The influence of precipitation timing and amount on soil microbial community in a temperate desert ecosystem

Abstract

Introduction: Global climate change may lead to changes in precipitation patterns. This may have a significant impact on the microbial communities present in the soil. However, the way these communities respond to seasonal variations in precipitation, particularly in the context of increased precipitation amounts, is not yet well understood.

Methods: To explore this issue, a five-year (2012-2016) field study was conducted at the northeast boundary of the Ulan Buh Desert, examining the effects of increased precipitation during different periods of the growing season on both bacterial and fungal communities. The study included five precipitation pattern treatments: a control group (C), as well as groups receiving 50 and 100% of the local mean annual precipitation amount (145 mm) during either the early growing season (E50 and E100) or the late growing season (L50 and L100). The taxonomic composition of the soil bacterial and fungal communities was analyzed using Illumina sequencing.

Results: After 5 years, the bacterial community composition had significantly changed in all treatment groups, with soil bacteria proving to be more sensitive to changes in precipitation timing than to increased precipitation amounts within the desert ecosystem. Specifically, the alpha diversity of bacterial communities in the late growing season plots (L50 and L100) decreased significantly, while no significant changes were observed in the early growing season plots (E50 and E100). In contrast, fungal community composition remained relatively stable in response to changes in precipitation patterns. Predictions of bacterial community function suggested that the potential functional taxa in the bacterial community associated with the cycling of carbon and nitrogen were significantly altered in the late growing season (L50 and L100).

Discussion: These findings emphasize the importance of precipitation timing in regulating microbial communities and ecosystem functions in arid regions experiencing increased precipitation amounts.

Keywords: Illumina sequencing; bacterial and fungal communities; precipitation increase; precipitation time; temperate desert.

Figure 1

The alpha diversity of the bacterial community exhibited a declining trend, whereas the alpha diversity of the fungal community did not show significant changes. The alpha-diversity of bacterial (A–D) and fungal (E–H) taxonomic communities under different precipitation treatments are depicted in the box plots. The height of each box represents the range from the lower 1/4 quantile to the upper 1/4 quantile. Outliers are denoted as solid black circles positioned above or below the boxes. Lowercase letters (a, b, c) indicate significant differences across treatments, determined through ANOVA analysis, and post hoc analyses were conducted using Fisher’s least significant difference (LSD) test. Control (C) = ambient precipitation, E50 = ambient precipitation +50% of the local annual average precipitation in the early growing reason, E100 = ambient precipitation +100% of the local annual average precipitation in the early growing reason, L50 = ambient precipitation +50% of the local annual average precipitation in the late growing reason, L100 = ambient precipitation +100% of the local annual average precipitation in the late growing reason.

Figure 2

Nonmetric multidimensional scaling (NMDS) of Bray–Curtis’s dissimilarities highlighted that bacterial (A) and fungal (B) community structures were different among all treatments. Similarity values among the samples were examined via the Adonis and ANOSIM tests, which are shown in each plot. Ellipses in the plots denote 90% confidence intervals. The relative abundances of the dominant bacterial (C) and fungal (D) phyla in all treatments as shown. Further details regarding the differences in bacterial and fungal phyla among treatments can be found in Table 2. There were no significant changes in the relative abundances of fungal phyla.

Figure 3

Spearman’s correlation coefficient analysis of bacterial and fungal communities and alpha diversity indices with environmental factors. The colors represent the magnitude of Spearman’s correlation coefficient r. Darker colors represent larger values of |r|, the more correlated. r > 0, representing positive correlation, is marked in blue. r < 0, representing negative correlation, is marked in red. ns represents p > 0.05; *represents 0.01 < p < 0.05; **represents 0.001 < p < 0.01; ***represents p < 0.001. TC, total carbon; TN, total nitrogen; TP, total phosphorus.

Figure 4

Potential functional taxa with significant variation in bacterial and fungal communities (p < 0.05). Our methods for predicting the potential function of soil bacterial and fungal communities are FAPROTAX and FUNGuild. Lowercase letters (a, b, c) within panels indicate significant differences among the treatments (p < 0.05). These differences were determined using a multiple-comparison test following ANOVA analysis, and post hoc analyses were conducted using Fisher’s least significant difference (LSD) test (p < 0.05).