title: Determination of production regions for pollution-free Chinese medicinal materials by geographic information system: Achyranthes bidentata (Niu Qi) in Tianjin as an example.
abstract: BACKGROUND
  The land and ecology suitability for producing pollution-free Chinese medicinal materials should be evaluated based on Geographic Information System (GIS). This study aims to determine production regions for pollution-free Achyranthes bidentata in Tianjin as a case to illustrate the workflow based on GIS.
  
  
  METHODS
  The slopes, land usage, residential areas and roads were selected to evaluate the land suitability, to avoid the potential pollution sources. The ecology suitability evaluation was performed based on the soil type and nine climate factors, such as active accumulated temperature, mean January temperature, mean July temperature, the lowest temperature in January, the highest temperature in July, mean annual temperature, sunshine duration, relative humidity, annual precipitation, affecting the natural growth of A. bidentata.
  
  
  RESULTS
  The best production regions for pollution-free A. bidentata in Tianjin, with a total area of approximately 575 km(2), were found in Jinghai County, Ninghe County, Wuqing District, and Dagang District.
  
  
  CONCLUSIONS
  This study illustrated a workflow based on GIS for determining the production regions in Tianjin for pollution-free A. bidentata.
authors.affiliation: The Key Laboratory of Bioactive Substances and Resources Utilization of Chinese Herbal Medicine, Ministry of Education, Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100193, P. R. China.
authors.forename: Cai-Xiang
authors.initials: CX
authors.lastname: Xie
authors.affiliation: The Key Laboratory of Bioactive Substances and Resources Utilization of Chinese Herbal Medicine, Ministry of Education, Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100193, P. R. China.
authors.forename: Huan
authors.initials: H
authors.lastname: Wang
authors.affiliation: The Key Laboratory of Bioactive Substances and Resources Utilization of Chinese Herbal Medicine, Ministry of Education, Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100193, P. R. China.
authors.forename: Lin-Fang
authors.initials: LF
authors.lastname: Huang
authors.affiliation: The Key Laboratory of Bioactive Substances and Resources Utilization of Chinese Herbal Medicine, Ministry of Education, Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100193, P. R. China.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.affiliation: The Key Laboratory of Bioactive Substances and Resources Utilization of Chinese Herbal Medicine, Ministry of Education, Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100193, P. R. China.
authors.forename: Jing-Yuan
authors.initials: JY
authors.lastname: Song