Effects of plant root exudates enzyme activities on rhizosphere soil enzyme activities and nutrients in karst areas

Abstract

In order to explore the effects of enzyme activities from plant root exudates on rhizosphere soil enzyme activities and nutrients in karst areas, the activities of β-1,4-glucosidase (βG), β-N-acetyl-glucosaminidase (NAG), leucine aminopeptidase (LAP), and acidic phosphatase (ACP) of fine root exudates and rhizosphere soils in four vegetation restoration stages, which are shrub-grassland, shrubland, shrub-arbor forest and arbor forest, were measured. And, their relationships with soil carbon (C), nitrogen (N), phosphorus (P) contents were analyzed. The results were as follows: (1) The four enzyme activities of rhizosphere soils and root exudates were significantly higher in the late stage of vegetation restoration than that in the early stage of vegetation restoration. The enzyme activities C∶P to N∶P ratios of root exudates in arbor forest were significantly higher than those of other three stages, while the two parameters of rhizosphere soils were opposite. (2) Correlation analysis showed that the enzyme activities of root exudates were positively correlated with the corresponding soil enzyme activity. Compared with the enzyme activities of root exudates, the correlation between soil enzyme activity and related nutrients became significantly stronger. In addition, the enzyme activities of βG, NAG and LAP in rhizosphere soils and root exudates were positively correlated with soil organic carbon (SOC) and total nitrogen (TN) in rhizosphere soil, while the enzyme activities of ACP in rhizosphere soils and root exudates were positively correlated with available phosphorus (AP) in rhizosphere soil. The above results indicate that vegetation restoration has positive effects on increasing enzyme activities of root exudates and soils. The enzymes of root exudates are the indispensable supplements for soils, and play an important role in promoting carbon, nitrogen and phosphorus nutrient cycling. To sum up, it will be that the regulation of root exudates and its enzyme activities may provide a new perspective for vegetation restoration in karst ecosystem.

Keywords

• karst ecosystem
• vegetation restoration
• root exudates enzyme activity
• soil enzyme activity
• soil nutrients