In the present work, land cover and land use changes between 2003 and 2008 were assessed in the Cupatitzio River sub‐basin located in the Trans‐Mexican Volcanic System and Balsas Depression in Mexico. The effects of land cover conversion from temperate forest to avocado orchards on soil properties were determined. Land cover and land use databases were built for the years 1975, 2003, and 2008 using available cartographic information and interpretation of panchromatic SPOT images for the year 2008. Additionally, soil sampling was carried out in 16 representative sites in the higher parts of the sub‐basin, where avocado plantation dynamics have caused important changes in areas covered by temperate forests. Results show that (i) temperate coniferous and tropical low deciduous forests were reduced at an annual rate of 0·9 per cent (1, 001 ha y−1) between 1975 and 2008; (ii) cropland areas expanded at an annual rate of 0·7 per cent between 1975 and 2008, representing a growth of 553 ha y−1; (iii) wet soil aggregate stability, mechanical resistance to penetration and nitrate (N‐NO3) concentration in the topsoil layer of Andosols were significantly affected by land use conversion to avocado orchards. Other soil properties such as organic matter, interchangeable K, and available P showed degradation tendencies. These results suggest the importance of implementing strategies for mitigating the accelerated process of transformation and degradation of natural resources in the Cupatitzio River sub‐basin. The implementation of programs for deforestation reduction should be a priority in the restoration strategy. Copyright © 2012 John Wiley & Sons, Ltd.

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In the Transmexican Volcanic Belt a traditional fallow system is practiced, called “año y vez” (AV), which does not benefit soil conservation due to its low level of nutrient recycling and because soil protection is poor during the cultivation year. The objective of the present work was to measure runoff and soil and nutrient losses during three annual cycles (2002–2004) in Central Mexico under AV rotation and two alternative systems: improved traditional (IT) and traditional organic (TO). Soil losses in the three systems were moderate (<1.2 Mg ha−1 y−1) except during 2002, in which significant soil losses were recorded in IT and TO due to the scarcity of plant cover (<20 per cent) that was present throughout the rainy season. During the resting period of the AV system (2003), the annual runoff increased from 19 to about 600 per cent, compared to IT and TO without grazing. The difference in runoff was attributed to an 18 per cent increase in bulk density of soil surface (0–5 cm) caused by cattle trampling while grazing. Nutrient losses in the three treatments were mainly of N, Ca2+, Mg2+, Na+, and K+. These results suggest that AV has a higher topsoil degradation effect during the resting year than during the cultivation period. The study shows that incorporating the maize/beans‐black oat rotation and residue cover causes a low runoff response that is important in reducing soil degradation. A spatial analysis is presented of erosion at watershed level for two soil management systems assessed. Copyright © 2009 John Wiley & Sons, Ltd.

Effective management options for mitigating the loss of reservoir water storage capacity to sedimentation depend on improved predictions of bed-load discharges into the reservoirs. Most predictions of bed-load discharges, however, are based on the assumption that the rates of bed-load sediment availability equal the transport capacity of the flow, ignoring the spatio-temporal variability of the sediment supply. This paper develops a semiquantitative method to characterize bed-load sediment transport in alluvial channels, assuming a channel reach is non-supply limited when the bed-load discharge of a given sediment particle-size class is functionally related to the energy that is available to transport that fraction of the total bed-load. The method was applied to 22 alluvial stream channels in the USA to determine whether a channel reach had a supply-limited or non-supply-limited bed-load transport regime. The non-supply-limited transport regime was further subdivided into two groups on the basis of statistical tests. The results indicated the pattern of bed-load sediment transport in alluvial channels depends on the complete spectrum of sediment particle sizes available for transport rather than individual particle-size fractions represented by one characteristic particle size. The application of the method developed in this paper should assist reser voir managers in selecting bed-load sediment transport equations to improve predictions of bed-load discharge in alluvial streams, thereby significantly increasing the efficiency of management options for maintaining the storage capacity of waterbodies.