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Antarctic Science 13 (2): 126-134 (2001) 0 Antarctic Science Printed in the United Kingdom

Vegetation abundance and diversity in relation to soil nutrients and soil water content in Vestfold Hills, East Antarctica MICHELLE R. LEISHMAN' and CHRISTIE WILDz Department of Biologrcal Sciences, Macquarie Universiy, NSW 2109, Australia 'Corresponding author 'Present address: 41 Barkala Ave, Westleigh, NSW 2081. Australia

Abstract: Eighteen paired sites (adjacent to vs away from sea bird nests) and six transects (downslopeof nests) across Vestfold Hills were sampled for vegetation, soil nutrients, soil water content and percent rock cover. Three moss and 17lichen specieswere recorded, including a new record for the lichen Sarcogyneprivigna. Sites adjacent to nesting areas generallyhad hgher soil N and P than sites away from nesting areas; however, larger differencesbetween site locationsthan within site pairs suggests considerablevariation in nutrient input between nesting areas and/or redistributionof nutrients by meltwater around nests. Along transects below nesting sites, average soil total N declined from 0.22% to 0.05% within 2 m from the nest, whle average total P declinedmore gradually from 2343 ppm P to 697 ppm P at 30 m from the nest. Moss and lichen species diversity and mean lichen species abundance were higher in sites adjacent to compared with away from nests. Data from site pairs and transects showed that lichen diversity and abundance increased with increasing soil nutrients, with soil P having a stronger influence than soil N. In contrast, soil nutrients were not significantly associatedwith moss diversity or abundance. Instead, number of moss species and abundance were positively associated with soil water content. Received 28 February 2000, accepted 5 December 2000

Keywords: lichen, moss, nitrogen, ornithogenic, phosphorus, soil water content Introduction

& Seppelt 1995, Smith 1995, Mellick & Seppelt 1997).

There is increasinginterest in understanding the mechanisms which control species' distributions,abundance anddiversity, both globally (Rosenzweig 1995) and in Antarctic environmentsparticularly (Greenet af.1999). This isbecause global climate change and human impact through habitat disturbance are important processes whch currently threaten biodiversity, and it has become critical to understand the underlying mechanisms which determine biodiversity if we are to minimise its loss. At the landscape scale, the availability of ice-free areas determines the distribution of terrestrial vegetation in Antarctica. The traditional approach to understanding the diversity and abundance of Antarctic terrestrial vegetation within these ice-free areas has been to describe species and their distribution, list floristic groupings and relate these to apparent environmental factors (Pickard 1986). Good examples of t h s approach are the studies by Pickard & Seppelt (1984), Pickard(1986),Broady(1989), Inoue( 1989), Gremmen etal. (1994), Hovenden & Seppelt (1995) and Melick & Seppelt (1997). Four major environmental factors have been identified in qualitative studies as important influences on Antarctic terrestrial vegetation: moisture availability,nutrients,salinityand microtopography(affecting both exposure and water availability) (Seppelt & Ashton 1978, Broady 1989, Kappen 1985, Pickard 1986, Seppelt 1986a, 1986b, Inoue 1989, Ryan & Watkins 1989, Schwartz et al. 1992, Kennedy 1993, Gremmen et al. 1994, Hovenden

Apart from observationsof these general patterns, there has been little quantitative work which has attempted to correlate any of these four environmental factors with abundance or diversity of terrestrial vegetation in continental Antarctica Ryan & Watkins (1989) measured soil concentrations of major plant nutrients along bird-influenced gradients at an inland nunatak group, assessed microhabitatand related these to plant cover. Theyfound that water availability,as determined by microhabitat, was the main determinant of vegetation abundance within habitats, but that nutrient availability from birdcolonieswas the main determinant ofvegetationabundance between habitats. Gremmen et al. (1994) classified epilithic macrolichenvegetationin the Antarctic Peninsula and related community composition to nutrient status and microclimatic conditions. In thispaperwe quantitativelyassess therelationshipbetween abundance and diversity ofboth mosses and lichens with soil P, soil N, soil water content and percent rock cover in Vestfold Hills, East Antarctica. Both water availability and nutrients have been suggested as the major limiting factors for plant growthin continentalAntarctica. The major sourceof available water is from snow and ice when melting occurs. The major source of nutrients such as P and N are nesting coloniesof sea birds, such as snow petrels (Pagodroma nzvea) (Ryan & Watkins 1989). The specific questions we address are: 1) How does proximity to sea bird nesting sites affect soil 126


nutrient content? 2) How does the abundance and diversity of moss and lichen species vary between areas of enriched nutrient levels around sea bird nesting sites and areas away from nesting sites? 3) How does the abundance and diversity of moss and lichen species vary along gradients of soil nutrients within areas of nutrient enrichment?

4) Can the abundance and diversity of moss and lichen species also be correlated with other environmental factorssuch as soil water content and percent rock cover? Study area Vestfold Hills is an area of 413 km' of ice-free rock in East Antarctica (Fig. 1). Pry& Bay lies to the north and west of the hills, while the east isboundedby the continental ice sheet, and the south by Sarrsdal Glacier. The relief is generally low, with the highest point being 158 m a.s.1. The eastern section is rugged in comparison with the generally flat western areas. Mid-summer mean temperatures are close to 0°C while temperatures from May to September average from -15' to -18°C (Streten 1986). The effect ofkatabatic winds is strong adjacent to the ice edge, but dissipates markedly across the Hills so that they have little effect in the western coastal regions. At least 22 species of lichens (Seppelt 1986a) and seven species of moss have been recorded or are thought to occur (Seppelt 1986b)in Vestfold Hills. The broadscale patterns of lichen and moss distribution have been described by Pickard (1986) and Seppelt et al. (1988). These are: reduced species numbers close to the ice sheet and Sarrsdal Glacier, reduced speciesnumbers in the salt-affectedwestern section compared withthe easternsection,aiidincreasedabundanceanddiversity associated with elevated land.


size, aspect, slope, geomorphologcal character and proximity to snowbanks, was sampled in the same way. At each of the sampling sites, five soil samples, to a maximal depth of 10 cm, were collected, bulked and analysed for total N, total P and water content. Transects Six transects running downslopefrom a bird nesting site were selected. The six transects were located in three areas (Fig. 1) and were locateda minimum of 100m apart, thusare considered independentofeach other in the analysis of the data. Quadrats were recorded at 10 points along each transect: in the nesting area, 1 m, 2m, 3 m, 5 m, lorn, 15 m,20m, 25mand30m downslope. At each distance, a 25 cm x 25 cm quadrat was sampled for % cover of all moss and lichen species present, and the %rock cover was estimated. A soil sample, to a maximum depth of 10 cm, was collected at each quadrat and analysed for total N and total P, as well as for water content. For three of the transects, plant material from three species (two mosses Bryum pseudotriquetrum and Sarconeurum glaciale and one 1ichenXanthoriaelegans) was collected and analysed for total N and total P.

Methods Field work was conducted in Vestfold Hills from early December 1992 until mid-February 1993. Paired sites Eighteen paired sites across Vestfold Hills were sampled, giving a total of 36 sampled sites (Fig. 1). Paired sites were selected as follows:an area of nutrient enrichment was chosen i.e. adjacent to a snow petrel (Pagodroma nivea (Forster)) breeding site or a south polar skua (Catharacta maccormicki Saunders) nesting area. Twenty quadrats (25 cm x 25 cm) were randomly selected and recorded for % cover of all moss and lichen species present. In adchtion, the % rock cover (including bedrock, boulders and pebbles) in each quadrat was estimated. A nearbymatchingsite ofthe sameapproximate

Sarrsdal Glacier

Fig. 1. Vestfold Hills showing location of all sampling sites Paired sites 1-18 are shown by their numbers, while location of transects is shown by the closed diamond symbols (two transects at each of the three locations).



Laboratory analyses

analyses was mean species abundance, pooled for lichen and moss species separately (i.e. calculated as the total % cover across all species (moss or lichen) divided by the number of species present at the site). Percent data were arcsine transformed (% rock cover, % soil water content, % lichen cover, % moss cover) to fulfil assumptionsof normality. Each of the four environmental variables (total N, total P, % rock cover, % soil water content) were assessed as explanatory variables for moss and lichen species mean abundance and species number. F-ratios were used to test for signlficance in the analyses of species mean abundance, while Poisson error distribution was used to test for significance in the analyses of species number. Each variable was fitted to the data sequentially, in order to assess the explanatory power of each

Percent soil water content was measured as the wet weight of soil minus the dry weight of soil, as a percentage of the wet weight of soil. Soil was air-dried in the laboratory at Davis station for two weeks. Total N of both soil and plant samples was measured using the KjehldaN Method, while total P of soil and plant samples was measured using acid digest and colorimetric methods (Lambert 1982). Statistical analyses

General linear modelling was performed on the dataset of all sites, using the GLIM Version 3.77 Statistical Package (Payne 1986). The measure of abundance used in the Site pairs.

Table I. Summary of data for the paired sites. For each site, A was selected in the field as nutrient-enhanced due to proximity to nesting birds while B was selected as the matching non-enhanced site. Numbers in bold indicate a significant difference between sites A and B within a site pair (t-test, P = 0.05).



% soil

Total N (%)

Total P (PPW




No. moss species

No. lichen species

Mean % cover moss species

Mean % cover lichen species

1A 18

Lichen Valley Lichen Valley

8.8 4.2

0.06 0.01

1010 1I92

53 43

3 2

4 7

0 93 0 18

0.75 0.11

2A 2B

Lichen Valley Lichen Valley

4.7 1.5

0.09 0.02

1194 1201

82 77

3 2

7 10

1 60 138

0.91 4.34

3A 3B

Lichen Valley Lichen Valley

0.7 0.4

0.00 0.01

1161 1014

62 61

2 0

8 7

0 63 0

1.78 1.91

4A 4B

Ellis Rapids Ellis Rapids

3.3 1.7

0.06 0.01

1716 784

62 36

2 0

12 7

0 50 0

1.19 1.00

5A 5B

Ellis Rapids Ellis Rapids

4.6 8.1

0.03 0.01

729 59 1

75 64

3 3

10 2

0 85 2 23

0.52 0.08

6A 6B

Mossel Lake Mossel Lake

16.7 7.5

0.08 0.02

867 647

55 33

3 2

4 5

3 60 2 63

0 25

7A 7B

Mossel Lake Mossel Lake

0.6 1.4

0.02 0.00

876 696

76 64

0 0

7 5

0 0

1.29 0.17

8A 8B

Laternula Lake Laternula Lake

3.6 5.6

0.02 0.00

1644 1200

50 90

0 0

10 8

0 0

2.89 2.77

9A 9B

Trajer Ridge Trajer Ridge

6.8 7.6

0.27 0.02

1361 538

82 71

0 1

8 7

0 0 03

3.6 0.38

10A Trajer Ridge 10B Trajer Ridge

2.6 0.5

0.02 0.01

917 638

89 92

3 2

13 12

2 09 0 51

1.38 0.5

11A Caloplaca Bluff 11B Caloplaca Bluff

1.2 0.8

0.17 0.02

1033 602

81 91

1 0

9 8

0 25 0

2.97 1.28

12A 12B 13A 13B

6.7 5.1 3.3 1.6

0.06 0.01 0.19 0.03

1351 625 1765 1306

74 77 65 57

3 2

11 10

4.13 0.86

1.25 0.23

1 0

11 8

2.00 0

4.57 1.71

14A Boulder Hill 14B Boulder Hill

3.2 2.6

0.01 0.00

616 568

64 46

3 2

13 8

7.43 1.00

2.16 0.46

15A Boulder Hill 15B Boulder Hill

12.0 1.7

0.07 0.01

963 746

61 87

3 2

8 9

2.47 0.79

1.81 0.16

16A Sersdal Island 16B Sersdal Island

3.7 0.5


770 671

70 63

2 0

12 8



2.49 0.33

17A Pioneer Crossing 17B Pioneer Crossing

8.9 4.6

nla nla

nia nla

42 46

2 0

12 10

12.76 0

2.41 0.3

14.3 0.3

nla nla

nla nla

55 29

3 0

9 10

3.79 0

1.63 0.81

Caloplaca Bluff Caloplaca Bluff Lichen Valley Lichen Valley

18A Lichen Valley 18B Lichen Valley





bird debris had been redistributed so that the two sites within the pairs were indistinguishable, and this is reflected in their soil nutrient levels. Consequently,these three sitesare excluded from the comparison of sites within pairs. Secondly, it is apparent that even though there was a difference in total soil N and P within each of the remaining site pairs, the differencesbetween sites at different locations are much larger than differences between pairs at each site. For example, total P at site 13 was 1765 ppm and 1306 ppm, compared to 616 ppm and 568 ppm at site 14. Thus there is no consistent difference in soil P and N between locations adjacent to nesting areas and locations not adjacent to nesting areas, suggesting that there is signlficant local redlstribution of soil N and P, and considerable variation in nutrient input between nesting areas. Consequently, analysesproceed at two levels: (1) comparisonbetween sites within each site pair, and (2) comparison across all sites pooled together.

variablewhen fitted to the data first, and when fitted after other significant variables. Sites with missing data were excluded from the analysis, leaving a total of 32 sites, as soil nutrient levels were not analysed for sites 17 and 18. Transects. In order to assess the importance of each of the measured environmental variables (total soil N, total soil P, soil water content and % rock cover) in determining moss and lichen species abundance along a gradient away from nesting sites, the data from all transects were pooled and analysed using GLIM Version 3.77, following the same procedure outlined above.

Results Paired sites

The results for the 18 paired sites are summarized in Table I. A total of three moss species and 17 lichen species were collected (Table11). All specieshad previously been recorded for Vestfold Hills, with the exception ofthe lichen Sarcogyne privigna, which was found at Trajer Ridge (site 12). Two points need to be made about the soil nutrient results. Firstly, and contraq to expectations, not all site pairs had a difference in total P and total N between the paired sites (exceptions were sites 1 , 2 and 3 ) . These three sites were on shallow slopes or valley floors in Lichen Valley. When the sampling was done early in the season, the two sites of each pair appeareddistinct in terms ofproximityto nesting sites and abundance of bird debris. However, when these sites were visited later in the season, after considerable snow melt, the

Comparison between sites within site pairs

Of the total of 18site pairs, three showed no difference in soil N or P and so are excluded (sites 1-3). Two site pairs (sites 17 and 18) do not have data on soil N and P, but we have included these in the within site comparisons as they were on steep slopes where redistribution of soil nutrients between the sitepairswouldbeminimal. Ofthe 15remainingsitepairs, the number of moss species present was higher in the nutrientenhanced site in 11 of the paired sites, compared to one site pair where there were more moss species present in the lower nutrient site and three site pairs where moss species numbers were the same (Table I). Of the six site pairs where moss

Table 11. Abundance of three moss and 17 lichen species recorded during sampling in Vestfold Hills between December 1992 and February 1993 (paired sites 4-18). Abundance in nutrient-enriched and non-enriched sites is shown as mean YOcover. s d refers to standard deviation while P denotes P-values for paired I-tests (df = 14). ~



B r y m pseirdotriqirehirm (Hedw.) Gaertn., Meyer et Scherb. Hennediella heimir (Hedw.) Zander Sarconeirrirm glacmle (Ho0k.f. et Wils.) Card. et Bryhn Acarospora gwynii Dodge et Rudolph Acarospora willramsir Filson Birelliafirgrda Darb. Calopluca athallina Darb. Caloplucu crrt’ina (Hoffm.) Th. Fr. Candelariellaflava (Dodge et Baker) Castello et Nimis Lecanoru expectans Darb. Lecidea cancrlformis Dodge et Baker Lecidea spp. Physcia caesia (Hoffm.) Hampe Pleopsidiiim chlorophanirm (Wahlenberg) Zopf Rhizoplaca melanophthalma (Ram.) Leuck. et Poelt Rinodina olivaceobriinnea Dodge et Baker Sarcogyne privrgna A. Massal. Wmbilicarra aprina Nyl. Xanthoria elegans (Link) Th. Fr. Xanthoria mawsonri Dodge

moss moss moss lichen lichen lichen lichen lichen lichen lichen lichen lichen lichen lichen lichen lichen lichen lichen lichen lichen


cover non-enriched sites mean sd

0.60 0.09 0.53 0.09 0.06 4.08 0.02 0.25 0.07 0.28 0.02 0.21 < 0.01 < 0.01 0.33 0.02 < 0.01 0.05 0.23 0.04

1.05 0.34 1.01 0.16 0.11 5.89 0.08 0.26 0.16 0.20 0.02 0.35 < 0.01 < 0.01 0.35 0.08 0.03 0.15 0.22 0.07


cover nutrient-enriched sites mean sd 3.35 1.08 2.35 0.18 0.65 9.2 1 0.14 1.95 1.52 2.19 0.03 0.55 0 26 0.01 0.47 0.11 0.01 0.44 2.93 0.6 1

5.96 1.54 2.99 0 39 0.83 8.76 0.16 1.33 2.63 2.11 0.09 0.80 0.84 0.02 0.80 0.14 0.03 0.86 2.12 1 .oo

P ns 0.028 0.035 ns 0.017 0.009 0.012

< 0.001 0 042 0.004

ns 0.028 ns ns ns 0.016 IIS

ns < 0.001 0.038




abundanceof lichen specieswas higher in the nutrient enriched site, and these differences were significant(t-test, P= 0.05) in 10 of the site pairs.


0 > 0

8 C

Comparison using pooled data for all sites





8 c m












ln a ln v)


8 0.01






Soil moisture ("A)

Fig. 2. Relationship between mean moss species abundance and soil water content, using data pooled from the paired sites.

specieswerepresentatbothsites withina site pair, mean moss species abundance was significantlygreater (t-test, P = 0.05) in the enriched nutrient site at two out of six site pairs. The number of lichen species present was higher in the nutrient enriched site in 12ofthe 15site pairs, and lower in the remaining three site pairs. In all 15 site pairs, the mean

O 0 0 0 0

Abundance. The mean abundance of two of the three moss speciesfound (Hennediellaheimii and Sarconeurum glaciale) was significantly higher in nutrient-enriched sites (Table 11). The mean abundance of 10 of the 17 lichen speciesfound was significantly higher in nutrient-rich sites (Table XI). The most abundant lichen species in the nutrient-enriched sites were consistently Caloplaca citrina, Lecanora expectans, Xanthoria elegans, and X. mawsonii. In contrast, in the nonenriched sites, the most abundant lichen species were consistentlyRhizoplaca melanopthalma,Acaraspora gwynii and Lecidea spp. The species C. citrina, L. expectans, X. elegansandx. mawsonii didoccw at the non-enriched sites but at much lower abundance levels than at enriched sites. When all environmentalfactorswere fitted to the null model for mean YOcover of moss species, only YOsoil water content was capable of explaining signlficant deviance (F,,3,= 7.1, r'= 0.23, P < 0.05). Moss species abundance was positively correlatedwith% soilwatercontentacrossthe 32 sitespig. 2). Both total Nand total P could explain siglllficant deviation from the null model for mean % cover of lichen species when considered first (total N Fl,3,= 8.49, r3= 0.27, P < 0.01; total P Fl,3,= 11.41, r Z = 0.37, P < 0.005). Only total P had signlficant explanatory power when considered after total N (F,,3,=6.64, P < 0.05),explaining 16.1% ofvariation in mean lichen species abundance after total N. Abundance of lichen species increased with an increase in both soil N and P across the 32 sites (Fig. 3).


. 0









Soil Total N (%)


. 0

0. 0.

0 0 0 I




700 800



Soil Total P (ppm)

Fig. 3. Relationship between mean lichen species abundance and soil nutrients, using data pooled from the paired sites.




0.3 0.5









Soil moisture (3' %)

Fig. 4. Relationship between number of moss species and soil water content, using data pooled from the paired sites.


Dzvemzfy. Only %soil water content was a sigruficant explanatoryvariable for number of moss species present at a site (P < 0.01), accounting for 17.2% of the variation. The number of moss species present at a site increased with soil water content (Fig. 4). The only signifcant explanatory variable for number of lichen species present at a site was the % rock cover (I")= 0.15, P < 0.05), where number of lichen species present was positively correlated with YOrock cover (Fig. 5).

Transects The data for soil total N, total P, water content, and mean % cover of lichen speciesand moss species were averaged for each distance along the six transects (Fig. 6). It is clear that at the topofthetransect, i.e. withinthenestingsite, bothtotal soil Nand total P are high, soil water content is low, and abundance of both moss and lichen species is low. For soil N, there is a dramatic difference between soil within the nesting site compared with away from the nesting site while, in contrast, soil P continues to decline from a peak within the nesting site with increasing distance away from the nest. Soil water content shows a gradual increase downslope of the nest. Lichen abundance increases immediately downslope of the nesting area, then gradually declines. In contrast, moss abundance increases immediately downslope of the nesting area, and continues to increase downslopeup to 20 m &stance from the nesting site, before declining again. The variables % soil water content and 'YOrock cover were both found to explain significantdeviancefrom the null model in moss species mean abundance when considered first (soil water content F,,,, = 6.2, r' = 0.13, P < 0.02; rock F,,,, = 7.3, I")= 0.15, P < 0.01), however neither could account for significant variation independently of the other. Moss



abundance increased with increasing soil water content and declined with increasing rock cover. Only % soil water content explained significant deviance from the null model for mean abundance of lichen species (F,,49= 5.01, P < 0.05,) accounting for 11.9% of variation. However, inspectionof the data revealed a non-linear response of lichen abundance to total soil N and P, where abundance was low at both very low and very high levels of soil N and P. Consequently, the data were reanalysed excluding quadrats where total Nexceeded0.30 YOortotalPexceeded 3000 ppm. This resulted in a total of 48 quadrats analysed. The results show that % rock cover (F1,47= 7.1, I")= 0.04, P < 0.05),% soil watercontent (FI,,,=5.6,rJ=O.12, P

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