Laubstreu

Laubstreu, or leaf litter, is the layer of fallen leaves and other plant debris that covers the forest floor. It forms part of the soil’s organic matter and varies with tree species, climate, and season. In deciduous forests, leaves dominate the litter; in coniferous forests, needles and cone scales are common components. The thickness of the layer can range from a thin film to several centimeters, influenced by productivity, disturbance, and decomposition rate.

The litter accumulates as leaves fall, but it also decomposes before and after reaching the ground. Decomposition is driven by fungi, bacteria, and detritivores such as mites, springtails, beetles, and earthworms. Temperature, moisture, litter quality (including lignin and tannin content), and soil biology regulate the pace of breakdown. As litter decomposes, nutrients are mineralized and recycled into the soil, supporting plant growth and microbial activity.

Ecologically, laubstreu provides moisture retention and soil insulation, reduces erosion, and creates microhabitats for a diversity of organisms. It influences seed germination and establishment by altering light, temperature, and soil moisture at the surface. The litter layer also contributes to carbon storage in forest soils, though much of the carbon ultimately becomes part of the humus as decomposition proceeds.

Management and uses vary. In forestry and conservation, leaving the litter on the forest floor protects soil structure and biodiversity, while removal can reduce nutrient inputs and increase erosion. In horticulture, leaf litter is often used as mulch or composted. In German soil terminology, laubstreu refers specifically to the fresh-to-decomposed plant debris on the surface, distinct from humus (fully decomposed organic matter) and duff (partially decomposed material embedded in the soil.