Abstract:

Aims In the traditional Chinese medicine resources survey process, quadrat size and number must be determined before surveying. Our objective is to determine how to select the optimal quadrat size and number for Dipsacus asperoides.
Methods We examined D. asperoides cultivated in Longli, Qiannan Autonomous Prefecture, Guizhou Province. We first calculated aboveground volume of D. asperoides by a segment model. Then we selected the optimal quadrat size and number by using the quadrat-based transect survey method, and calculated the optimal quadrat number by the variance method.
Important findings When only considering of the relative mean of aboveground volume and relative time costs, 25 m × 25 m is the optimal size. But when further considering quadrat boundary effects and variation in relative mean of the aboveground volume, the optimal size is 25 m × 50 m. If the expected confidence level is 0.9, the absolute margin of error is 0.12, the population variance S ² obtained conventionally is 0.25 and the optimal quadrat number is 25. This study sampled 25 quadrats of 25 m × 50 m within the entire area of the cultivated garden (72696.24 m ²). The total aboveground volume of D. asperoides with approximately 90% confidence located in the extent is [1909.798 m ³, 2214.762 m³]. Results showed that the optimal quadrat size from the nested quadrats method and the segment model are useful in estimating the aboveground volume of cultivated D. asperoides, and they can provide a reference for other surveys.

Key words: a segment model, boundary effects, nested quadrats, optimal quadrats, relative cost