A major goal of restoration is to recreate self-sustaining historic conditions that maintain biodiversity and ecosystem function. Most traditional restorations are evaluated by assessing plant communities, the foundation of terrestrial ecosystems, with mixed results. As scientists have gained an appreciation for the importance of feedbacks between plants and soil microbes, the use of microbes in restoration has gained renewed interest both as a tool for restoration and as an indicator of restoration success. Much promise has been made of microbial benefits in restoring degraded ecosystems, therefore it is critical to quantify both the short term and lasting benefits they provide. The goal of this meta-analysis is to quantify the use of microbes, both as bioindicators and as tools, towards ecological restoration goals as defined by the Society for Ecological Restoration (SER). We conducted a Web of Science search for all peer reviewed articles from journals that specialize in fields relevant to ecological restoration, soil biology, and/or applied microbiology. We filtered and categorized the output to produce a dataset of 403 papers categorized among 15 variables such as habitat type, pre restoration use, time since restoration and microbial, plant and ecosystem outcomes.
This meta-analysis examined studies from six continents and nine habitat types. Of the 403 peer reviewed articles analysed, 83 studies manipulated microbial communities with the goal of achieving restoration outcomes, while 320 studies used microbial communities as indicators of restoration success. We predict that the majority of research on the potential benefit of groups like soil microbes are based primarily on plant growth responses. Additionally, we predict that studies will focus on changes in abiotic soil conditions but will not necessarily link ecosystem outcomes to the mechanisms by which they occurred. Our findings will suggest that more field research on microbial additions that directly quantify the long term stability of plant populations or diverse plant communities would improve our understanding of the use of microbes in restoration. Furthermore, we expect that our findings will show that more studies are needed that directly link microbial communities to the mechanism by which ecosystem outcomes are achieved. The data from this meta-analysis will help to identify deficiencies in restorations use of microbes and improve evaluations of microbial effects that better reflect the desired goals of restoration ecology.