Conversion of native grasslands into croplands in the Pampa biome and its effects on source contributions to suspended sediment of the Ibirapuitã River, Brazil
2024
Ramon, Rafael | Evrard, Olivier | Huon, Sylvain | Feitosa, Carlos Eduardo Linhares | Bernardi, Felipe | Batista, Antônio Augusto Medeiros | Tiecher, Tadeu Luis | Minella, Jean Paolo Gomes | Barros, Cláudia Alessandra Peixoto | Tiecher, Tales | Universidade Federal do Rio Grande do Sul [Porto Alegre – Brasil] = Federal University of Rio Grande do Sul [Porto Alegre – Brazil] (UFRGS) | Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE) ; Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)) ; Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA) | Géochimie Des Impacts (GEDI) ; Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE) ; Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)) ; Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)) ; Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA) | CELESTE Lab (CELESTE Lab CNRS) ; Institut national des sciences de l'Univers (INSU - CNRS) | Institut d'écologie et des sciences de l'environnement de Paris (iEES Paris) ; Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE) | Universidade Federal de Santa Maria = Federal University of Santa Maria [Santa Maria, RS, Brazil] (UFSM) | Instituto Federal Farroupilha | Instituto Federal do Rio Grande do Sul (IFRS) | CAPES-COFECUB | CNPq
International audience
Afficher plus [+] Moins [-]anglais. Grain crops have expanded at the expense of native grasslands in South America's Pampa biome in recent decades, thereby, increasing the sediment delivery to the river systems. This study aimed to evaluate the impact of land use change on sediment source contributions in the Ibirapuitã catchment (5942 km 2 ), Southern Brazil. For this purpose, a sediment fingerprinting approach was developed based on organic matter composition, ultraviolet–visible reflectance, and fallout radionuclide activities as potential tracers. Four main sediment sources were investigated: croplands ( n = 36), native grasslands ( n = 31), unpaved roads ( n = 31), and subsurface sources ( n = 34). Tracers were selected following a three‐step procedure: conservative range test, Kruskal–Wallis H‐test, and linear discriminant function analysis (LDA). Selected tracers were introduced into a mass balance mixing model to estimate the source contributions to in‐stream sediment. The seven tracers selected by the LDA were able to explain 91% of the variance and correctly classify 83% of the source samples. Despite covering less than 10% of the catchment surface area, croplands that replaced the native grasslands supplied the primary sediment source (33%) to the main outlet, followed by subsurface sources (27%). In contrast, native grasslands covering 80% of the surface area provided only 17% of sediment to the river network. These findings confirm that soil erosion processes are accelerating in response to the recent land use changes in the region. To prevent soil loss and sediment delivery to the river systems, land use conversion from native grasslands into croplands should be associated with the implementation of appropriate land conservation practices, such as runoff control, no‐tillage system, and crop rotation.
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