Fig. 2

Relationships of acid phosphatase (AP; a), β-glucosidase (BG; b), β-xylosidase (BX; c), and β-glucosaminidase (NAG; d) activities to soil carbon concentration (TC). Dashed line in each panel indicates simple linear or quadratic regression between the enzyme activity and TC. Quadratic regression is applied if simple linear regression is not significant at P < 0.05