U. Karlin

Effects of salinity on germination and seedling growth of Prosopis flexuosa (D.C.)

Abstract Prosopis flexuosa, the most widespread arboreal legume found on saline soils in Argentina, is regarded as an especially attractive species for the productive recovery of arid and salt-affected areas. The effects of salinity on germination and seedling growth of this species were studied. Salt tolerance during germination was examined in seeds collected from two populations growing either on saline or non-saline soil. Germination was assessed under various NaCl concentrations: 0, 0.2, 0.4, 0.6 and 0.8 M. Significant decreases in germination percentage were observed above 0.2 M NaCl. Variability was higher among individual trees than between populations and highest at 0.4 M NaCl. Salt tolerance at the seedling stage was analysed in 20-day-old seedlings, grown in pots with soil, treated for 90 days with NaCl solutions ranging between 0 and 0.4 M. The average seedling survival percentage for the trial was above 96%. A 50% decrease in final height was observed in the treatment with 0.4 M NaCl, where substrate in the pots had reached a final salt concentration of nearly 1 M NaCl. In Prosopis flexuosa, salt tolerance at the seedling stage appears to be greater than at the germination stage, suggesting that seedlings could be used for afforestation of salt-affected areas.

Experimental study on survival rates in two arboreal species from the Argentinean Dry Chaco

Abstract Given the state of resource degradation encountered in Chaco (Argentina), research on forest recovery methods and management proposals in accordance with the socioeconomic conditions of the regions inhabitants are imperative. The evaluation of factors that affect the plantation of arboreal species and the management knowledge necessary in the initial afforestation of highly degraded production systems are important elements in the plan for recovery. The present study investigates the importance of the factors: the effect of shrubs, grazing and native species to be planted on the success of afforestation in areas characterized by a high degree of resource degradation. Its objectives are to evaluate the role of Larrea divaricata ‘jarilla’ in the survival of Prosopis chilensis (Mol.) Stuntz and Aspidosperma quebracho blanco, and the effects of attenuated levels of domestic grazing on the survival rate of P. chilensis afforestation in real production units. Four areas located in old beds left by the Chancani River, reflecting the degraded soil and forest conditions, were set up as real production units. The vegetation community at each site contained 70% L. divaricata, the dominant species. Prosopis flexuosa D.C. and emergent A. quebracho blanco (quebracho) comprised the arboreal stratum. Experimentally planted quebracho and mesquite seedlings survival rates differed with respect to the shrub-effect. Shrubs were not found to exert any facilitating effect on the survival rate in mesquite, indicating that mesquite would have a higher survival rate in open spaces. However, shrub presence was found to be somewhat beneficial to survival in quebracho one year after the beginning of the trial. Herbivores with and without shrubs were a significant factor decreasing survival in P. chilensis.

Afforestation trials with Prosopis chilensis (Mol.) Stuntz and Prosopis flexuosa D.C. in the Dry Chaco, Argentina

Abstract In implantation trials carried out with Prosopis chilensis and Prosopis flexuosa, the following variables were considered: implantation time (December and March), implantation technique (direct seeding and seedling transplantation) and age of the seedlings at the time of transplantation (60, 105 and 150 days). Survival was evaluated for more than 9 months after implantation and trials were repeated in 3 consecutive years. Results from both species were similar and they show that survival after transplantation was higher (60–80%) than from direct seeding (35–45%). Survival from transplantation was independent of the size and age of the seedlings and it was less affected by climatic conditions than direct field sowing. Survival from direct seeding was higher in March than in December. The best time for either implantation alternative would be the end of the summer or beginning of fall, when climatic conditions increase the probability of seedling survival.

Caracterización florística de la Reserva Natural Militar Estancia La Calera

Las Sierras de Cordoba experimentan en la actualidad transformaciones causadas por el avance inmobiliario, incendios, tala, sobrepastoreo e invasion de especies exoticas. Estas transformaciones condicionan el estado de conservacion de la flora nativa. La Reserva Militar Natural La Calera, ubicada en las Sierras de Cordoba, ha mantenido gran parte de su estructura vegetal original como consecuencia de las restricciones al ingreso debido al uso militar. El presente trabajo muestra los resultados de las actividades de diagnostico floristico llevados a cabo en esta area de 14 mil hectareas durante 2012 y 2013. Se realizo una clasificacion ISO Cluster, como base para los relevamientos floristicos realizados a traves del Metodo Fitosociologico de Braun Blanquet. Se calcularon los Indices de Biodiversidad de Shannon-Weaver y se determinaron las especies caracteristicas de cada ambiente, basados en los valores de abundancia y dominancia. A traves de un analisis discriminante se determinaron las clases de vegetacion, las cuales permitieron definir las mismas en una clasificacion supervisada. Fueron identificadas 230 especies, de las cuales el 8,3% son exoticas, valor inferior a la proporcion de exoticas encontradas para el total de las Sierras de Cordoba. Estas especies exoticas se restringen a zonas riparias. El 17,0% del total de especies relevado son endemicas de la ecorregion Chaquena, lo que hace de esta Reserva un lugar de alto valor de conservacion. Seis comunidades vegetales fueron identificadas, representadas en cuatro clases de vegetacion en la clasificacion supervisada.