Decoding seasonal changes: soil parameters and microbial communities in tropical dry deciduous forests

Abstract

In dry deciduous tropical forests, both seasons (winter and summer) offer habitats that are essential ecologically. How these seasonal changes affect soil properties and microbial communities is not yet fully understood. This study aimed to investigate the influence of seasonal fluctuations on soil characteristics and microbial populations. The soil moisture content dramatically increases in the summer. However, the soil pH only gradually shifts from acidic to slightly neutral. During the summer, electrical conductivity (EC) values range from 0.62 to 1.03 ds m^-1, in contrast to their decline in the winter. The levels of soil macronutrients and micronutrients increase during the summer, as does the quantity of soil organic carbon (SOC). A two-way ANOVA analysis reveals limited impacts of seasonal fluctuations and specific geographic locations on the amounts of accessible nitrogen (N) and phosphorus (P). Moreover, dehydrogenase, nitrate reductase, and urease activities rise in the summer, while chitinase, protease, and acid phosphatase activities are more pronounced in the winter. The soil microbes were identified in both seasons through 16S rRNA and ITS (Internal Transcribed Spacer) gene sequencing. Results revealed Proteobacteria and Ascomycota as predominant bacterial and fungal phyla. However, Bacillus, Pseudomonas, and Burkholderia are dominant bacterial genera, and Aspergillus, Alternaria, and Trichoderma are dominant fungal genera in the forest soil samples. Dominant bacterial and fungal genera may play a role in essential ecosystem services such as soil health management and nutrient cycling. In both seasons, clear relationships exist between soil properties, including pH, moisture, iron (Fe), zinc (Zn), and microbial diversity. Enzymatic activities and microbial shift relate positively with soil parameters. This study highlights robust soil-microbial interactions that persist mainly in the top layers of tropical dry deciduous forests in the summer and winter seasons. It provides insights into the responses of soil-microbial communities to seasonal changes, advancing our understanding of ecosystem dynamics and biodiversity preservation.

Keywords: bacteria; forest soil; fungi; seasonal variation; soil parameters.

Figure 1

Pearson correlation matrix of forest soil parameters, including physiological, chemical, mineral, and enzyme data. EC, electric conductivity; SOC, soil organic carbon. (*p < 0.05; **p < 0.01; ***p < 0.001).

Figure 2

Relative abundance of bacterial (A) and fungal (B) genera in forest soil samples of MP, Malva plateau; NV, Narmada valley; and SP, Satpura valley during two seasons (S, Summer and W, Winter).

Figure 3

Sankey diagram showing the distribution of all identified bacterial taxa (A) and fungal taxa (B) at each taxonomic level.

Figure 4

Venn diagrams illustrating the distribution of bacterial (A) and fungal (B) taxa among three locations (MP, Malva plateau; NV, Narmada valley; and SP, Satpura valley) and two seasons (summer and winter).

Figure 5

Linear regression relationship between the diversity (Shannon index) of bacteria and fungi versus soil parameters (pH, moisture; EC, electric conductivity; and SOC, soil organic carbon) during two seasons (summer and winter).

Figure 6

Linear regression relationship between the diversity (Shannon index) of bacteria and fungi versus soil parameters (available N,P, and K) during two seasons (summer and winter).

Figure 7

Linear regression relationship between the diversity (Shannon index) of bacteria and fungi versus soil micronutrients (Cu, Fe, Mn and Zn) during two seasons (summer and winter).

Figure 8

Linear regression relationship between the diversity (Shannon index) of bacteria and fungi versus soil enzymes during two seasons (v).

Figure 9

Pearson correlation heatmap showing the relationships between soil parameters (physiological, chemical, mineral, and enzymes) and the dominant genera of bacteria (top 16) and fungi (top 12). EC, electric conductivity; SOC, soil organic carbon.