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	サイトインデックス曲線	林分密度指数
分野	林学	林学
系統	Process / pipeline	Process / pipeline
提唱年	1954	1933
提唱者	Joseph Westveld	Louis Reineke
種類	productivity index	density measurement
原典	Clutter, J. L., Fortson, J. C., Pienaar, L. V., Brister, G. H., & Bailey, R. L. (1983). Timber Management: A Quantitative Approach. John Wiley & Sons.	Reineke, L. H. (1933). Perfecting a stand-density index for even-aged forests. Journal of Agricultural Research, 46(7), 627–638.
別名	site productivity, growth intercept	SDI, Reineke density index
関連	1	2
概要	A site index curve is a family of curves relating tree height to stand age, used to quantify the productivity of a forest site. Site index is conventionally defined as the height of dominant trees at a reference age (typically 50 years in temperate forests). These curves enable foresters to classify sites by productivity class and to predict growth rates for planning timber harvests and silvicultural treatments. Site index curves are among the most fundamental tools in forest growth and yield modeling.	The Stand Density Index (SDI), introduced by Reineke in 1933, is a dimensionless measure of forest density that accounts for both tree number and size. It expresses the number of trees per hectare in a stand, adjusted to a reference quadratic mean diameter (QMD) of 25 cm, providing a standardized metric for comparing tree density across different forest types and sizes. SDI is widely used in forest management to assess stocking levels and to guide thinning decisions.