Nature Around the ALMA Site – Part 2

Astronomical News Nature Around the ALMA Site – Part 2 Figure 1: The vegetation Michel Grenon Valeriana nivalis belts as described (Geneva Observatory, Switzerland) Festuca chrysophylla Mulinum crassifolium m by Richter (2003) on the Adesmia spinosissima Deyeuxia curvala slopes of Sairecabur Baccharis tola Pycnophyllum bryo 5 500 volcano, NW of ALMA, The natural environment around the Parastrephia quadrangularis with indication of char- oVg ALMA site, its flora, fauna and land- Fabiana denudata 5000 acteristic plants. scape morphology, are presented and Junellia seriphioides interpreted in terms of combined geo- Trichocereus atacamensis 4500 logical and climatic evolution with, in Atriplex imbricata parallel, the necessary biological adap- Opuntia camachoi 4 000 tions. This part covers vegetation and 3 500 animal life. uVg 3 000 Sairecabur The vegetation belts Figure 2: The Maihuen- The vegetation belts contain plant asso- iopsis pillows show the effect of the katabatic cations adapted to a given range of at- winds. The side exposed mospheric parameters, soil composition to the cold flow is red- and texture. A recent phytosociological der, an indication of a survey by Richter (2003) provides vege- higher content in antho- cyanine, a molecule tation transects in the ALMA area, namely acting as anti-freeze. at Sairecabur, Toco Toco and Miñiques (Figure 1). On the western slopes of Toco Toco, all belts are present, because the rocks are old enough to have been al- tered into sand and clay, and hence are able to retain water. At the lowest level, 2 900–3 350 m, the limiting factors are the scarcity of precip- itation, the high evapotranspiration and the salt and nitrate content in the soil. Atriplex communities – tall greyish bushes Figure 3: Thanks to the – develop on the shore of the Atacama reduction of the leaf size, Fabiana bryoides Salar in salt rich soils. On undisturbed resists dessicating rocky places, the cactus Maihueniopsis winds and may grow up camachoi forms colonies of spiny pillows to 4900 m. (Figure 2), among several other plants. In wind shadow places, the tall cactus Trichocereus atacamensis, an invader from Argentina, grows. At higher altitudes, evapotranspiration becomes the dominant factor. The effi- ciency of the evaporation increases with the square of the wind velocity. Low humidity and high wind velocity favour high rates of water loss by the plant epiderm. Several techniques are devel- oped by plants to reduce these losses. suppressed and photosynthesis takes In the zone 3 850–4 300 m, the vegeta- place at the upper stem surface. The tion becomes scarce and the grami- In the second vegetation zone, 3 350– whole plant is varnished with a viscous naceae herbs are dominant. The golden 3 850 m, is found Fabiana bryoides, resin. In other plants, such as some Festuca chrysophylla gives the landscape with leaves reduced to minute rosettes, Senecios, the water losses are minimised its colour and specific character (Figure 4). forming a compact cover on the stem, through the development of a white to- Behind the tufts of Festuca, in the wind mimicking coral branches (Figure 3). In mentum of dense crispy hairs, reflecting shadow, several plant species may de- the same zone, Fabiana denudata repre- the solar radiation and setting the wind velop. Parastrephia quadrangularis is an- sents an extreme case: its leaves are velocity to zero at the epiderm surface. other typical plant with leaves reduced The Messenger 128 – June 2007 57 Astronomical News Grenon M., Nature Around the ALMA Site – Part 2 to scales, covering the stem as tiles. The Figure 4: Festuca association of Festuca, Parastrephia and chrysophylla forms large populations giving a Baccharis provides the preferred pasture golden aspect to the of guanacos and vicuñas (Figure 5). landscape at altitudes where most bushes, ex- cept Parastrephia, have disappeared. The high-altitude vegetation In the zone 4 350 m to 4 850–5150 m, the wind intensity, the eolian erosion and the temperature are the limiting factors for vegetation. On flat surfaces, plants have to minimise their cross section with re- spect to the thermal and zonal winds. To expand horizontally is a frequently en- countered adaptation, e.g. by Pycno- phyllum bryoides (Figure 6) and by the Calyceras genus (Figure 7). This strategy is also adopted by some dwarf trees Figure 5: Vicuñas in as Adesmia sp., which develops an under- the altoandine steppe near Maricunga Salar, ground stem and branch systems ex- 3 800 m. tending well below the surface. Leaves are covered with hygroscopic glanduli- ferous hairs able to absorb directly the humidity from the air. In rocky places, plants may develop pro- vided the soil is evolved. Fresh lava or Figure 6 (below): lapilli cannot retain water close to the sur- Pycnophyllum bryoides face and several centuries of weathering expands as rings on are needed before the first plant colony flat gravel surfaces (left). Leaves are reduced may settle. On older substrates, such as to ovoid cones (right), at Toco Toco, plants use rock cracks, petals are translucid, at wind shadow, to expand their roots in and so the plant offers clay, searching for residual humidity. a minimum surface to dessicating winds. Nototriche holosericea and Chaetanthera revoluta (Figure 9), and Oxalis sp. (Fig- ure 10), are typical examples of this be- haviour. In small valleys oriented NS, perpendicu- lar to the afternoon and zonal winds, the soil and plant evaporation is notice- ably reduced. Snow may accumulate during winter and stay until the next blos- soming season. Plant communities re- quiring less protection against evapotranspiration may develop up to very high altitudes, as the Werneria-Senecio association, consisting of a dozen different species. Around ALMA, this association is characterised by the presence of Werneria poposa and Valeriana nivalis (Figure 11). In these sites, the limiting factor is the temperature, which reduces the duration of the vegetation period to nearly zero above 4850–4900 m. 58 The Messenger 128 – June 2007 Figure 8: This Adesmia sp. is an underground dwarf tree. Strong spines prevent grazing by viscachas or vicuñas (Toco Toco, 4 500 m). Figure 7 (above): In Figure 9 (below): In Nototriche holosericea (left) Calyceras genus, the leaves are undulated and cerebriform; the surface hemispherical head of available for gas exchanges exposed to the wind green flowers is the only is manyfold. A white indumentum protects the leaf part emerging above from transpiration and UV radiation. Chaetanthera ground level (Laguna revoluta flowers (right) open on top of 1 cm long Miscanti, 4000 m). cones, covered by hairy leaves (Llano de Pajonales, 4 410 m). Figure 10: This Oxalis sp. expands along narrow cracks, in sunny places, at Toco Toco, 4 400 m. The Messenger 128 – June 2007 59 Astronomical News Grenon M., Nature Around the ALMA Site – Part 2 Figure 11: Werneria poposa (left) grows in wet and wind-shadow rocky places, close to Valeriana nivalis Figure 13: Calceolaria stellariifolia is a rare plant (right), a rather common plant reaching the upper found between 4000 and 4300 m around ALMA. Its limit of the vegetation; its thick root is strongly aro- geographical distribution shows a typical area matic, reminiscent of the Celtic Nard (N of Toco disjunction consequent on the postglacial climate Toco, 4 520 m). warming. Figure 14: Senecio aff. algens grows between dark rocks exposed to the west. The altitude of Toco Toco station, at 5150 m, is the highest for flowering plants observed so far near ALMA. Figure 12: Four representative plants at the vege- ground), than on bright colours, in order tion limit. As a result, the areas occupied tation limit in humid places at Cerro Toco Toco. to attract hymenopter pollinators whose by high Andian plants are now disjunct. Top left: Calandrinia sp.; top right: Menonvillea sp. (4 820 m); lower left: Perezia atacamensis (4700 m); eyes, or ocelli, are sensitive down to An example of severe area restriction is lower right: Werneria pinnatifida (4700 m). UV-B radiation. that of Calceolaria stellariifolia (Figure 13), found in only half a dozen sites, spread The present geographical distribution of over 1500 km in the high Andes. When high Andes plants reflects the restric- isolated, plants may follow divergent ge- A notable character of the high-altitude tion of areas consequent on the climate netic evolution, they have no chance to flowers is the restriction of their colour warming after the Ice Age. Intermediate merge their genes again before the next range. They look unattractive to the altitude plant communities had to move glaciation. human eye: blue, orange, red colours are up by about 1 km, migrating towards no longer present. Most flowers are the altiplano on gentle slopes east of the Plants reaching the maximum altitude white, yellowish or at best bright yellow Atacama Desert core, or towards the around ALMA belong to the Senecio (Figure 12). With a very low ground top of isolated mountain ranges. Those genus. Senecio Puchii is frequently seen coverage, plants appear to rely more on already growing on the altiplano during up to 4750 m. Senecio aff. algens (Fig- petal UV-reflectivity, (increasing the con- the Ice Age are found presently on iso- ure 14), replaces it at higher altitude, in trast between the flowers and the lated peaks, close to the upper vegeta- sunny places between 4 850 and 5150 m. 60 The Messenger 128 – June 2007 Hot springs and high altitude vegas Figure 15: High andine vegas are formed of compact material, strong Wet biotopes are due either to hot springs enough to resist the in hydrothermal fields as at El Tatio, or weight of vicuñas or to the development of high altitude vegas, even llamas (Chungara, the southern counterpart of peat bog in 4 500 m).

Load more