Colonization and demographic structure of Deschampsia antarctica and Colobanthus quitensis along an altitudinal gradient on Livingston Island, South Shetland Islands, Antarctica

Figures & data

Fig. 1.  Distribution and abundance of Deschampsia antarctica and Colobanthus quitensis in the area of the Spanish Antarctic base (BAE) Juan Carlos I on Livingston Island, South Shetland Islands, Antarctica. The locations of the studied samples are shown. The location of a recently colonized (RC) site is indicated near Española Cove (Caleta).

Table 1. Characteristics of the flat sites (F), peripheral sites (P) and a recently colonized site (RC) along the altitudinal gradient in the study area.

Altitude (m a.s.l.) and site type	Characteristics	Soil depth (cm)	Soil pH of bare ground
10 RC	Pebbles, flat raised beach	0–1	–
10–20 F	Flat top of a morainic deposit	2–10	6.4–6.7
10–20 P	Slope running down from flat top	1–2	–
40 F	Flat top of a ridge	8 to >12	–
40 P	North-east slope of the ridge, stable, with some stony soil	3–10	–
97 F	Flat top of an erosion platform, with stones	2–5	5.4–6.7
97 P	Scarce slopes with different expositions running down from the flat top of the platform, stony, gravely soil	0–2	6.1–6.7
110 F	Flat top of a morainic deposit	1–2	–
110 P	Scarce slopes with different expositions running down from the flat top of the morainic deposit, stony, gravely soil	ca. 1	–
147 F	Flat top of a morainic deposit	1–3.5	6.8–7.1
147 P	Scarce slopes with different expositions running down from the flat top of the morainic deposit	0–1	6.5–7.0

Table 2. Estimation means of ages (years) of Colobanthus quitensis cushions with different diameters at two altitudes.

Diameters (cm)	20 m a.s.l.	147 m a.s.l.
1	2.7	3.4
3	8.1	10.34
5	13.5	17.24
7	18.9	24.13
9	24.3	–
11	29.7	–
13	35.1	–
15	40.5	–
17	45.9	–

Fig. 2.  Percentage cover of Antarctic native vascular plants, mosses, lichens and bare ground at flat sites (F), peripheral sites (P) and a recently colonized site (RC) along the altitudinal gradient in the study area.

Fig. 3.  Proportion of size classes (plant diameter, excluding seedlings) of Deschampsia antarctica and Colobanthus quitensis in populations at flat sites (F), peripheral sites (P) and a recently colonized site (RC) along the altitudinal gradient in the study area.

Table 3. Mean (±SE) and diameter ranges (in brackets) of Deschampsia antarctica and Colobanthus quitensis diameters (current season seedlings were not considered) at flat and peripheral sites at each altitude.

	10–20 m a.s.l.	40 m a.s.l.	97 m a.s.l.	110 m a.s.l.	147 m a.s.l.	p
	Flat sites
D. antarctica diameters (cm)	5.36 (±0.42) [0.20–20.0]	6.36 (±0.54) [1.30–15.0]	3.61 (±0.36) [0.30–7.0]	5.88 (±0.60) [2.0–11.0]	4.86 (±0.43) [1.0–10.0]	n.s.
C. quitensis diameters (cm)	4.31 (±0.34) [0.20–18.0]	5.02 (±0.57) [0.3–12.0]	3.15 (±1.18) [0.2–7.0]	5.26 (±0.70) [3.0–7.0]	4.81 (±0.41) [1.0–8.5]	n.s.
	Peripheral sites
D. antarctica diameters (cm)	2.16 (±0.19) [0.2–0.6]	1.63 (±0.18) [0.2–5.0]	2.22 (±0.26) [0.3–6.0]	2.53 (±0.21) [0.8–5.0]	3.02 (±0.24) [1.0–7.0]	**
C. quitensis diameters (cm)	0.82 (±0.07) [0.2–5.0]	0.93 (±0.11) [0.2–4.0]	1.54 (±0.25) [0.2–10.0]	1.75 (±0.22) [0.2–4.50]	1.76 (±0.26) [0.1–7.0]	***

Note: Asterisks indicate the level of statistical significance between the altitudes: ***p<0.001; **p<0.01; n.s. not significant.

Table 4. Mean (±SE) of Deschampsia antarctica and Colobanthus quitensis seedlings and individuals per m², as well as the mean diameters (excluding seedlings) for each type of site (altitude 10–40 m a.s.l.).

Parameters	Flat sites	Peripheral sites	Recently colonized site	p
D. antarctica seedlings	2 (±2)	21 (±7)	4 (±4)	*
C. quitensis seedlings	179 (±71)	1005 (±170)	8 (±8)	***
D. antarctica individuals	120 (±10)	175 (±12)	15 (±8)	***
C. quitensis individuals	112 (±17)	319 (±50)	62 (±16)	***
D. antarctica diameters (cm)	5.67 (±0.34)	1.95 (±0.13)	2.61 (±0.42)	***
C. quitensis diameters (cm)	4.49 (±0.29)	0.85 (±0.06)	1.18 (±0.20)	***

Note: Asterisks indicate the degree of statistical significance between the habitats: ***p<0.001; *p<0.05.

Fig. 4.  Density of individuals of Deschampsia antarctica and Colobanthus quitensis at flat sites (F), peripheral sites (P) and a recently colonized site (RC) along the altitudinal gradient in the study area (standard error bars shown).

Fig. 5.  Density of seedlings of Deschampsia antarctica and Colobanthus quitensis at flat sites (F), peripheral sites (P) and a recently colonized site (RC) along the altitudinal gradient in the study area (standard error bars shown). Note different scales for the two species.

Fig. 6.  Seedling survival of Deschampsia antarctica and Colobanthus quitensis in peripheral sites after one year based on the assumption that the numbers of emerged seedlings during 2001 and 2002 were the same.