CONICET | Buscador de Institutos y Recursos Humanos

The present work studies the relationship between environmental heterogeneity and the vegetation of levee?s neo-ecosystems in the islands of the Lower Delta. These habitat types can be considered plant communities of relatively recent origin related to the local productive activities. Vegetation coverage was evaluated in ninety-seven plots of three different environmental units (A, B and C), using classification analysis, indirect and direct ordinations. Edaphic parameters and the hydrological regime were also analyzed. Unit A?s vegetation was different from that of units B and C, and was characterized by a dominant herbaceous species (Carrizo, Panicum grumosum) and similar vegetation in all the different types of neo-ecosystems. Despite having different local hydrological regimes, units B and C showed a similar response regarding the constitution of their vegetation. A high development of a group of alien species led to a convergence in the structure and composition of vegetation. In ?short term abandonment? neoecosystems two alien species predominated (Lonicera japonica and Rubus sp.), whereas in ?long or medium term abandonment? habitat types the dominant tree species were two alien (Chinese privet, Ligustrum sinense; green ash, Fraxinus pennsylvanica) and two native species (canelón, Rapanea sp. and anacahuita, Blepharocalyx tweediei). This differential response in the observed vegetation between the different environmental units Could be related to a greater fluvial influence of the Paraná River on unit A and a greater tidal influence of the de la Plata River on units B and C. Both classification and ordination analysis (whether direct or indirect) would agree in signaling the aforementioned relationship. The Lower Delta hydrological regimes affect only a number of edaphic parameters in neo-ecosystems, particularly pH, organic matter percentage and clay content. In conclusion, to understand the spatial pattern of neo-ecosystems? vegetation in levees of Lower Delta islands it is necessary to take into account not only the abiotic factors but also the invasion of alien species that has been taking place for over 50 years.

enviar mensaje