Seedling emergence and survival in contrasting soil microsites in the Patagonian-Monte shrubland.

BISIGATO, A.J.; BERTILLER, M.B

JOURNAL OF VEGETATION SCIENCE

WILEY-BLACKWELL PUBLISHING, INC

Año: 1999 vol. 10 p. 335 - 342

1100-9233

The potential of two perennial species (Larreadivaricata and Stipa tenuis) to colonize different soil micrositeswas analyzed in the Patagonian Monte shrubland. We hypothesize that the short-lived grass S. tenuis is more able tocolonize the soil of microsites beneath vegetation patcheswhere N-fertility is higher than those in bare soil, while thelong-lived shrub L. divaricata colonizes different soil micrositesirrespective of their N fertility. A greenhouse experiment wascarried out to evaluate the emergence and survival of bothspecies in different soil microsites at different water, inorganicN and seed densities. In all cases soil microsites were seedlimited since the addition of viable seeds increased seedlingemergence. Both species showed, however, different abilitiesto emerge and survive in different soil microsites. Micrositesof bare soil were more favourable for seedling emergence andsurvival of L. divaricata than those beneath vegetation patches,independent of their water status. This ability of L. divaricatacan not be explained on the basis of increased water or Navailability, but probably because of lower salt content of baresoil. The addition of inorganic N reduced the survival of L.divaricata in both microsites but increased individual plantperformance. The emergence and survival of S. tenuis was notdifferent in both types of soil microsites but the addition ofinorganic N increased seedling emergence and plant biomass.According to these results, emergence and plant performanceof S. tenuis may be promoted during humid years by increasedconcentration of inorganic N. Since N mineralization occurs ata higher rate in soil microsites beneath vegetation patches thanin those of bare soil, higher plant performance and probablyestablishment of S. tenuis is to be expected. These results areconsistent with an existing conceptual model of plant dynamics under various grazing intensities in the Patagonian Monteshrubland based on previous field observations.