and dead plant residues of any size. A litter layer is a loose layer that contains > 90% (by volume, related to the fine earth plus all dead plant residues) recognizable dead plant tissues (e.g. undecomposed leaves). Dead plant material still connected to living plants (e.g. dead parts of Sphagnum mosses) is not regarded to form part of a litter layer. The soil surface (0 cm) is by convention the surface of the soil after removing, if present, the litter layer and, if present, below a layer of living plants (e.g. living mosses). The mineral soil surface is the upper limit of the uppermost layer consisting of mineral material. A soil layer is a zone in the soil, approximately parallel to the soil surface, with properties different from layers above and/or below it. If at least one of these properties is the result of soil-forming processes, the layer is called a soil horizon. In the following, the term layer is used to indicate the possibility that soil-forming processes did not occur. The following layers are distinguished (see Chapter 3.3 of the WRB Manual): Organic layers consist of organic material: Have ≥ 20% organic carbon, not consisting of artefacts (related to the fine earth plus the dead plant residues of any length and a diameter ≤ 5 mm) and do not form part of a litter layer. Organotechnic layers consist of organotechnic material: Have ≥ 35% (by volume, related to the whole soil) artefacts containing ≥ 20% organic carbon; and < 20% organic carbon, not consisting of artefacts (related to the fine earth plus the dead plant residues of any length and a diameter ≤ 5 mm). Mineral layers are all other layers. The designation consists of a capital letter (master symbol), which in most cases is followed by one or more lowercase letters (suffixes). Master symbols H: Organic or organotechnic layer, not forming part of a litter layer; water saturation > 30 consecutive days in most years or drained; generally regarded as peat layer or organic limnic layer. O: Organic horizon or organotechnic layer, not forming part of a litter layer; water saturation ≤ 30 consecutive days in most years and not drained; generally regarded as non-peat and non-limnic horizon. A: Mineral horizon at the mineral soil surface or buried; contains organic matter that has at least partly been modified in-situ; soil structure and/or structural elements created by cultivation in