3 research outputs found

    Alien plant species on roadsides of the northwestern Patagonian steppe (Argentina)

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    The introduction of alien species represents one of the greatest threats to biodiversity worldwide. Highway construction increases the dispersal and invasion of exotic plant species. This study examined the assembly process of the plant communities to determine whether the roadsides of the Patagonian steppe represent a reservoir and dispersal source of invasive exotic species. We analyzed the composition of exotic and native species and functional groups present in the established vegetation and seed banks of roadsides and reference areas nearby. The type of dispersal of exotic and native species at the roadsides was also evaluated. Total cover and that of exotic and native species was lower at the roadsides than in the reference areas; however, at the roadsides the cover and seed abundance of exotic species was higher than that of native species. In the roadsides vegetation, native shrubs such as Acaena splendens predominated, along with exotic perennial herbs and grasses which were mainly represented by Rumex acetosella. In the seed bank the predominant species were exotic perennial herbs, also represented by R. acetosella, annual exotic species such as Epilobium brachycarpum and Verbascum thapsus, and annual native species such as Heliotropium paronychioides. No exotic shrubs were found either at the roadsides or in the reference areas. The species at the roadsides did not present a dominant type of dispersal. The abundance of exotic species at the roadsides, both in the aboveground vegetation and the seed bank, may be due to the stressful environment and the characteristics of the species themselves, such as the ability to form seed banks. This work revealed that the roadsides of the Patagonian steppe constitute reservoirs of invasive exotic species, highlighting the importance of identifying them and controlling their spread, with a view to generating ecosystem management programs.Fil: Chichizola, Giselle Ailin. Universidad Nacional del Comahue. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina.Fil: Chichizola, Giselle Ailin. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio Ecotono; Argentina.Fil: Chichizola, Giselle Ailin. Consejo Nacional de Investigaciones Cient铆ficas y T茅cnicas; Argentina.Fil: Gonzalez, Sof铆a Laura. Universidad Nacional del Comahue. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina.Fil: Gonzalez, Sof铆a Laura. Centro Regional Universitario Bariloche. Laboratorio Ecotono; Argentina.Fil: Gonzalez, Sof铆a Laura. Consejo Nacional de Investigaciones Cient铆ficas y T茅cnicas; Argentina.Fil: Rovere, Adiana. Universidad Nacional del Comahue. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina.Fil: Rovere, Adiana. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio Ecotono; Argentina.Fil: Rovere, Adiana. Consejo Nacional de Investigaciones Cient铆ficas y T茅cnicas; Argentina

    Requerimientos pregerminativos de Maihuenia patagonica y Maihueniopsis darwinii, cact谩ceas end茅micas de Patagonia

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    Cacti are characteristic plants in arid ecosystems, where they play an important ecological role. Many species are threatened because of habitat destruction and collection for commercial purposes. In South America, Argentina is one of the countries with the greatest cacti richness and endemisms. However, cacti have been scarcely studied, especially the southernmost species. Since the study of cacti鈥檚 reproductive biology would help to improve their conservation status, we studied basic physiological aspects of the germination of two endemic species of Argentina and Chile, Maihuenia patagonica (Phil.) Britton & Rose and Maihueniopsis darwinii (Hensl.) F. Ritter var. hickenii (Britton & Rose) R. Kiesling. Germination percentage (G), mean germination time (TMG) and time until germination (IG) of control seeds and seeds subjected to three pre-germinative treatments were evaluated. Treatments were cold moist stratification for 40 days, mechanical scarification with sand and sandpaper, and mechanical scarification with a scalpel. Laboratory assays were performed at 20/10 掳C and 12 h light/12 h dark regime during 60 days. In M. patagonica germination in the stratification treatment did not differ from the control, but was higher in the scarification with scalpel. In M. darwinii var. hickenii germination only differed between the stratification and the scarification with scalpel. TMG and IG were higher in the stratification treatment than in the control for M. patagonica, whereas scarification treatments did not differ from the control. As for M. darwinii var. hickenii no differences were detected for TMG, but the IG was lower in the stratification than in the control. Probably both species presents some kind of dormancy, since germination percentages were low (M. patagonica between 8-27 % and M. darwinii var. hickenii between 17-26 %) but seeds presented high viability. Presence of physical dormancy is discarded because control seeds of both species germinated and the presence of non deep physiological dormancy is proposed. The latter was partially overcome by mechanical scarification in M. patagonica. These results are a new contribution to the study of cacti in South America and could help to develop in situ conservation strategies through the restoration of degraded areas.Las cact谩ceas son plantas caracter铆sticas de ecosistemas 谩ridos, en los cuales desarrollan un importante papel ecol贸gico. Se encuentran amenazadas por la destrucci贸n del h谩bitat y la extracci贸n con fines comerciales. Argentina es uno de los pa铆ses de Sudam茅rica con mayor riqueza y nivel de endemismo de cact谩ceas, sin embargo, su estudio es escaso, especialmente para las especies de distribuci贸n m谩s austral. Dado que un mayor conocimiento sobre la biolog铆a reproductiva de los cactus ayudar铆a a mejorar su conservaci贸n, se estudiaron aspectos fisiol贸gicos b谩sicos sobre la germinaci贸n de dos especies end茅micas de Argentina y Chile, Maihuenia patagonica (Phil.) Britton & Rose y Maihueniopsis darwinii (Hensl.) F. Ritter var. hickenii (Britton & Rose) R. Kiesling. Se evalu贸 el porcentaje de germinaci贸n (G), el tiempo medio de germinaci贸n (TMG) y los d铆as transcurridos hasta el inicio de la germinaci贸n (IG) de un control y de tres tratamientos pre-germinativos: estratificaci贸n h煤meda fr铆a, escarificaci贸n mec谩nica con lija y arena, y escarificaci贸n mec谩nica con bistur铆. El ensayo se extendi贸 por 60 d铆as, en c谩mara de germinaci贸n a 20/10 掳C, 12 h luz/12 h oscuridad. Para M. patagonica la germinaci贸n no difiri贸 entre la estratificaci贸n y el control, pero fue mayor al control en la escarificaci贸n con bistur铆. Para M. darwinii var. hickenii la germinaci贸n s贸lo difiri贸 entre la estratificaci贸n y la escarificaci贸n con bistur铆. El TMG y el IG fueron mayores para la estratificaci贸n que para el control en M. patagonica, mientras que los tratamientos de escarificaci贸n no difirieron del control. En el caso de M. darwinii var. hickenii no se observaron diferencias en el TMG, pero el IG fue menor en la estratificaci贸n que en el control. Es posible que ambas especies presenten alg煤n tipo de dormancia, ya que los porcentajes de germinaci贸n fueron bajos (M. patagonica de 8-27 % y M. darwinii var. hickenii de 17-26 %), pero las semillas presentaron elevada viabilidad. Se descarta la existencia de dormancia f铆sica debido a que hubo germinaci贸n en el control de ambas especies y se propone la existencia de dormancia fisiol贸gica leve, la cual habr铆a sido superada parcialmente por la escarificaci贸n mec谩nica con bistur铆 del tegumento en M. patagonica. Los resultados obtenidos constituyen un nuevo aporte al estudio de las cact谩ceas de Sudam茅rica, que puede ser utilizado para el desarrollo de medidas de conservaci贸n in situ mediante la restauraci贸n de h谩bitats naturales degradados
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