Contrasting Soil Bacterial Community, Diversity, and Function in Two Forests in China

Abstract

Bacteria are the highest abundant microorganisms in the soil. To investigate bacteria community structures, diversity, and functions, contrasting them in four different seasons all the year round with/within two different forest type soils of China. We analyzed soil bacterial community based on 16S rRNA gene sequencing via Illumina HiSeq platform at a temperate deciduous broad-leaved forest (Baotianman, BTM) and a tropical rainforest (Jianfengling, JFL). We obtained 51,137 operational taxonomic units (OTUs) and classified them into 44 phyla and 556 known genera, 18.2% of which had a relative abundance >1%. The composition in each phylum was similar between the two forest sites. Proteobacteria and Acidobacteria were the most abundant phyla in the soil samples between the two forest sites. The Shannon index did not significantly differ among the four seasons at BTM or JFL and was higher at BTM than JFL in each season. The bacteria community at both BTM and JFL showed two significant (P < 0.05) predicted functions related to carbon cycle (anoxygenic photoautotrophy sulfur oxidizing and anoxygenic photoautotrophy) and three significant (P < 0.05) predicted functions related to nitrogen cycle (nitrous denitrificaton, nitrite denitrification, and nitrous oxide denitrification). We provide the basis on how changes in bacterial community composition and diversity leading to differences in carbon and nitrogen cycles at the two forests.

Keywords: bacterial community structure; bacterial diversity; bacterial function; environmental factors; temperate deciduous broad-leaved forest; tropical rainforest.

Figure 1

Map of the study areas. Baotianman National Natural Reserve in Neixiang County, Henan Province, and Jianfengling National Natural Reserve in Ledong County, Hainan Province, China.

Figure 2

Community composition in two forests soil at the phylum level. RS1-2: autumn and winter of 2015 at Baotianman; RS3-4: spring and summer of 2016 at Baotianman; RS5-6: autumn and winter of 2015 at Jiangfengling; RS7-8: spring and summer of 2016 at Jiangfengling.

Figure 3

Redundancy analysis (RDA) of high-throughput sequencing data with soil physiochemical properties. WC, water content; T, temperature; WFPS, water-filled pore space; ${\text{NO}}_3^{-}$-N, nitrate nitrogen; ${\text{NH}}_4^{+}$-N, ammonia nitrogen; DOC, dissolved organic carbon; TC, total carbon; TN, total nitrogen; MBN, microbial biomass nitrogen; and MBC, microbial biomass carbon. Arrow lengths indicate the strength of the relationship between the soil property and the overall microbial community. The direction of the line indicates the direction of increase for a specific soil physiochemical property.

Figure 4

The bacterial Shannon index of the two forest sites. Autumn and winter represent the autumn and winter of 2015, respectively. Spring and summer represent the spring and summer of 2016, respectively. The asterisks represent significant differences between BTM and JFL at the same season (P < 0.05).

Figure 5

Functional groups with significant difference in carbon cycle. Autumn and winter represent the autumn and winter of 2015, respectively. Spring and summer represent the spring and summer of 2016, respectively. The asterisks represent significant differences between BTM and JFL at the same season (P < 0.05). (A) OTU proportions of anoxygenic photoautotrophy sulfur oxidizing. (B) OTU proportions of anoxygenic photoautotrophy.

Figure 6

Functional groups with significant difference in nitrogen cycle. Autumn and winter represent the autumn and winter of 2015, respectively. Spring and summer represent the spring and summer of 2016, respectively. The asterisks represent significant differences between BTM and JFL at the same season (P < 0.05). (A) OTU proportions of nitrous denitrification. (B) OTU proportions of nitrite denitrification. (C) OTU proportions of nitrous oxide denitrification.

Figure 7

Redundancy analysis (RDA) of the predicted FAPROTAX functions asscoated with soil physiochemical properties.(A) Functional groups that are related to carbon cycle. (B) Functional groups that are related to nitrogen cycle. WC, water content; T, temperature; WFPS, water-filled pore space; ${\text{NO}}_3^{-}$-N, nitrate nitrogen; ${\text{NH}}_4^{+}$-N, ammonia nitrogen; DOC, dissolved organic carbon; TC, total carbon; TN, total nitrogen; MBN, microbial biomass nitrogen; and MBC, microbial biomass carbon. Arrow lengths indicate the strength of the relationship between the soil property and the overall microbial community. The direction of the line indicates the direction of increase for a specific soil physiochemical property. RS1-2: autumnand winter of 2015 at Baotianman; RS3-4: springandsummerof 2016 at Baotianman; RS5-6: autumn and winter of 2015 at Jiangfengling; RS7-8: spring and summer of 2016 at Jiangfengling.