ObjectiveSoil enzymes are involved in all soil biochemical processes and are closely related to soil physicochemical properties. In this paper, three typical woodlands in karst faulted basins were studied, and the relationships between soil enzyme activities and physicochemical properties of forest lands were explored, which provided a reference for vegetation ecological restoration in this area.

MethodIn this study, the Pinus yunnanensis, Eucalyptus maideni and natural secondary forest in the karst faulted basin were used as research objects. The relationship between soil enzyme activities and physicochemical properties was studied using the methods of redundancy analysis.

Result(1) The soil pH values of the three forest lands ranged from 5.47 to 6.03, and the soil bulk densities of the 10−20 cm and 20−30 cm soil layers in the Pinus yunnanensis forest were significantly higher than those of the Eucalyptus maideni forest and the secondary forest (P < 0.05). The contents of total nitrogen (TN) in 0−10 cm and 10−20 cm layers of Eucalyptus maideni forest were significantly higher than those in Pinus yunnanensis forest and secondary forest (P < 0.05). The available phosphorus (AP) content in 0−10 cm soil layer of secondary forest was significantly higher than that in Pinus yunnanensis forest and Eucalyptus maideni forest (P < 0.05). The contents of soil orgenic carbon (SOC) and ammonium nitrogen (AN) showed the law of secondary forest > Pinus yunnanensis forest > Eucalyptus maideni forest. (2) The activity of acid phosphatase and urease in the 0−10 cm soil layer of three woodlands was in the order of secondary forest > Eucalyptus maideni forest > Pinus yunnanensis forest, while the 10−20 cm soil layer showed the opposite law. The highest activities of amylase, cellulase and invertase in 0−10 cm and 10−20 cm soil layers were obtained from secondary forest, followed by Pinus yunnanensis forest and the lowest in Eucalyptus maideni forest. In addition, the soil enzyme activities in the soil layers of the forests were significantly different (P < 0.05), and the soil enzyme activities showed a trend of decreasing with the increase of soil depth. (3) Through the redundancy analysis of soil physicochemical properties and enzyme activities in the three forest lands, the results showed that SOC, AN, AP and pH all had a significant positive correlation with invertase activity. However, TN was significantly negatively correlated with invertase activity. Soil bulk density was negatively correlated with urease and acid phosphatase activities. (4) the Monte Carlo test showed that the order of importance of soil physicochemical properties on soil enzyme activities was: SOC (41.4%) > AN (32.9%) > AP (24.3%) > soil bulk density (12.6%) > TN (7.9%) > pH (5.5%).

ConclusionComprehensive analysis showed that SOC and AN were the main indicators affecting the changes of soil enzyme activity in the study area. The secondary forest is the best in the restoration of soil fertility and enzyme activity in karst faulted basins, while the advantage of Pinus yunnanensis forest is higher than that of Eucalyptus maideni forest.