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In arable farming systems, the term ‘subsoil’ refers to the soil beneath the tilled or formerly tilled soil horizon whereas the latter one is denoted as ‘topsoil’. To date, most agronomic and plant nutrition studies have widely neglected subsoil processes involved in nutrient acquisition by crop roots. Based on our current knowledge it can be assumed that subsoil properties such as comparatively high bulk density, low air permeability, and poverty of organic matter, nutrients and microbial biomass are obviously adverse for nutrient acquisition, and sometimes subsoils provide as little as less than 10% of annual nutrient uptake in fertilised arable fields. Nevertheless, there is also strong evidence indicating that subsoil can contribute to more than two-thirds of the plant nutrition of N, P and K, especially when the topsoil is dry or nutrient-depleted. Based on the existing literature, nutrient acquisition from arable subsoils may be conceptualised into three major process components: (I) mobilisation from the subsoil, (II) translocation to the shoot and long-term accumulation in the Ap horizon and (III) re-allocation to the subsoil. The quantitative estimation of nutrient acquisition from the subsoil requires the linking of field experiments with mathematical modelling approaches on different spatial scales including Process Based Models for the field scale and FunctionaleStructural Plant Models for the plant scale. Possibilities to modify subsoil properties by means of agronomic management are limited, but ‘subsoiling’ e i.e. deep mechanical loosening e as well as the promotion of biopore formation are two potential strategies for increasing access to subsoil resources for crop roots in arable soils. The quantitative role of biopores in the nutrient acquisition from the subsoil is still unclear, and more research is needed to determine the bioaccessibility of nutrients in subsoil horizons.

The soils in the highlands of north-eastern Rio Grande do Sul (Brazil) are distributed in a mosaic of grassland and deciduous forest with the conifer Araucaria angustifolia. The objectives of this study were (1) to identify the relationships between vegetation mosaic and soil properties, (2) to reconstruct the vegetation history, (3) to investigate if the composition of soil organic matter is associated with vegetation changes. Overall, the results of this investigation are important contributions for a better understanding of vegetation history in the southern Brazilian highlands. This was achieved by characterising soil organic matter, especially by the combined evaluation of the chemical composition and the carbon isotope signatures. In addition, this study revealed that the formation and permanence of nonallophanic Andosols is related to grass vegetation, whereas Araucaria forest establishment results in the development of Umbrisols and the loss of andic properties., Im subtropischen Hochland von Rio Grande do Sul (Brasilien) besteht ein mosaikartiger Wechsel von Grasland und Laubwald mit der Konifere Araucaria angustifolia. Diese Arbeit hatte als Ziel, (1) die Beziehungen zwischen Vegetationsmuster und Bodeneigenschaften zu identifizieren, (2) die Vegetationsgeschichte zu rekonstruieren, (3) den Einfluss von Vegetationswechsel auf die chemische Zusammensetzung der organischen Bodensubstanz zu untersuchen und (4) die Herkunft von Lignin in Böden und dessen Bedeutung für den Verlauf der 13C/12C Isotopensignatur festzustellen. Diese Arbeit leistet einen wichtigen Beitrag für das Erfassen der Vegetationsgeschichte im südbrasilianischen Hochland. Die Grundlage hierfür war die Charakterisierung der organischen Bodensubstanz, insbesondere die Bewertung der chemischen Zusammensetzung in Kombination mit der Signatur der stabilen Kohlenstoffisotope. Diese Untersuchung zeigt, dass die Bildung und Erhaltung von Andosolen an Grasvegetation geknüpft ist.

The soils in the highlands of north-eastern Rio Grande do Sul (Brazil) are distributed in a mosaic of grassland and deciduous forest with the conifer Araucaria angustifolia. The objectives of this study were (1) to identify the relationships between vegetation mosaic and soil properties, (2) to reconstruct the vegetation history, (3) to investigate if the composition of soil organic matter is associated with vegetation changes. Overall, the results of this investigation are important contributions for a better understanding of vegetation history in the southern Brazilian highlands. This was achieved by characterising soil organic matter, especially by the combined evaluation of the chemical composition and the carbon isotope signatures. In addition, this study revealed that the formation and permanence of nonallophanic Andosols is related to grass vegetation, whereas Araucaria forest establishment results in the development of Umbrisols and the loss of andic properties., Im subtropischen Hochland von Rio Grande do Sul (Brasilien) besteht ein mosaikartiger Wechsel von Grasland und Laubwald mit der Konifere Araucaria angustifolia. Diese Arbeit hatte als Ziel, (1) die Beziehungen zwischen Vegetationsmuster und Bodeneigenschaften zu identifizieren, (2) die Vegetationsgeschichte zu rekonstruieren, (3) den Einfluss von Vegetationswechsel auf die chemische Zusammensetzung der organischen Bodensubstanz zu untersuchen und (4) die Herkunft von Lignin in Böden und dessen Bedeutung für den Verlauf der 13C/12C Isotopensignatur festzustellen. Diese Arbeit leistet einen wichtigen Beitrag für das Erfassen der Vegetationsgeschichte im südbrasilianischen Hochland. Die Grundlage hierfür war die Charakterisierung der organischen Bodensubstanz, insbesondere die Bewertung der chemischen Zusammensetzung in Kombination mit der Signatur der stabilen Kohlenstoffisotope. Diese Untersuchung zeigt, dass die Bildung und Erhaltung von Andosolen an Grasvegetation geknüpft ist.