Objective  The aim is to reveal the differential effects of exudate components on the activities of soil microorganisms and their extracellular enzymes.

  Method  In well-controlled rhizosphere systems, glucose, oxalic acid and glycine solutions were separately added to soils collected from a southwest subalpine spruce plantation (approximately 70 years old) via artificial roots, and incubated for 25 days (a total of 70.65 mg C was added).

  Result  Glucose addition significantly increased the activities of almost all microbial communities (except the gram-negative bacteria). Oxalic acid addition also significantly increased the activities of most of the microbial communities (e.g., gram-positive bacteria and gram-negative bacteria and total microbial communities). However, the increments of activities of the microbial communities from glucose addition was higher than that observed from oxalic acid addition. In contrast, glycine addition tended to exert an inhibiting effect on microbial activities. In addition, glucose and oxalic acid additions significantly increased the activities of β-1,4-glucosidase and peroxidase (acid phosphatase and polyphenol oxidase activities showed an increasing trend), respectively, while the addition of glycine had little effect on the activities of extracellular enzymes.

  Conclusion  The three exudate components (glucose, oxalic acid and glycine) exert different influences on soil microbial activity, community composition and extracellular enzymes. This discrepancy may be due to the differences in chemical functional groups and energy properties of the exudate components. Therefore, the component-specialized microbial and enzymatic properties induced by individual exudate components on rhizosphere processes under future study of biogeochemical cycling should be taken into account.