Topography and Land Use Modulate Hydrological and Nutrient Export Dynamics in Andean Streams

Waterways act as integrators of ecosystems, their dynamics driven by multiple environmental factors and scales. To elucidate factors affecting hydrological and nutrient dynamics in Andean streams, we characterized two adjacent North Patagonian streams with contrasting drainage basins: Casa de Piedra (CP), originating in a small mountain lake and running through a pristine landscape, and Gutiérrez (G), originating in a large piedmont lake and running through an anthropized landscape. The drainage basins share both temperature and precipitation regimes; however, the streams presented contrasting hydrological dynamics and nutrient export values. CP had higher discharge flashiness with shorter response delays to precipitation, while G showed more stable hydrograms, a difference explained by buffering from a large upstream lake in G’s basin. Streams showed differences in the quality and timing of coarse particulate organic matter export and basal export levels of phosphorus and nitrogen that could be explained by human activities affecting G but not CP. Moreover, nitrogen:phosphorus ratio indicates a possible shift to phosphorus as the limiting nutrient in the future in G drainage basin. In summary, our results show that even under a common climatic regime, dynamics of adjacent basins can be strongly driven by topographic and land use factors.