Since its introduction in the 1950s, tall fescue has spread throughout the Pampas region of Argentina to become naturalized in much of this region. Its annual forage mass productivity shows significant differences among sites. In this work, we hypothesized that, under dryland conditions, the annual forage mass productivity is related to the probability that the corresponding site is within the ecological niche of the species. To test this hypothesis, the spontaneous occurrence of tall fescue was surveyed in an area of 440 000 km2. The abundance of tall fescue was verified on roadsides of national and provincial roads, in systematic sampling points spaced every 50 km. Subsequently, the ecological niche of the species was estimated with the Maxent software, based on the environmental information available. Additionally, the bioclimatic variables with greatest influence in determining the ecological niche were identified. Based on the information of comparative yield trials of tall fescue cultivars, a correlation analysis between annual forage mass productivity and the likelihood of ecological niche was performed. We found that the realized ecological niche of tall fescue in the Pampas region covers an area of 237 000 km2 where the average minimum temperature of the coldest month is between 2·6 and 3·2°C and the rainfall in the driest quarter is 100 mm or higher. We also found that there were significant correlations between annual forage mass productivity and the probability of realized ecological niche. Therefore, in areas with low probability of realized ecological niche, other forage species could be a better option than tall fescue to obtain a high and stable annual forage mass productivity.

If technologies for decentralised sanitation and reuse (DESAR) and for natural stormwater management should at least partially replace existing systems, then intensive reconstruction work becomes essential. A conversion can only be realised successively over a long period due to high construction and financial expenses and requires new strategies. This paper presents the development and practical implementation of a mathematical tool to find an optimised strategy for the realisation of alternative and more decentralised drainage and sanitation concepts in existing urban areas. The succession of construction measures (e.g. the implementation of decentralised greywater recycling) for the whole period of consideration is determined based upon a mathematical optimisation model on the condition that the favoured future state is known. The model describes the complex interdependencies of the urban water and nutrient cycle and enables the minimisation of both financial efforts and ecological impacts on the way toward the future state. The results of the implementation for a rural area in Germany show that the mathematical optimisation is an adequate instrument to support decision-making processes in finding strategies for the realisation of sustainable urban water management.

Se analizó el efecto del pastoreo y descansos sobre la riqueza florística, la producción de materia seca y la cobertura de un pastizal degradado en el Delta del Paraná. El estudio abarcó 13 meses, divido en un primer sub-período con tres tratamientos: pastoreo continuo con alta carga (desde 1 equivalente vaca/ha), clausura con cortes bimestrales de la vegetación y clausura sin cortes, y segundo sub-período con: anegamiento y sin clausuras. Los datos de vegetación se analizaron mediantes métodos multivariados (análisis de componentes principales). Según los resultados, en contraposición al pastoreo continuo, con descansos de dos meses se cubrió totalmente el suelo, se registró un incremento en la riqueza florística nativa, aparecieron especies forrajeras de crecimiento primavero- estivo- otoñal y en una estación de crecimiento mejoró la oferta de materia seca. Es posible favorecer valores de las variables estudiadas del pastizal y mejorar la oferta forrajera con un manejo adecuado.