Soil Bacterial Communities Across Tropical Secondary Forest Succession on Different Soil Orders

Abstract:

Human activity has resulted in deforestation and large-scale changes in land cover in tropical systems, which has affected soil resources and the soil microbiome. Because soil bacteria play critical roles in ecosystem processes such as decomposition and nitrification, which contribute to biogeochemical cycles, including the carbon cycle, bacterial community changes have enormous implications. The abandonment of land use activities globally in tropical regions provides the opportunity to analyze how soil bacteria change across forest regrowth in different environments. The objective of this study is to understand how bacterial communities respond to secondary forest succession on former pastures on two different soil orders, Mollisols and Alfisols, which are both sampled in order to account for the wide diversity of soil types. Soil samples (0-10 cm depth) from the Ciales karst region of Puerto Rico were extracted for DNA and amplified with PCR on the 16S rRNA gene. In addition, the samples were analyzed for soil nitrogen concentrations. Our results indicate that there is no clear relationship between overall bacterial community composition and forest successional stage or soil order. The phyla Actinobacteria and Proteobacteria exhibited greater abundances in Mollisol soils and medium-aged (20 - 40 years) forests, respectively. The findings also demonstrated the correlation of increased nitrogen and greater bacterial abundance for Acidobacteria, which shows the importance of nitrogen in shaping soil bacteria community structure, as well as the variability in response of different phyla to nitrogen levels. By analyzing these variables, we seek to gain knowledge on how bacterial communities are affected by land cover change and forest recovery in different soil environments and how these changes influence soil biogeochemical processes and the carbon cycle.