Soil biological activity of abandoned saline fields with different restoration treatments

The characteristics of soil microorganisms are critical in soil restoration and ecosystem health. To a large extent, different restoration methods of vegetation have different effects on the activity of soil microorganisms. The understanding of the characteristics of soil microorganisms under different restoration methods of vegetation is critical for exploring the effects of vegetation restoration on soils and for laying the scientific basis for ecological restoration of abandoned fields. In this study, a field experiment was conducted in saline soil of the alluvial fans of the Manas River Valley, which is largely an arid region. The four treatments were set out in the experiment, including original abandoned field (control), water supplement field, artificial grassland field and plant supplement field. The last three treatments were applied in the original abandoned field. The main aim of the experiment was to study the effects of different restoration models on soil microbial biomass, enzyme activity and soil respiration rate of abandoned saline fields. The results indicated that soil enzyme activity, soil microbial population and soil microbial biomass carbon and nitrogen were significantly enhanced by different vegetation restoration models. Soil microbial biomass carbon and nitrogen under water supplement field, artificial grassland field and planting supplement field were respectively 17.80%, 26.38%, 5.33%, and 7.89%, 12.75%, 21.93% higher than those under original abandoned field. The numbers of soil microbes under the three vegetation restoration treatments were respectively 4.72, 6.04 and 4.56 times that of original abandoned field. Also soil sucrase activity under the three different restoration treatments were respectively 3.4, 3.2 and 7.7 times that of the original abandoned field. Then soil polyphenol oxidase activity under the three different restoration treatments were respectively 1.7, 1.2 and 1.5 times that of the original abandoned field. Similarly, soil urease activity of three different restoration treatments were respectively 11.1%, 52.3% and 37.1% higher than that of the original abandoned field. Among the treatments, soil catalase activity of the water supplement field treatment was highest (1.53 times that of the original abandoned field). The order of changes in soil respiration rate under the three different restoration models of abandoned saline field was artificial grassland field > water supplement field > planting supplement field > original abandon farmland field. Soil respiration rate under artificial grassland field was 52.25% higher than that under the abandoned field. Water supplement and artificial grassland fields of abandoned saline fields in arid regions enhanced the accumulation of soil nutrient and thereby improved soil quality. Correlation analysis showed that among the indexes of the characteristics of soil microorganisms, soil microbial biomass carbon, microbial biomass C/N and soil microbial amount were positive correlated (significant at P < 0.05). Positive correlations were noted between soil respiration rate versus soil urease, microbial population and microbial biomass C (significant at P < 0.05) and negative (but not significant) correlations between soil respiration rate and soil microbial biomass N. Also positive correlations were noted between soil sucrase activity versus the other three soil enzymes (urease, polyphenol oxidase and catalase) and microbial biomass nitrogen (significant at P < 0.05). A positive correlation was noted between soil urease and soil microbial amount (significant atP < 0.05). There was also a positive correlation between soil polyphenol oxidase and soil catalase (significant at P < 0.05). Thus the characteristics of soil microorganisms were interrelated with soil enzymes and soil respiration rate. This suggested that the three factors not only exhibited distinct characteristics but also mutually influenced and interacted during soil conversion. This interaction therefore needed further clarification in further research efforts.