Relationships between land cover, land use change and erosion-sedimentation processes at the watershed level: A multitemporal study in the Cointzio watershed, Mexico
Résumé
Changes in land cover and land use (LCLU) have a relevant role in current local and global change processes which are directly linked with water and soil quality, runoff and sedimentation rates. Soil erosion and sedimentation have been extensively studied at the experimental watershed or plot level, whereas in larger areas further research is needed for evaluating similar relationships. This paper aims to investigate LCLU change processes within the Cointzio watershed (Central Mexico) and its relationship to soil erosion and sediment transport processes. The analysis covers a 28-year time period from 1975 to 2003. LCLU changes were derived from a multitemporal remote sensing analysis (1975, 1986, 1996, 2000 and 2003) while long-term soil erosion was reconstructed based on lake sediment deposition data. We found that 46 % all of the LCLU changes occurred between 1986 and 1996. Sedimentation discharge remained stable over the 1975-2003 period (1.4±0.6 g.cm-2.y-1), with the exception of two peaks (1975-1977 and 1991-1994; 3.1±0.6 and 2.6±0.6 g.cm-2.y-1, respectively) caused by exceptional rainfall events. The processes did not lead to changes in soil erosion and sediment transport rate likely due to the simultaneous positive (forest transition and scrubland increase) and negative changes (deforestation and forest degradation). We concluded that the poor correlation of LCLU changes to sediment discharge can be explained by a balance between negative changes that promote land degradation processes (e.g., erosion, mass wasting) and positive ones that reduce these kind of processes.