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

Abstract

15This study aimed to determine the microbial diversity of different soil depths (0-5 and 5-20 cm) in a subtropical 16 orchard during different seasons (i.e., Spring, Summer and Autumn) for enrich the knowledgements on micorbes 17 roles in orchard ecosystem balance. In tracking experiments conducted in an orchard (established in 1996), the 18 phospholipid fatty acid (PLFA) biomarker method was employed to know soil microbial system. Total PLFAs 19 concentration did not vary significantly between soil depths but changed between seasons. It peaked in the 20 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 21 microbial fatty acid biomarkers were observed and identified in the sampled soil. Quantities of PLFAs for 29 22 microbe groups varied significantly between seasons, except for 15:0 iso 3OH, 15:1 iso G, 16:0 2OH, and 17:0 23 iso 3OH. The bacterial PLFAs and fungal and actinomycotic PLFAs in the orchard soil collected in Summer were 24 significantly higher than in the Spring or Autumn (P < 0.01). The number of soil microorganism species (Richness) 25 and the Simpson and Shannon-Wiener indexes were all the highest in summer. The total PLFAs, bacterial PLFAs, 26 fungal PLFAs, actinomycotic PLFAs, Richness, or the Simpson and Shannon-Wiener indexes were all 27 significantly negatively correlated with soil pH, total carbon (TOC), total nitrogen (TN) and cation-exchange 28 capacity (CEC) (P < 0.05). 29The orchard ecosystem is important for fruit production and carbon sequestration, biodiversity decreases [1] and 32 soil erosion [2], and pollution [3,4]. Hence, maintaining a balanced orchard ecosystem is essential. Soil microbes 33 are essential for the functioning of terrestrial ecosystems because they play a unique and indispensable role in 34 ecosystem balance [5]. 35Soil microbial community change by soil quality evolution because of long-term management. The interaction 36 between microbes and soil quality is very complex. It is reflected in effects on microbial diversity of chemical 37 properties change [6][7][8][9][10][11]. Spatial and temporal distribution of microbial community have some value information 38 to explain the interaction [12][13][14][15][16][17][18]. However, few clear information had be found by observation on spatial and 39 temporal distribution of microbial community in subtropical orchard. 40Thus, we hypothesized that height seasonal temperature and moisture variation and vertical soil chemical 41 properties change would lead to obvious differences in spatial and temporal distribution of microbial community in 42 subtropical orchard. To demonstrate seasonal and vertical changes in microbial diversity and the links between 43 soil microbial diversity and soil chemical properties in a subtropical orchard, PLFA was employed to monitor 44 microorganism quantity and diversity in orchard soils under different seasons in the hilly red soil of the subtropical 45 zone in southern China. The observations of this study regarding ecologic...