Publication bias
Across the entirety of the dataset, as well as within each GC, there was a distinct lack of positive large effect sizes, resulting in asymmetry. Yet, it is difficult to fully understand the type(s) of bias that has caused the asymmetry . It is most likely that the bias is a result of certain experiments never being published , through selective reporting from either authors or journals . However, it is possible that the GCs rarely have a positive effect on soil biodiversity. Thus, in that instance the ‘bias’ is not a true bias, and in theory the results should not be adjusted, as done here. Although we are unable to establish the underlying cause of the bias, adjusting for the bias had minimal significant impact on the outcomes of the meta-analysis (Supplementary Materials, Appendix 2). The results that did significantly change, either by no longer being a significant impact or becoming significant, were those with the least amount of data, and therefore least robust coefficients.