Abstract

The Patagonian landscape is in constant danger due to agricultural and/or livestock activities. This is due to the unsustainable management practices carried out by regional ranchers because of high input costs or a lack of knowledge regarding alternative, sustainable grazing techniques. It is therefore essential to manage this landscape in a way that permits production, as well as supporting the essential ecosystem services that it provides. It has thus been proposed that Vegas (wetland meadows) are potentially suitable zones for ecologically intense, site-specific management that could form part of continuous, sustainable animal management. In this context, the aims of this research were a) to relate the most relevant variables (soil-water-plant) in a Vega with its spatial variability and b) to define and characterize the different sectors, considering the parameters evaluated and their relationship with ecosystem functions and potential agricultural, livestock or environmental conservation uses in a Vega in the transition zone of the southern Chilean Patagonia. Therefore, the relevance of many variables associated with edaphic, hydric, vegetation and productive dynamics was evaluated with the Cos2 index; subsequently, their spatial dependence was determined using geostatistics. Each variable was evaluated in a grid system, where each point was georeferenced. Soil types were determined in 7 sectors of the Vega (northern summit, northern high footslope, northern low footslope, center of the Vega, southern low footslope, southern high footslope and southern summit). The most relevant variables were bulk density (BD), aluminum pyrophosphate (Alp), soil organic carbon (SOC), cation exchange capacity (CEC), and coefficient of linear extensibility (COLE). Soil moisture (M) and water table height (WT), as well as plant biodiversity and soil type were included in the spatial variability analysis. The variables associated with water dynamics (M and WT) and soil (BD, SOC, Alp, CEC and COLE) are highly spatially dependent, with the summits, footslopes and center of the Vega all having their own unique characteristics that distinguish them from one another. Soil type and plant biodiversity also differentiate the southern and northern orientation of the Vega. Each variable is associated with an ecosystem function, such as water provision and carbon storage or productive functions, such as intensive grazing or crop establishment. There is a spatial relationship among the evaluated variables in this watershed. This was confirmed by the comparison of the results of the relevance and geostatistical analyses. The studied Vega is a highly heterogeneous ecosystem, where 3 to 5 different sectors can be identified according to the topography and the indicator used to evaluate them (e.g. summit, footslope and center or northern summit, northern high footslope, northern low footslope, center of the Vega, southern low footslope, southern high footslope and southern summit). The latter aids in defining the most appropriate potential management practice for each area, which can vary from the storage of water or carbon and more intensive grazing in the center of the Vega to the protection of biodiversity in the more xeric sectors. Xeric and mesic sectors could be used for grazing, but with caution due to the thinness of the soils. Nonetheless, it may be necessary to designate some xeric sectors with thin soils (northern summit) to biodiversity conservation alone, avoiding agricultural management altogether due to their intrinsic fragility. In contrast, the southern summit, with its deeper soils, could allow for the direct planting of species of higher forage value.