Soil abiotic factors are not consistently associated with microbial diversity or organic matter removal intensity in regions of long-term reforestation
Healthy soil structure is necessary for the sustainable management of forest ecosystems. As a major component of the Earth’s biosphere, these forest soil ecosystems play a key role in climate regulation, biogeochemical cycling, and the maintenance of biodiversity. Despite the importance of soil ecosystems, not much is known about the role of soil bacterial communities in mediating the health and productivity of the forest floor, especially in the context of deforestation. Here, we analyzed data obtained from a Long-Term Soil Productivity study to determine the effects of organic matter removal on soil abiotic factors, and the resulting impact on bacterial diversity 10 years after reforestation. By analyzing beta diversity, we found that both geographic location and soil depth were associated with differences in diversity between soil bacterial communities. Further statistical analysis also revealed significant relationships between soil depth and abiotic factors. Higher soil organic carbon, nitrogen content, and moisture content were associated with samples taken from the organic topsoil layer, and soil pH levels were more acidic in organic soil samples compared to mineral soil samples. Alpha diversity and taxonomic abundance analyses indicated that the distribution of bacterial phyla differed between geographic regions, with significantly lower diversity in British Columbia soil communities. We did not find organic matter removal to consistently impact the levels of soil organic carbon, nitrogen content, moisture content, or pH. Similarly, linear regression models for each region indicated minimal associations between soil abiotic factors and bacterial alpha diversity. Overall, these findings provide insight into the association between bacterial community composition and soil abiotic factors across a variety of geographic regions, and the impact of deforestation on these relationships.