PLFA analysis of soil microorganism under Robinia pseudoacacia and Pinus tabuliformis plantation in loess area

Objective This paper aims to investigate the effects of artificial vegetation restoration on soil microbial community composition in the loess hilly-gully region, and provide data reference for regional vegetation restoration evaluation.

Method Three typical vegetation types, including Robinia pseudoacacia, Pinus tabuliformis plantation and grassland, were chosen in Jixian County, Shanxi Province of northern China. Soil samples from depth of 0−20 cm and 20−40 cm were collected respectively, and soil microbial community composition was evaluated by phospholipid fatty acid (PLFA) analysis (MIDI-Sherlock system). Based on the PLFA analysis, we studied the differences between soil microbial PLFA contents and soil microbial community after restoration, and further explored the effect of soil chemical properties on soil microbial community structure.

Result Results showed that total PLFAs, biomasses of bacteria, actinomycetes, gram-positive bacteria, arbuscular mycorrhizal fungi and diversity indicators (Shannon-Wiener, Simpson and Pielou index) followed the order of Robinia pseudoacacia > Pinus tabuliformis > grassland (P < 0.05). Meanwhile, the ratio of Saturated fatty acids to Monounsaturated fatty acids (SAT/MONO) in the two plantations was significantly lower than grassland (P < 0.05), which implied that environmental stress on soil microorganisms had reduced. Principal component analysis indicated that soil microbial community structure differed among various vegetation types and soil depths, and that the difference reached a significant level in topsoil (P < 0.05). Redundancy analysis and Pearson correlation analysis showed that soil total nitrogen and pH were the main factors leading to the changes of soil microbial community structure.

Conclusion The restoration of Robinia pseudoacacia, Pinus tabuliformis impacted the diversity of soil microbial community structure significantly, and both typical plantations had positive effect on soil ecosystem restoration. Our findings suggest that Robinia pseudoacacia was more conducive to the improvement of soil microbial ecological environment than Pinus tabuliformis.