THE ALTIPLANO
The altiplano or puna is a highland plain in the central Andes region of South America and
includes parts of Perú, Bolivia, Chile and Argentina. The Food and Agriculture Organisation
(FAO) classified the puna ecosystem as ‘Andean dry steppe climate’ where grasses
predominate, equivalent to sub-alpine humid paramo or alpine tundra (Cueto, Ponce et al.
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1985). The northern border of this region is the Cajamarca Province in Perú (7 50' S), and
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the southern border reaches 23 38 S (Copiapó Province) in Chile and 27 50' S (San Juan
Province) in Argentina. The altiplano comprises interior mountain blocks, enclosing extensive
high plateaux and intermountain basins that have a mean altitude of 4,000 m (Baied and
Wheeler 1993). These altitude-related features, together with variations in plant cover and
topography, produce complex local and regional weather variations (Baied and Wheeler
1993).
There is a long dry season and a short wet season, with 75% of the rainfall occurring from
December to March. The atmospheric pressure at 4,000 m is 40% lower than that at sea level
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(Aceituno 1997) and air density is 35% lower (635 hPa at 10 C in the altiplano and 1,010 hPa
at 20oC at sea level) (Aceituno 1993). Solar amplitude is moderate, the total solar radiation in
December (the Southern Hemisphere mid-summer) being only 1.7 times higher than in June
(Southern Hemisphere mid-winter). The highest solar radiation period coincides with the end
of spring; this is due to high cloud cover during summer. On average, ultraviolet radiation in
the altiplano is 20% higher than at sea level. The lower greenhouse effect of the altiplano
atmospheric gases makes the atmosphere more transparent to radiation, causing less
counter radiation for infrared. Thus, nocturnal surface heat loss is markedly faster in this
region compared to that at sea level (Aceituno 1997).
The proximity to the Equator means that the highest mean temperature is reached at the end
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of spring (20 C in November). The minimum mean nocturnal temperature shows a higher
variation than the mean maximum temperature because of the rapid surface heat loss at night
when the skies are clear. The greenhouse effect caused by more cloud cover during summer
makes the nocturnal temperature fall less extreme (November mean minimum temperature:
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0-5 C). The maximum mean temperature reaches 20 C in November and 13 C in winter as
an overall reference for the entire altiplano. In summer (December-February), temperatures
fall to a minimum of 1-5o C, and -11o C in winter (June-August). Therefore, conditions during
the year produce a higher thermal variation between maximum and minimum during winter,
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with up to 25 C of variation between day and night. Moreover, the mean air temperature is
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reduced by 6.5 C for every 1,000 m of altitude (Arroyo, Squeo et al. 1993).
The wind regime is highly variable and strongly influenced by local geographical conditions,
with a major east-west trend in winter with drier winds, and a west-east trend with wetter
winds in summer. Mean maximum winds can reach 97 km/h, and strong winds are present
nearly every day, becoming most intense after noon. Humidity varies between summer and
winter. During the rainy season humidity is high as a consequence of the Amazonian front;
during winter it is low due to the main effect of the eastern front. El Niño phenomena can alter
rain patterns, with less rainfall during summer (Arroyo, Squeo et al. 1993). Rainfall is lower
than 700 mm and declines from north to south. It is concentrated in summer, with 90-95% of
rain between November and March. The between-year variation fluctuates between 0.1 and 2
times the mean (Salazar 1997). The dry season lasts from April to November (INIA 1989;
Arroyo, Squeo et al. 1993; Fowler 1998). Daily rainfall shows a marked pattern, with most rain
falling in the afternoon. Soils are volcanic in origin, with low organic matter and saline content
(Aceituno 1993; Negrete 1993). However, in meadow areas, soils are rich in organic matter
and roots. Ground frost is frequent, and surface water freezes overnight during the dry
season (Baied and Wheeler 1993).
2.1.1
The Chilean altiplano
The Chilean section of the altiplano is characterised by plains grassland with steppe-type
plants and patches of meadow-like vegetation, surrounded by mountains. It is more arid and
less productive than the Peruvian altiplano. The total area of the Chilean altiplano is
approximately 1,760,000 ha (730,000 ha of flushing meadows or bofedales and 1,030,000 ha
of open dry grasslands) (Cattan 1993). The mean annual temperature is 5ºC at the
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Parinacota weather station, near the capture sites, which is at 4,390 m.a.s.l. (W 18 12’, S 69º
08’) (INIA 1989). July is the coldest month with a mean of -.04ºC, and January the warmest
(8ºC). The mean annual precipitation is 321 mm for the Parinacota Province and 200-250 mm
for the Surire basin and lies within the precipitation range for the whole region (Table 2.1) The
Surire basin is where the capture sites were located.
The rain gradient affects floral biodiversity with fewer genera and species per genus in the
drier regions of the altiplano (southern altiplano in Argentina and Chile) (Arroyo, Squeo et al.
1993). Plant species’ endemism in the study region averages 14% from 865 species that
inhabit Chile (Arroyo, Squeo et al. 1993). Four vegetation belts can be distinguished along the
Northern Chilean Andes (Arroyo, Squeo et al. 1993):
1.
pre-alpine belt (also called pre-puna or desert belt) located between 2,700 and 3,150 m;
2.
sub Andean belt (also called puna belt) between 3,150-3,850 m;
3.
low Andean belt (cushion belt) and
4.
high Andean belt beyond 3,850 to the vegetation line.
The vicuña lives in the high Andean belt where the dominant vegetation is characterised by
tussocks of grasses such as Festuca spp., Stipa deyeuxia and Oxychloe spp.. Patches of
vegetation more typical of the low Andean belts are also common within vicuña habitat.
Groundwater from melting ice creates local moist edaphic conditions (bofedales), where
hardy grass species grow abundantly (Rabinovics, Capurro et al. 1991). The dominant
grasses are members of the genera Festuca, Stipa and Hordeum . Bofedales are
permanently wet and located near streams, ponds or lakes, with a continuously green cover
of small herbs, rushes and grasses (Cattan and Glade 1989). They are characterised by
high vegetation cover (50-100%) with xerophytic species that have adapted to the extreme
climatic conditions of the puna. Herbaceous plants cover up to 37% of the bofedales.
Bofedales have been described as being composed of 24 plant associations of 16 different
species of bushes and grasses (Arroyo, Squeo et al. 1993). The dominant association is
Oxychloe andina usually combined with Werneria pygme, Werneria pinafitida, Dystlchia
muscoides and Gentlana prostata. The drier areas are dominated by sparse grassland,
primarily Deyeuxia and Festuca sp. Bushes present in the wet-dry ecotone are mainly
Parastephia quadrangularis and Parastrephia lepydophylla.
Total mean biomass (kg/ha ±SD) for Oxychloe andina fluctuates from 3,250±367 (sites
inundated only during the rainy season) to an intermediate level of 5,800±556 (sites
inundated most of the year, except the dry season) and a maximum productivity of 7,000±486
(sites inundated all year) (Muhlhauser 1993).
The altiplano holds 34% of the total fauna species of Chile. This includes 84 bird, 5
amphibian, 3 reptile and 20 mammal species. Only 19.6% of the taxa are threatened in
comparison with the mean threatened level of 33.6% for the whole country (Cattan 1993).
According to annual records of the Animal Health Office, populations of domestic stock in the
study area were approximately 31,000 alpaca, 41,000 llama and 31,000 sheep during the
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period of this study (Galaz, 1998). An estimated carrying capacity of 20 vicuña/km /year has
been suggested for the altiplano. Rabinovics et al. (1991) estimated carrying capacity at 7.6 2
7.9 vicuña/km for the Laguna Blanca reserve in Argentina, where mean annual precipitation
was 130 mm. Hoffmann, Otte et al. 1983 described a population decline from a density of 7.5
2
vicuña/km in Pampa Galeras, where the mean annual precipitation was 463 mm. It seems
that there is no clear consensus about the estimated carrying capacity of the altiplano for
vicuña and other species of South American Camelids.
Table 2.3. Annual rainfall (mm) in the study area between 1975 and 1986.
YEARS
JAN
FEB
MAR
APR MAY JUN JUL AUG SEP OCT NOV DEC
TOTAL/
YEAR
1975
152.8 110.2
-
-
-
-
-
-
-
-
-
77.9
340.9
1976
133.0 84.0
100.0
9.0
-
-
5.0
-
8.0
5.0
-
13.2
357.2
1977
84.0 147.0 140.0
-
-
-
-
-
3.0
-
1978
264.0 20.0
1979
57.0
5.0
-
-
-
-
-
6.0
135.0 42.5
88.0
-
-
-
-
-
-
-
-
23.0
288.5
1980
30.0
149.0
-
-
-
2.0
-
-
41.0
-
16.0
301.0
1981
187.0 226.0
66.0
21.0
-
-
-
16.0
14.0
-
2.0
48.0
580.0
1982
146.0 97.0
62.0
2.0
-
-
-
-
6.0
10.5
385.4
21.0
-
-
-
-
2.0
7.0
11.0
71.5
-
462.0
1983
6.0
63.0
24.5
-
142.5 127.5
86.0
2.0
3.0
-
-
5.0
-
1985
42.5 200.0
89.0
39.0
-
6.0
-
-
2.0
-
1986
75.5
120.0
15.5
-
.
-
18.0
-
-
MEAN/
116.5 102.3
88.9
13.4
3.0
6.0
3.5
10.3
6.7
78.0
32.0 108.0
30.5 31.4
1984
85.8
24.0
-
28.0 68.0
84.5 141.0
.
22.1 40.3
52.7
396.2
captivity.
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Maximum temperature ( Celsius)
Season
Mean
Std. Deviation
N
Mean
Std. Deviation
n
Nov-98
-3.9
3.3
52
19.3
2.8
48
Apr-95
-7.5
2.5
20
12.6
3.2
20
Mean
-4.9
3.5
72
17.3
4.2
68
Note: Significant differences between seasons for minimum (F1,70=18.69; p<0.001) and
maximum temperatures (F 1,66=75.08; p<0.001).
604.0
.
Table 2.4. Daily minimum and maximum environmental temperatures during studies in
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492.0
.
YEAR
Minimum temperature ( Celsius)
476.0