Abstract:Spatial variability in contents of active constituents, scutellarin and caffeates, from 310 samples in 94 natural populations of Erigeron breviscapus, a medicine herb, was analyzed in nested ANOVA within the producing areas of this medicine herb, based on the sampling regime designed following the nested design principle. Results indicated that there were variations in caffeates and scutellarin content of E. breviscapus growing in different producing areas, average contents of caffeates and scutellarin in the lowest content producing areas were 52.1% and 41.8% of that in the highest content producing area respectively. The difference of contents was not related to the spatial distance between producing areas. The content of caffeates or scutellarin varied annually in the same producing area, but the location of the highest or lowest content producing area did not change. The natural division was better to delimit the units of high content producing area than administrativ division. The content of caffeates or scutellarin was negatively correlated with the content of nitrogen in plants growing in different areas, as predicted as carbon/nutrient balance hypothesis. The variation in nitrogen content explained about 30% of the variation in the content of caffeates or scutellarin of plant from different areas. The spatial variability in active constituent content of medicine herbs was resulted from their genetic and environmental variation. Delimiting the producing area of medicine herbs is a scientific management way to keep efficiency of medicine herb.