IFEVA   02662
INSTITUTO DE INVESTIGACIONES FISIOLOGICAS Y ECOLOGICAS VINCULADAS A LA AGRICULTURA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Model up-scaling for assessment of sustainable management from Patagonian rangelands: the dilemma of continuous or rotational grazing.
Autor/es:
CIPRIOTTI, P.A.; WIEGAND, T.; PUETZ, S.; PARUELO, J.M.; IRISARRI, G.J.; BARTOLONI, N.; AGUIAR, M.R.
Lugar:
Rosario, Argentina
Reunión:
Congreso; IX International Rangeland Congress.; 2011
Resumen:
Degradation resulting from various factors, including non-sustainable grazing management, affects as much as 3.6 billion hectares of rangelands worldwide and reduces their ability to provide ecosystem services (Reynolds, 2007). Therefore, there is an urgent need to develop sustainable grazing managements to revert this impressive figure. However, developing an appropriate assessment of sustainable grazing management is inherently difficult for four major reasons: 1- a mismatch between time scales for observation and time scales of the vegetation change, 2- differences in the relevant spatial scales involved, 3- complex non-equilibrium rangeland dynamics, and 4- potential conflicts between resource conservation and production. Because of the complexity of the problem and the large time and spatial scales involved, modeling approaches are required. Here, we use model up scaling techniques to extend a small scale model (that captures effect of grazing and population dynamics on the scale of plants) to a model at the management relevant ranch scale with focus on vegetation. We use the upscaled model to evaluate the sustainability of alternative grazing managements at appropriate spatial and temporal scales in Patagonian rangelands. Three detailed vegetation models (< 1 ha) were up-scaled to large management-relevant scales (10,000 ha). The upscaling procedure is based on extensive simulations of the small scale models that describe the essential of vegetation dynamics for three vegetation communities (i.e. fescue grasslands, shrub-grass steppes, and wetland prairies) typical of Patagonian ranches in Argentina. The system dynamics was synthesized into a library of transition probability matrices among vegetation states for different environmental and grazing conditions. We also included a grazing sub-model to determine the punctual grazing intensity to cope with the vegetation and grazing heterogeneity, and the management decisions at paddock- or ranch-level. To characterize the real landscape heterogeneity of ranches, vegetation maps from this region were adapted to the model scale. Finally, extensive simulation experiments for real-like ranches with the up-scaled model (RANCH) were conducted to evaluate the ecological sustainability of alternative grazing managements by combining four stocking rates (0.1, 0.2, 0.3, and 0.4 AU/ha) under continuous or rotational (grazed area: 50, 33, 25, 16 %) grazing at long-term (200 years) for the current climate conditions of Patagonia. Under higher stocking rates (> 0.3 AU/ha) rotational grazing (16-25%) improved the vegetation condition more than a 75% respect to the continuous grazing. But at the lowest stocking rates the responses inverted and continuous grazing was better. However, the highest punctual stocking rates reached under rotational grazing could constrain the animal performance. From field studies there is not sufficient evidence to sustain that rotational grazing is better than continuous grazing (Briske et al., 2008). However, most of these conclusions are based on short-term studies (< 5 years) and/or small experimental plots (but see Teague & Dowhower, 2003; Jacobo et al., 2006). The effectiveness of rotational grazing to reduce rangeland degradation at long-term and ranch-level depends on the animal stocking rate in a non-lineal way.