Factors affecting forest formation in abandoned terraced paddy fields in a mountainous region
2008
Sato, T.(Niigata Univ. (Japan)) | Nakata, M.
Factors affecting forest formation were studied in abandoned terraced paddy fields in a mountainous region of Sado Island, Niigata Prefecture, Japan. Shortly before or after the study area was abandoned about 40 years ago, the migration of Quercus serrata, Castanea crenata, and other tree species started in the terraced paddy fields and progressed gradually until about 20 years ago. Forest formation in the abandoned fields was affected strongly by groundwater levels due to the slope position and the soil water environment caused by differences in microtopography, namely, paddy plane, levee, and levee slope. At higher positions on the slope, where the groundwater level was low and hence the soil water content was not excessively high, trees had grown in every part of the paddy field. However, at lower positions on the slope, where the groundwater level was high and hence the soil water content at the paddy plane was high, the forest canopy was closed by trees growing mainly on the levees or levee slopes where there was lower excess soil water. Soil water content and tree growth were affected by the inclination of the levee slopes. The different distribution patterns of tree species by microtopography of the terraced paddy fields might be related to the seed dispersal types and physiological tolerance of individual species to the soil water environment.
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