Table 1

Variables extracted from the native habitats of Rheum tanguticum Maxim. ex Balf based on TCMGIS-II combined geographic, climate and soil type databases

Variable

Unit

Range

Mean ± SE

F-value

C_v(%)

Elevation

m

1980, 4550

3630 ± 44

191.2***

17.4

Relative humidity

%

54.8, 69.0

63.7 ± 2.2

219.3***

49.6

Sunshine duration

hr/yr

1897, 2704

2450 ± 13

301.7***

7.6

Annual precipitation

mm

331, 839

574 ± 7

233.2***

17.5

Accumulated temperature

°C

3193, 22451

9517 ± 951

277.1***

143.4

Mean annual temperature

°C

5.1, 13.1

8.6 ± 0.1

92.6***

16.7

Mean March temperature

°C

-8.0, -2.0

-4.5 ± 0.2

42.3***

63.8

Minimum temperature

°C

-24.8, -10.6

-19.1 ± 0.2

165.8***

15.0

Maximum temperature

°C

12.9, 24.4

17.2 ± 0.2

119.5***

16.7

Mean minimum temperature

°C

-15.6, -5.1

-11.2 ± 0.2

129.8***

25.6

Mean maximum temperature

°C

6.0, 18.2

10.4 ± 0.2

103.3***

27.6

Soil type*

pH

5.9, 8.5

6.8 ± 0.1

112.4***

21.1

* Soil type was assigned according to soil grade division in TCMGIS-II program.

Values of pH were employed as an indicator of soil types for statistical analysis.

F-value indicates the difference in target variable extracted from different native habitats (*** P < 0.001, ** P < 0.01, and * P < 0.05).

SE: standard error of means

C_v: coefficient of variation

Yu et al. Chinese Medicine 2010 5:31   doi:10.1186/1749-8546-5-31