Emergence and Seedling Survival of Calden in the Semiarid Region of Argentina

Abstract

CaldLn (Prosopis cd&n& Burk.) is one of the woody species that is increasiag in abundance due to poor grazing management in the semiarid region of central Argentina. The objectives of this work were to evaluate emergence and seedling survival of caldkn under grazed-low herbaceous follar cover, and ungrazed-intermediate and ungrued-high herbaceous follar cover. Seedling emergence was recorded weekly after 3 plantig dates: October 1987, September 1988, and October 1989. SeedUng survival was recorded every 2 weeks until all seedlings died. Precipitation, soil water potential, and soil temperature were monitored during the study period. Since caldLn only reproduces from seeds, optimal conditions for gennlnation under different controlled photoperlod and temperature regimes were also studied. In the laboratory, greatest germination of freshly harvested unscarifled seeds occurred at a diurnally alternating temperature regime of 15 and 300 C with light provided for 9 hours. Least germination occurred at 150 C and continuous darkness. Acid scarlficatlon significantly increased germination percentage and germination rate. Unscarified seeds incubated in light exhibited a lower rate of germination than scarified seeds under all temperatures. In the field, soil water availability was usually similar among the 3 experimental conditions. Soil temperature was only occasionally higher in the grazedlow herbaceous cover site. Only for 1987 data, emergence was greater on the grazed area with relatively low herbaceous follar cover and similar within the ungrazed area. Treatment effect was very little on seedling survival, being lower in the grazed area for only 2 evaluation dates in 1989. Regardless of treatment the emerged seedlings survived 40 days on the average. The highest caldbn seedling mortality was always coincident with higher soil temperature and lower soil water availability.

Germination in Prosopis ferox seeds: effects of mechanical, chemical and biological scarificators

“…Pela´ez et al (1992), recorded high germination rates treating Prosopis caldenia seeds with sulphuric acid, but they used longer exposition time (45 min). It is important to emphasize that unlike other species of the genus Prosopis, germination was not obtained without seed scarification.…”

“…Some researches about the factors influencing recruitment in the genus suggest that both, germination and establishment are enhanced by cattle dispersal (Pela´ez et al, 1992;Cox et al, 1993), assigning to the animals the scarifying agent role. This is based on the fact that the seeds that pass through the digestive tracts could be liberated from physical dormancy.…”

Effect of high temperatures on seed germination of Prosopis caldenia Burk

“…(Leguminosae) is a thorny deciduous perennial woody species native of the temperate semi-arid phytogeographic region of central Argentina known as the Caldén District (Cabrera, 1976). Its abundance increased after the introduction of domestic livestock, being at present one of the dominant woody species in the region (Peláez et al, 1992). Prosopis species have an indehiscent legume fruit split into segments.…”

“…Prosopis caldenia only reproduces from seeds (Cabrera, 1967). Prosopis caldenia seeds exhibit a degree of innate dormancy like other members of the genus Prosopis (Peláez et al, 1992;Peinetti et al, 1993).…”

Seed Germination Characteristics ofRhus tripartitum(Ucria) Grande andZiziphus lotus(L.): Effects of Water Stress

“…However, the establishment of these woody species would be possible only after years of above normal and well-distributed rainfall [31].…”