Matriz del paisaje, escalas e interacciones en los sistemas silvopastoriles y agroforestales = Landscape matrix, scales and interactions in silvopastoral and agroforestry systems

Abstract

Los Sistemas Silvopastoriles (SSP) brindan una serie de beneficios ambientales y economicos respecto de las monoculturas agrícolas. En general se han abordado a nivel predial, asiladamente del paisaje que los contiene con el cual intercambian materiales, energía e información. Para analizar su papel en el nivel regional, es necesario comprender conceptos de ecología del paisaje y reconocer sus componentes y sus procesos. En este articulo se comentan estos elementos y se discuten la ubicación de los SSP y otros sistemas agroforestales, que simplificadamente pueden localizarse en: (i) Paisajes predominantemente boscosos, (ii) agroecosistemas, (iii) áreas de transición entres bosques y otras regiones sin bosques, ya sea en bordes naturales o de avance agropecuario.

Silvopastoral systems (SPS) provide a series of environmental and economic benefits with respect to agricultural monocultures. In general, they have been addressed at the farm level, in isolation from the landscape that contains them, with which they exchange materials, energy and information. To analyze its role at the regional level it is necessary to understand concepts of landscape ecology and to recognize its components and related processes. This article considers these elements and debate about the location of SPS and other agroforestry systems, which can be located in: (i) predominant forest landscapes, (ii) agroecosystems, (iii) transition areas between forests and other regions without forests, either on natural borders or agricultural borders. SPS in native forest areas, historically affected by livestock and fires contribute to stop erosion and recover tree cover from degraded areas, restoring their connectivity and flows of matter and energy. In the agricultural regions, their greatest utility may reside in mitigating adverse environmental impacts of agriculture and urbanism, by means of recreating shelterbelts for some wild components -including biological pest controllers-, acting as a barrier against the drift of agrochemicals, or removing contaminants from the soil. In forest transition ecotones, they can restore the forest structure and the flows that might have been interrupted by degradation, as well as modify the edge/surface ratio of altered landscapes. Some functions that can be partially restored in any of these environments are underground connectivity, nutrient circulation, water balance, nitrogen fixation or tree regeneration, recovering biomass and biodiversity, and protecting the native elements of the matrix unable to live at their edges. For these and other positive effects to occur, SPS must be designed and managed in order to maintain a selective permeability that facilitates the flow of species or propagules, limiting the penetration of contaminating agents and the expansion of introduced species, and complementing those natural corridors that link local plant communities with other ecosystems and landscapes. In short, in order to evaluate the regional impact of the SPS, it is essential to look at multiple scales, which allows us to recognize ecosystem services for the common good beyond the private benefits they could provide.