1 A survey of plant and soil parameters was carried out in dry dune grasslands along the Dutch coast in the lime‐ and iron‐poor Wadden district and initially lime‐ and iron‐rich Renodunaal district, in order to detect differences in nutrient availability related to soil characteristics and potential sensitivity to atmospheric deposition of nitrogen. 2 Plant biomass and phosphorus pools in the shoot were higher in the Wadden district. The low foliar nitrogen concentrations and nitrogen/phosphorus ratios in the Wadden district suggested nitrogen‐limitation, while in the Renodunaal district there appeared to be a balanced supply of both nitrogen and phosphorus. 3 Soil pH, soil organic matter, soil nitrogen and phosphorus concentrations and total amounts were generally higher in the Renodunaal district. In both districts mineral phosphorus decreased with acidification and phosphorus oxalate (iron and aluminium bound) increased. 4 In the Wadden district iron is present primarily in iron–organic matter complexes, which leads to reversible binding of phosphorus. In the Renodunaal district large amounts of iron (hydr)oxides occur and at high pH may contribute to reversible phosphorus‐sorption, but at low pH this probably leads to immobilization of phosphorus. 5 While pools of soil phosphorus are low in the Wadden district, the phosphorus availability may be relatively high due to the comparatively loose nature of phosphorus‐sorption. As a result the area may be nitrogen‐limited and grass‐encroachment may thus have resulted from atmospheric deposition of nitrogen. 6 In the Renodunaal district, atmospheric deposition probably only accelerates grass‐encroachment, because deposition of acid and nitrogen increases the availability of both nitrogen and phosphorus and maintains the ‘co‐limitation’.

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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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