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Soil surface roughness affects surface depression storage, water infiltration, overland flow velocity as well as overland flow organisation. This paper attempts to give an overview of our knowledge of the effects of roughness on surface runoff and to indicate areas where further research is most needed. The relationship between soil surface roughness and depression storage is relatively well understood. On the other hand, few studies exist on the relationship between roughness and the infiltration characteristics of a tilled surface, although this may be more important. Insights, which have been developed over the past few years, may in the near future lead to a better prediction of the hydraulic resistance of interrill and concentrated overland flow. Recent studies have also provided important information on the effects of roughness on runoff patterns. soil roughness / depression storage / infiltration / hydraulic resistance / runoff pattern Résumé-Rugosité du sol et écoulement sur le terrain. La rugosité de la surface du sol affecte le stockage de l'eau dans les dépressions de la surface, son infiltration et la vitesse ainsi que l'organisation de l'écoulement sur le terrain. Cet article tente de donner une vue d'ensemble de nos connaissances actuelles sur les effets de la rugosité sur le ruissellement de surface et indique les domaines dans lesquels de nouvelles recherches sont les plus nécessaires. La relation entre la rugosité de la surface et le stockage de l'eau dans les dépressions est relativement bien connue. En revanche, il existe peu d'études sur la relation entre la rugosité d'une surface labourée et ses caractéristiques d'infiltration, bien que ce phénomène soit plus important. Les tentatives d'approche développées au cours des dernières années devraient conduire, dans un proche avenir, à une meilleure prédiction de la résistance hydraulique des zones de ruissellement diffus et concentré. Des études récentes ont fourni également des informations importantes sur les effets de la rugosité sur l'organisation spatiale de ruissellement. Rugosité du sol / stockage dans les dépressions / infiltration / résistance hydraulique / organisation spatiale de ruissellement

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Soil surface roughness greatly affects surface sealing and runoff generation, yet little information is available about the effect of roughness on the spatial distribution of runoff and on flow concentration. This study tested the hypothesis that runoff distribution and flow concentration differ with roughness and affect the amount of soil loss. Sequences of four rainstorms of constant rainfall amount but decreasing intensity (60, 45, 30, and 15 mm h−1) were applied to the Ap horizon material of a loess soil (Glossic Fragiudalf) packed into a 0.6 by 3.7 m flume. Rough, medium, and smooth soil surfaces were studied at 17, 8, and 2% slope steepness. Surface roughness and flow pathways were visualized with digital elevation maps obtained from laser microrelief measurements. On the smooth surfaces, runoff was uniformly distributed during the first two rainstorms and soil losses were 0.23, 0.07, and 0.12 kg m−2 for the first and 2.26, 0.35, and 0.2 kg m−2 for the second storm at 17, 8, and 2% slope steepness, respectively. On the rough and medium surfaces, flow concentrated in pathways between clods and soil losses were up to eight and three times that on the smooth surfaces during the first and second storms, respectively. During the last two storms, flow concentrated also on the smooth surfaces and soil losses were similar for the three initially different surface configurations. Surface roughness effects on runoff amount were minor, but roughness affected the spatial distribution of runoff, thereby affecting the amount of soil loss.

-The development and survival or disappearance of civilizations has been based on the performance of soils to provide food, fibre, and further essential goods for humans. Amongst soil functions, the capacity to produce plant biomass (productivity function) remains essential. This function is closely associated with the main global issues of the 21st century like food security, demands of energy and water, carbon balance and climate change. A standardised methodology for assessing the productivity function of the global soil resource consistently over different spatial scales will be demanded by a growing international community of land users and stakeholders for achieving high soil productivity in the context of sustainable multifunctional use of soils. We analysed available methods for assessing the soil productivity function. The aim was to find potentials, deficiencies and gaps in knowledge of current approaches towards a global reference framework. Our main findings were (i) that the soil moisture and thermal regime, which are climate-influenced, are the main constraints to the soil productivity potential on a global scale, and (ii) that most taxonomic soil classification systems including the World Reference Basis for Soil Resources provide little information on soil functionality in particular the productivity function. We found (iii) a multitude of approaches developed at the national and local scale in the last century for assessing mainly specific aspects of potential soil and land productivity. Their soil data inputs differ, evaluation ratings are not transferable and thus not applicable in international and global studies. At an international level or global scale, methods like agro-ecological zoning or ecosystem and crop modelling provide assessments of land productivity but contain little soil information. Those methods are not intended for field scale application to detect main soil constraints and thereby to derive soil management and conservation recommendations in situ. We found also, that (iv)

Abstract. The central importance of soil for the functioning of terrestrial systems is increasingly recognized.

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