Crossing a critical threshold: Accelerated and widespread land use changes drive recent carbon and nitrogen dynamics in Vichuquen Lake (35°S) in central Chile

Global afforestation/deforestation processes (e.g., Amazon deforestation and Europe afforestation) create new anthropogenic controls on carbon cycling and nutrient supply that have not been fully assessed. Here, we use a watershed-lake dynamics approach to investigate how human-induced land cover changes have altered nutrient transference during the last 700 years in a mediterranean coastal area (Vichuquen Lake). We compare our multiproxy reconstruction with historical documentation and use satellite images to reconstruct land use/cover changes for the last 45 years. Historical landscape changes, including those during the indigenous settlements, Spanish conquest, and the Chilean Republic up to mid-20th century did not significantly alter sediment and nutrient fluxes to the lake. In contrast, the largest changes in the lake-watershed system occurred in the mid-20th century and particularly after the 1980s-90s and were characterized by a large increase in total nitrogen and organic carbon fluxes as well as negative shifts in sediment delta N-15 and delta C-13 values. This shift was coeval with the largest land cover transformation in the Vichuquen watershed, as native forests nearly disappeared while anthropogenic tree plantations expanded up to 60% of the surface area. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study reveals that human-induced land cover changes around Vichuquen Lake in Chile have had significant impacts on the nutrient transfer in the lake-watershed system. Particularly after the mid-20th century and in the 1980s-90s, there were substantial changes in sediment and nutrient fluxes to the lake.