Timing for the planting method using deciduous forest topsoil in suburban Tokyo, Japan

The suitable time for planting using the topsoil of a warm temperate deciduous forest is discussed based on the germination characteristics of the soil seed bank. Forest topsoil was collected regularly over a 1-year period from a deciduous forest in suburban Tokyo, and seedling emergence in the outdoors was recorded immediately after collection. Many seedlings were observed from February to May, indicating that this is the best time for planting because this is when most buried seeds germinate. Additionally, it was inferred that buried seeds germinate immediately after planting during the period from February to October, although the quantity of seed germination varies according to the season. The method of evaluating the forest topsoil as a planting material is also discussed. The simple and preferred method of evaluation is to examine outdoor seedling emergence from February to May. Accurate evaluation during the summer and autumn months proved problematic, especially when counting tree seeds, and it was necessary to continue the evaluation into the following spring. A practical understanding of the timing of planting and the method of evaluating forest topsoil as a planting material is possible in warm temperate areas.