At different scales, certain different processes prevail. The simplest example of this is found in sediments: small particles, such as clays, are ‘stickier’ as cohesive forces are relatively more important when the particles get smaller; see Hjulstrom diagram. In biogeography, a major scale-dependence notion is that different ecological patterns and processes are dominant at different spatial scales. This notion in turn implies that changes in scale, be it the size of unit plot or the size of study area, involve a change in the correlation structure among biotic and abiotic components; see Kim et al. (2012) AAAG 102, 2, 276. Wei et al. (2012) Chin. Geogra. Sci. 22, 2, 127 show that the driving forces and mechanisms of water erosion variations are quite different at different scales.