Response of enzyme activities and microbial communities to soil amendment with sugar alcohols

Abstract

Changes in microbial community structure are widely known to occur after soil amendment with low-molecular-weight organic compounds; however, there is little information on concurrent changes in soil microbial functional diversity and enzyme activities, especially following sorbitol and mannitol amendment. Soil microbial functional diversity and enzyme activities can be impacted by sorbitol and mannitol, which in turn can alter soil fertility and quality. The objective of this study was to investigate the effects of sorbitol and mannitol addition on microbial functional diversity and enzyme activities. The results demonstrated that sorbitol and mannitol addition altered the soil microbial community structure and improved enzyme activities. Specifically, the addition of sorbitol enhanced the community-level physiological profile (CLPP) compared with the control, whereas the CLPP was significantly inhibited by the addition of mannitol. The results of a varimax rotated component matrix demonstrated that carbohydrates, polymers, and carboxylic acids affected the soil microbial functional structure. Additionally, we found that enzyme activities were affected by both the concentration and type of inputs. In the presence of high concentrations of sorbitol, the urease, catalase, alkaline phosphatase, β-glucosidase, and N-acetyl-β-d-glucosaminidase activities were significantly increased, while invertase activity was decreased. Similarly, this increase in invertase, catalase, and alkaline phosphatase and N-acetyl-β-d-glucosaminidase activities was especially evident after mannitol addition, and urease activity was only slightly affected. In contrast, β-glucosidase activity was suppressed at the highest concentration. These results indicate that microbial community diversity and enzyme activities are significantly affected by soil amendment with sorbitol and mannitol.

Keywords: Biolog CLPP; enzyme activity; soil microbial community; sugar alcohols.

Figure 1

Variation in the average well color development of substrate utilization profiles of soil treated with (A) sorbitol and (B) mannitol. C0.25, C0.5, and C1 represent concentrations of 0.25, 0.5, and 1.0 g/kg dry weight soil after addition of sorbitol and mannitol, respectively. Vertical bars represent the standard error.

Figure 2

Principal component analysis of the soil microbial community‐level physiological profiles of the soils treated with sorbitol and mannitol. Triangle represents sorbitol treatment; diamond represents mannitol treatment; circle represents control.

Figure 3

Soil enzyme activities of sorbitol‐ and mannitol‐treated soils. Soil (A) invertase, (B) calatase, (C) alkaline phosphatase, (D) urease, (E) β‐glucosidase and (F) N‐acetyl‐β‐d‐glucosaminidase activities. Values are mean ± SE, and letters denote significant differences among sugar alcohol concentrations (P < 0.05).