CONICET | Buscador de Institutos y Recursos Humanos

Soil total nitrogen (N) stock in rangelands, shrublands, and forests support key ecologicalfunctions such as the capacity of the land to sustain plant and animal productivity and ecosystemservices. The objective of this study was to model soil total N stocks and soil C/N ratio from 0?30 cmdepth across the region using freely accessible information on topography, climate, and vegetationwith a view to establishing a baseline against which sustainable land management practices canbe evaluated in Southern Patagonia. We used stepwise multiple regression to determine whichindependent variables best explained soil totalNvariation across the landscape in Southern Patagonia.We then used multiple regression models to upscale and produce maps of soil total N and C/N acrossthe Santa Cruz province. Soil total N stock to 30 cm ranged from 0.13 to 2.21 kg N m􀀀2, and soilC/N ratios ranged from 4.5 to 26.8. The model for variation of soil total N stock explained 88% ofthe variance on the data and the most powerful predictor variables were: isothermality, elevation,and vegetation cover (normalized dierence vegetation index (NDVI)). Soil total N and soil C/Nratios were allocated to three categories (low, medium, high) and these three levels were used to mapthe variation of soil total N and soil C/N ratios across Southern Patagonia. The results demonstratethat soil total N decreases as desertification increases, probably due to erosional processes, and thatsoil C/N is lower at low temperatures and increased with increasing precipitation. Soil total N andsoil C/N ratios are critical variables that determine system capacity for productivity, especially theprovisioning ecosystem services, and can serve as baselines against which eorts to adopt moresustainable land management practices in Patagonia can be assessed.

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