Dynamics of secondary forest and its perspective under the Satoyama system in Saitama prefecture, Japan

The Satoyama landscape is a mosaic system of land use in Japan, comprising secondary forests, croplands and settlements. The various ecosystem services provided by the interactions between humans and the environment at the landscape level are together known as the “Satoyama system”. Land use and structural changes in secondary forest were quantitatively evaluated based on analysis of land and forest distribution and dynamics in 1961, 1975 and 2016 within the Satoyama landscape of Saitama prefecture, central Japan. Most secondary forests were replaced by settlements, which was driven by typical socio-economic factors (i.e. a rise in land value) and land use change largely relating to the decline in the agricultural demand for compost made from forest litterfall. The dynamics and structural changes of land and forest revealed that land use in the Satoyama landscape had become more uniform as a result of changing human activities and land use. Organic carbon and nitrogen contents were smaller in secondary forest that was still being managed by the collection of litterfall than abandoned secondary forest with no litterfall collection, especially to a depth of 0.25 to 0.30 m. This has resulted in a decline in CO₂ sequestration in managed secondary forest although abandoned secondary forest and/or plant-derived organic matter inputted cropland keep or increase CO₂ sequestration. Considering a mosaic system of land use comprising secondary forests, croplands and settlements, an adaptive management procedure suited for present-day needs, is therefore required to maintain sustainable use of the Satoyama landscape in the future.