Seasonal Change of Microbial Diversity and Its Relation with Soil Chemical Properties in Orchard

This study aimed to determine the microbial diversity of different soil depths (0-5 and 5-20 cm) in a subtropical orchard during different seasons (i.e., Spring, Summer and Autumn) for enrich the knowledgements on micorbes roles in orchard ecosystem balance. In tracking experiments conducted in an orchard (established in 1996), the phospholipid fatty acid (PLFA) biomarker method was employed to know soil microbial system. Total PLFAs concentration did not vary significantly between soil depths but changed between seasons. It peaked in the summer at 258.97 {+/-} 23.48 g g-1 soil from 0-5 cm and at 270.99 {+/-} 58.94 g g-1 soil from 5-20 cm. A total of 33 microbial fatty acid biomarkers were observed and identified in the sampled soil. Quantities of PLFAs for 29 microbe groups varied significantly between seasons, except for 15:0 iso 3OH, 15:1 iso G, 16:0 2OH, and 17:0 iso 3OH. The bacterial PLFAs and fungal and actinomycotic PLFAs in the orchard soil collected in Summer were significantly higher than in the Spring or Autumn (P < 0.01). The number of soil microorganism species (Richness) and the Simpson and Shannon-Wiener indexes were all the highest in summer. The total PLFAs, bacterial PLFAs, fungal PLFAs, actinomycotic PLFAs, Richness, or the Simpson and Shannon-Wiener indexes were all significantly negatively correlated with soil pH, total carbon (TOC), total nitrogen (TN) and cation-exchange capacity (CEC) (P < 0.05).