Grasslands are the most at risk ecosystem largely due to agricultural land-use conversion. Ecological restoration is an important way to improve and protect grasslands, particularly in the tallgrass prairie region of North America where less than 4% of prairie remain. Soil microbial communities are an important part of tallgrass prairie communities; yet are not commonly considered in restoration planning and monitoring.
We studied changes in soil microbial communities and their activities in restored tallgrass prairie for the purposes of alternative bioenergy management systems in contrast to traditional row-crops. Specifically, we investigated 3 different management systems: corn, restored prairie, and restored prairie fertilized with nitrogen. Across a 4-year sampling period, we measured microbial community structure, function, and resiliency to drought. We hypothesized that 1) over time different restoration approaches will generate distinct soil microbial communities reflecting the extent of divergence between the plant communities. 2) Across sampling years different restoration approaches will diverge in microbial enzyme activity. 3) Restoration approaches with greater plant and microbial diversity will have more functional redundancy and therefore develop enhanced resiliency to drought.
Results/Conclusions
Our experiment demonstrates that soil microbial communities continue to diverge from row-crop agriculture as prairie restoration progresses showing successful rehabilitation of the belowground community in response to aboveground practices. The higher diversity of the plant community in the prairies was reflected in the microbial communities. In addition, microbial communities were more resilient to drought under the prairie systems than the corn system for both microbial activity and richness. Finally, nitrogen fertilized prairies had the greatest resiliency to drought, reflected in the maintained high microbial diversity and activity.
Our study demonstrates that prairie restoration increases and diversifies microbial communities and the activities of those communities are more resilient to disturbance events. Increasing resiliency, while maintaining productivity, is key to managing alternative crops that are sustainable systems for many uses, including alternative biofuel feedstock. Our multi-year study reveals the benefits of long-term experiments for capturing the dynamic range of microbial mediation of soil carbon and nutrients and the importance of resiliency in both developing sustainable management systems and improving predictive biogeochemical models.