Timing for the collection of topsoil from a deciduous forest for use as planting material in suburban Tokyo, Japan

Abstract

In Japan, government and ecological scientists recommend that indigenous species should be used in planting to maintain biodiversity. Using forest topsoil is an efficient planting strategy for indigenous species. We wanted to find the best time of year for collecting forest topsoil. We regularly collected topsoil throughout 1 year from a deciduous forest in suburban Tokyo. The soil seed bank composition was estimated by recording seedling emergences. Additionally, the seed rain, influence of predation to dispersed seeds, and seedling emergence at the forest floor were also estimated. The soil seed bank composition did not change greatly during the year studied; however, the buried seeds were abundant comparatively in January and April. Therefore, it was suggested whenever possible to collect forest topsoil as planting material. Additionally, we suggested that the best time to collect topsoil was from November to February. This was also supported by the results of seed rain and seedling emergences at the forest floor added to the result of the seed bank. A method of measuring the value of soil seed bank as a planting material was evaluated. An evaluation based on seed density of pioneer tree species was suitable for even small amounts of topsoil.