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Observatorio Astronómico de Ampimpa

by Carina Kozmich and Hannah Perlinger

Climate and vegetation of the Eastern Cordillera Map
General information

The western slopes of the Eastern Cordillera, heading towards the Valle Santa María, are well protected against the humid air masses pushing towards the eastern margin of the Andes. They represent an open semi-desert landscape with columnar cacti of impressive height, storing a considerable amount of water in their stems. A closer look, however, reveals several more strategies which are used by plants to survive with limited water supply. These can be well observed at the otherwise inconspicious Observatorio Astronómico de Ampimpa along the road between Amaicha del Valle and the Paso El Infernillo. It is not by chance that this area is known as Los Cardones, the Spanish term for columnar cactus: the many tall individuals of Echinopsis terscheckii immediately catch the travellers' eyes.

The art of survival in the desert

Thorn shrub semi-deserts are characterized by amounts of 125 mm to 250 mm of precipitation each year, whereas the rest of the time remains dry. Plants have developed various adaptation strategies to cope with these harsh conditions.

Try to identify these strategies, using the images and the points mentioned below.

  1. Describe the photographs.
  2. Which adaptation strategies belong to which plant? It is possible that the same plant uses more than one of the strategies.
  3. Which plant, do you think, uses the most strategies to survive in arid regions?

Click the corresponding check boxes. The number above each box refers to the number of the photograph.

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Click on the arrows or into the image and learn more about how plants adapt to dry habitats.

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These photos were taken at various locations in western Argentina. All features shown can be well observed also at the present point of interest.

Smaller surface: smaller leaf surfaces mean less loss of water (less transpiration through the leaves of the plants). In order to compensate the reduced leaf area, some plans incorpoate chlorophyll in their woody parts such as stems and branches.

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Thorns: like small leaves, they have a small surface and therefore avoid extensive loss of water through transpiration. They further protect the plant from herbivorous animals.

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Root system: The distance to neighbouring plants is essential for the availability of water. If the distance is larger, the plant has a higher chance to compensate low precipitation by the expansion of its root system. A sparse vegetation cover in arid regions indicates a a dense root network. Root competition for water is high in such cases. Some plants even let their roots grow into the underground deep enough for reaching the groundwater.

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Thick leaves or stems (succulence): this indicates the ability of plants to store water in their stems or leaves. These plants are known as succulents. Their stems or leaves are much thicker than those of other plants.

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Avoidance of drought: ephemerous (short-lived) plants can completely avoid dry periods by surviving beneath the soil surface. These plants endure dry periods as seeds, bulbs, or tubers beneath the surface and form stipes, leaves, and flowers only in times with sufficient water supply. Their strategy consists in the ability to complete growth and reproduction within short, favourable periods (often only 1-2 months).

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Show solution

As we can see, the cactus has developed most adaptation strategies to survive in arid areas.

Cacti have a horizontally extensive, but shallow root system. So, they can very well use the infiltrating water and direct it into their stems. Cacti have succulent stems, meaning that their stems consist of individial folds of tissue which can extend - comparable to an accordion - in order to store water, and contract in dry periods when the cactus uses up the stored water. Furthermore, a thick leathery surface protects the catus from transpiring too much water. In addition, leaves have evolved to thorns over time, in order to reduce the transpiring surface and to reduce the loss of water as much as possible. The large stem surface, with built-in chlorophyll, takes over the duties of the leaves such as photosynthesis.

A very old and impressive individual of Echinopsis terscheckii stands directly beside the observatory.

Adaptation to water scarcity hardly plays any role on the other side of the Paso del Infernillo, as you can see at the point of interest Virgen de las Flores.

References and links

Blümel, W.D. (2013): Wüsten. Stuttgart: Verlag Eugen Ulmer KG

Welt der Wunder (2015): Grüne Survival-Profis: Wie überleben Kakteen in der Wüste? [Access source]

Schultz, J. (2016): Die Ökozonen der Erde. Stuttgart: Verlag Eugen Ulmer KG

Simply Science (2016): Welche Pflanzen wachsen in der Wüste? [Access source]

Wikipedia article on Echinopsis terscheckii [Access source]

This contribution was revised, extended, and translated from German by Martin Mergili.