Fjölrit RALA - 05.12.1999, Síða 55

OSVALDG A. FERNÁNDEZEl AL.
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Etchevehere (1971) as Haplargids and Plaeorthids; dunes and extensive colluvial-
alluvial accumulations with salty soils are also common.
The climate of the Puna is very harsh. It is characterized by precipitation under 200
mm yr 1 which is concentrated in a wet summer season, high insolation and wide daily
temperature amplitudes. The mean annual temperature is mostly under 10°C, and
night temperatures below 0°C occur daily during the whole year. Snowfall is on aver-
age less than 5 days per year. The mean annual potential evapo-transpiration ranges
frorn 500 to 600 mm.
The flora and ecology of the Puna have been reported by Cabrera (1957, 1968). A
detailed study on the distribution, morphology and phenology of 115 species of this
region and the Pre-Puna mountain belt has also been prepared by Ruthsatz (1974). The
vegetation of the Puna is very closely related to that of Patagonia. Many of the domi-
nant genera are frequent in both regions such us Junellia, Fabiana, Chuquiraga,
Nardophyllum, Adesmia and Mulinum. Few of the Puna’s genera are not present in
Patagonia (Cabrera 1976). The predominant life forms are nanophanerophytes of 0.3
to 1.0 m high. The climax community is widely represented by a steppe rich in
shrubby species leaving wide soil spaces among them. Dominant shrubs are Fabiana
densa, Adesmia horriduscula and Baccharis boliviensis. Others species frequently
found are Adesmia spinossima, Junellia seriphioides, Baccharis incarum, Senecio
viridis, Acantholippia hastulata, Ephedra breana, Tetraglochin cristatus, etc. A few
cactuses are present such as Opuntia soehrendsii and Tepherocactus atacamensis. The
herbaceous cover is sparse and only partially covers the soils. The most frequent grass
species are Stipa cespitosa and S. leptostachya. Other herbaceous species representing
the local flora mainly during the rainy season are Mutisia friesiana, M. hamata,
Paraonichia cabrerae, Mitracarpus brevis, Hoffmanseggia gracilis, Conyza deserti-
cola, Portulaca perennis, P. rotundifolia, and Dichondra argentea. Atriplex micro-
phylla becomes dominant in salty plains reaching 0.3 to 0.4 m height. Baccharis
caespitosa, Distichlis humilis, Festuca hypsophila and Triglochin maritima are com-
monly found at the border of salty flats (Cabrera 1976).
Grazing by livestock such as goats, sheep, llamas (Lama glama), donkeys and cat-
tle is the principal economical activity in the Puna. Land cultivation is limited to small
areas of corn and quinoa (Chenopodium quinoa). About 25% of the shrubs are valu-
able as fodder plants. Some of the more palatable species are Ephedra breana, E. ru-
pestris, Krameria iluca, Buddleja hieronimy and Acantholippia hastulata which are
the target of intensive browsing (Ruthsatz 1974). The poorly regulated domestic live-
stock grazing has had adverse impact on the natural ecosystem. Some areas are mark-
edly deteriorated by the loss of vegetation cover, disappearance of desirable species,
and soil erosion.
Discussion and future research needs
A detailed map of utilization of the Argentinean rangelands will show that only the
non-accessible areas are free from anthropogenic perturbation. A large part of the
grazing industry depends on natural ecosystems for food. Most of these regions have
only a thin soil or are either rugged, too dry or sparsely vegetated for practical inten-
sive or abusive economical utilization. Direct perception of degradation of this system
occurs through a number of stages which frequently are not noted at a local or re-