodiversity seen as one moves south along the Antarctic Peninsula (Peat et al. 2007) does not continue over continental regions. Further indicators of the special nature of Botany Bay are the southernmost records in Antarctica for a liverwort, Cephaloziella varians, for the lichen Turgidosculum complicatulum, for the moss Bryoerythrophyllum recurvirostrum and probably also for Ceratodon purpureus. Most are about three degrees latitude further south than the nearest record to the north in the Terra Nova Bay area. The results of the vegetation analysis also agree in the main with those of Smith (1988) for Wilkes Land and Cannone & Seppelt (2008) and Castello & Nimis (1995) for central and northern Victoria Land, respectively. The latter two studies covered a larger geographic spread than this study and the level of agreement suggests that there is limited diversity of vegetation types in the Ross Sea region. Our groups 1 and 2, B. frigida sociation on rocks and the P. caesia dominated fluvial sociation, agree with 2A and 2B of Cannone & Seppelt (2008). Similarly, our groups 3 and 4 correspond to group 3, our group 5 to group 4, and the bryophyte dominated groups 6 and 7 to groups 6.1 and 6.2 of Cannone & Seppelt (2008). The main determinants of the occurrence of the different sociations appears to be the source of water, whether solely from snowmelt or snowfall, or from some form of melt stream. Sites influenced primarily by snow cover are lichen dominated while those influenced by meltwater are either mixed bryophyte/lichen or, in the wetter places, bryophyte dominated. Sociations are also influenced by the regularity and speed of water flow, and the type of substrate, especially whether it is loose gravel or solid rock. Some species show different ecologies in Antarctica compared to their temperate or alpine habitats or even from elsewhere in Antarctica. Rhizocarpon geographicum is typically found in Botany Bay and nearby localities where water flows slowly over a near vertical solid rock surface. Physica caesia is found as a distinct line along watercourses at a level where it is regularly submerged each day at peak summer melt flow. Neither species is associated with flowing water elsewhere. The moss C. purpureus is typically reported from drier sites in 699 flushes, such as at Edmonson Point (Smith 1999), but it occurs in the wettest habitats at Botany Bay. Possibly the greatest difference between Botany Bay and the other sites to the north is the complete absence of Usnea species. This is not easy to explain as U. antarctica is reported from Kar Plateau, just across Granite Harbour from Cape Geology, and U. sphacelata is reported from 848S at Mount Kyffin, in the southern Ross Sea. Abundant populations of U. sphacelata and U. antarctica also occur on Ross Island at sites that are visible from Cape Geology. In contrast, the specimens of Umbilicaria aprina at Botany Bay are some of the larger specimens reported in Antarctica and were reported to be as large as dinner plates by Scott’s western geological party in 1912 (Schroeter et al. 1993). The generalization of Smith (1988) that three main groups occur, one dominated by lichens, one by bryophytes and a third in which lichens are epiphytic on bryophytes seems to hold. There seems little doubt that the extremely moderate summer climate in Botany Bay, the excellent water supply and nutrient input from the skua colony are the main determinants of the rich vegetation. The north facing aspect, the enhanced radiation from the almost everpresent sea ice and protection from strong winds afforded by cliffs to the south and west, means that very warm conditions occur for about two months each year. At the beginning of January there are a small number of days that are almost frost free with maximal air temperatures close to 108C. The presence of the corrie to the south and above the Bay, and of a perched ice field above, ensures a steady source of meltwater in summer. Winter snowfalls appear to also be regular but not excessive, only about 40 cm depth in total. Shallow snowfalls are advantageous in this area as late lying snow acts as an insulator, keeping the ground cold and delaying the onset of active metabolism (Pannewitz et al. 2003) until air temperatures are warmer and water supply more reliable. Even so, it is dangerous to assume that a high visible biomass also means high productivity. The studies by Kappen et al. (1998) clearly show that B. frigida thalli on boulders are only active for a small number of hours each year. At least for this species, growth rates are exceedingly variable, ranging from 1.0 mm per 100 years in the Taylor Valley to 6.9 mm per 100 years at Cape Hallett (728S) (Sancho et al. 2007). We are now able to compare descriptions from three sites at about 778S latitude: Canada Glacier flush, an extensive area of bryophyte dominated vegetation in lower Taylor Valley (Schwarz et al. 1992); Beaufort Island, an area of c. 1 ha of almost pure B. argenteum on a north facing slope backed by a glacier wall and with an extensive skua colony (Seppelt et al. 1999), and Botany Bay (present study). A comparison on the basis of lichens is not possible as they are almost absent except at Botany Bay. The bryophytes are interesting in that there are only three species at Canada Glacier, ten at Botany Bay (one liverwort) and two (one dominant moss and one very minor) on Beaufort Island. 700 RODNEY D. SEPPELT et al. A possible explanation for these differences could be the level of external nutrition. There is almost no external nutrient supply at Canada Glacier except that brought by dust or glacier meltwater. At Botany Bay there is a moderate input from the small skua colony and at Beaufort Island a significant input from the extensive skua colony. It appears that there may be an optimal nutrient level for bryophyte biodiversity and that too little, or especially an excess, will lead to lowered species numbers. It is also of note that at Cape Hallett, where there is an extensive bryophyte flush adjacent to skua nests and a very large Adélie penguin colony, there is only one moss species, B. argenteum, in the main flush area. This is an equivalent situation to Beaufort Island and suggests that only B. argenteum can take advantage of these high nutrient zones. In other coastal areas of continental Antarctica, such as the Syowa Coast (408E) (Kanda 1981, 1987, Kanda & Inoue 1994), B. argenteum is the dominant moss near to the shore, but to the east, between 508E and 1608E, this species appears to be absent, being replaced by B. pseudotriquetrum. Despite the growing interest in the possible effects of climate change on Antarctic vegetation it seems that we are a long way from being able to successfully predict vegetation shifts in the Ross Sea region. In the maritime Antarctic Peninsula a clear biodiversity cline exists and must depend on a climatic variable, probably water availability. However, in the Ross Sea region there is little evidence of a clear cline, similar vegetation types seem to exist all along the coast and even to more distant sites, like Wilkes Land. This is almost certainly a result of the desert conditions with suitable habitats only becoming available where a regular and substantial water supply is available. In the Windmill Islands (668S) there has been a marked rapid change in the vitality of the mossdominated areas (Melick et al. 1994, Melick & Seppelt 1997, Wasley et al. 2006, Seppelt et al. unpublished observations) with an increase in abundance of epiphytic lichen cover and moribund moss being associated with a drying of the vegetation. Distributional changes, particularly in algae and mosses and probably relating to altered water flows have also been reported from Cape Hallett (Brabyn et al. 2005, 2006. Some properties of the vegetation, like lichen growth rate (Sancho et al. 2007), DNA damage in mosses following greater exposure to higher levels of incident UV radiation (Turnbull & Robinson 2009), and changes in flavonoid chemistry resulting from changes in atmospheric ozone levels (Ryan et al. 2009) do seem to be possible indicators of climate change. 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