Soil organic matter as a proxy for assessing ecosystem change: Insights from soil prokaryotic communities in a successional forest

Soil microbes link aboveground and belowground ecosystem processes by modulating nutrient retention, recycling, and availability to plants. Soil microbes are influenced by biotic and edaphic factors such as forest succession and soil horizon. However, knowledge remains limited about how soil microbial communities respond to forest succession. Here, we used 16S rRNA pyrosequencing to investigate how abundance, diversity, and composition of soil prokaryotic communities changed spatially and across forest successional stages in China's Changbai Mountain region, and related those changes with soil properties evaluated by chemical and spectroscopic methods. Major taxa represented in our forest soil included Acidobacteria, Actinobacteria, Bacteroidetes, Proteobacteria, Verrucomicrobia and Crenarchaeota. The abundance, diversity, and composition of the soil prokaryotic communities varied with forest succession and soil horizon, demonstrating that soil prokaryotic communities are shaped by biotic-abiotic interactions associated with a changing environment. Community responses were related with soil pH and resource availability. Changes in soil organic matter (SOM) composition were particularly strong drivers of the transition between copiotrophic and oligotrophic of microbial communities during forest succession. This study further indicates that changes in microbial community structures paralleling changes in ecosystem functions can be inferred through shifty SOM revealed by mid-IR spectroscopy.