Seasonal environmental variation and plant phenology in arid Patagonia (Argentina)

BERTILLER, MONICA B.; BEESKOW, ANA M.; CORONATO, FERNANDO

JOURNAL OF ARID ENVIRONMENTS

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Año: 1991 vol. 21 p. 1 - 11

0140-1963

The phenological development of the main plant components of an arid ecosystem of north-eastern Patagonia and their relationships with some environmental variables were investigated. Maximum and minimum air temperatures, precipitation, soil moisture (%) and (NO3-N) and (NH4-N) in the equilibrium solution at different soil depths were measured at weekly intervals. Thirteen phenological phases were described for each of the following species: Larrea divaricata, Chuquiraga avellanedae, Lycium chilense, Poa ligularis, Stipa speciosa, and Stipa tenuis. The depth of penetration of each species' root system was also measured. Two groups of species were identified based on the timing of the phenological events and the depth of the root systems. One group represented by L. chilense, P. ligularis, S. speciosa, and S. tenuis included shallow-rooted species. These exhibited biological activity early in the growing season (winter?late spring) in accordance with high soil moisture and high (NO3-N) in the upper soil (0?0·8m). The other group consisted of L. divaricata and C. avellanedae, which are deep-rooted species. Phenology in these species progressed during the dry period (summer-late summer) when soil moisture and (NO3-N) in the upper soil were depleted and the deep soil (0·9m or more) maintained high values of soil moisture and high (NO3-N). As in other arid ecosystems, plant species of north-eastern Patagonia showed phenological asynchrony among species in accordance with the ability of each species to exploit water and nutrients stored in different soil sub-spaces.